Rebuild UI as a scriptable element tree, archive the old system

The old UI system (X-macro static element list, hand-authored C
screens/widgets/focus stack) is archived under archive/ rather than
deleted, since it's a useful reference during the rewrite.

New native UI element pool (src/dusk/ui): a flat UI_ELEMENTS[128] pool
of tagged-union elements (Label, Rectangle, Scripted), a real
persistent parent/child tree (children[8] per element, cycle- and
capacity-checked uiElementSetParent), always-fresh worldX/worldY
(cheap enough to recompute on every read, no dirty-flag cache needed),
and cascading dispose. Rendering stays manual/immediate: a scripted
element with no render() override auto-renders its children by
default, but overriding render() takes full control (an override must
call renderChildren() itself to opt back in) -- this is deliberately
preserved end to end via a render()-shadow trampoline so overriding
render() always keeps working the same way regardless of how a node
is reached.

New scripting layer (src/dusk/script/module/ui): UIElement/Label/
Rectangle JS classes (Label/Rectangle share UIElement's prototype via
manual chaining, not JS `extends`), exposing x/y/worldX/worldY/parent/
add()/remove()/render()/renderChildren()/dispose(). UI.add()/
UI.remove() manage top-level render roots, mutually exclusive with
being someone's child.

Also: Scene gains a lateUpdate() hook (called once per frame after
every other update, for things like camera-follow that need to react
to where everything else ended up); several duskrpg call sites
(cutscene items, entityinteractable, entityplayer) that depended on
the now-archived RPG textbox are stubbed to console output instead of
a dialogue box, pending the new UI reaching that far.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

archive/dusk/ui/CMakeLists.txt

@@ -0,0 +1,18 @@
+# Copyright (c) 2026 Dominic Masters
+# 
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+add_subdirectory(debug)
+add_subdirectory(frame)
+add_subdirectory(focus)
+add_subdirectory(overlay)
+add_subdirectory(transition)
+add_subdirectory(widget)
+
+# Sources
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    ui.c
+    uielement.c
+)

archive/dusk/ui/debug/CMakeLists.txt

@@ -0,0 +1,10 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uiconsole.c
+    uifps.c
+)

archive/dusk/ui/debug/uiconsole.c

@@ -0,0 +1,138 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiconsole.h"
+#include "assert/assert.h"
+#include "console/console.h"
+#include "display/screen/screen.h"
+#include "display/text/text.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+#include "display/mesh/mesh.h"
+#include "util/memory.h"
+
+typedef struct {
+  mesh_t mesh;
+  bool_t built;
+  meshvertex_t vertices[UI_CONSOLE_CACHE_VERTEX_MAX];
+  int32_t vertexCount;
+  int32_t cachedScanX;
+  int32_t cachedScanY;
+} uiconsolecache_t;
+
+uiconsolecache_t UI_CONSOLE_CACHE;
+
+errorret_t uiConsoleDraw(void) {
+  if(!CONSOLE.visible) errorOk();
+
+  if(
+    CONSOLE.dirty ||
+    UI_CONSOLE_CACHE.cachedScanX != SCREEN.scanX ||
+    UI_CONSOLE_CACHE.cachedScanY != SCREEN.scanY
+  ) {
+    errorChain(uiConsoleRebuild());
+  }
+
+  if(UI_CONSOLE_CACHE.vertexCount == 0) errorOk();
+
+  shadermaterial_t material = {
+    .unlit = {
+      .color = COLOR_RED,
+      .texture = FONT_DEFAULT.texture
+    }
+  };
+
+  errorChain(shaderBind(&SHADER_UNLIT));
+  errorChain(shaderSetMaterial(&SHADER_UNLIT, &material));
+  return meshDraw(&UI_CONSOLE_CACHE.mesh, 0, UI_CONSOLE_CACHE.vertexCount);
+}
+
+errorret_t uiConsoleRebuild(void) {
+  int32_t spriteCount = 0;
+  for(uint32_t i = 0; i < CONSOLE_HISTORY_MAX; i++) {
+    char_t c;
+    int32_t j = 0;
+    while((c = CONSOLE.line[i][j++]) != '\0') {
+      if(c != ' ' && c != '\n') spriteCount++;
+    }
+  }
+
+  assertTrue(
+    spriteCount <= UI_CONSOLE_CACHE_GLYPH_MAX,
+    "Console history exceeds fixed cache capacity"
+  );
+
+  const int32_t vertexCount = spriteCount * QUAD_VERTEX_COUNT;
+  UI_CONSOLE_CACHE.vertexCount = vertexCount;
+
+  if(vertexCount > 0) {
+    const float_t lineH = (float_t)FONT_DEFAULT.tileset->tileHeight;
+    const float_t charW = (float_t)FONT_DEFAULT.tileset->tileWidth;
+
+    int32_t index = 0;
+    int32_t row = 0;
+    for(uint32_t i = 0; i < CONSOLE_HISTORY_MAX; i++) {
+      float_t posX = (float_t)SCREEN.scanX;
+      float_t posY = (float_t)SCREEN.scanY + lineH * (float_t)row;
+
+      char_t c;
+      int32_t j = 0;
+      while((c = CONSOLE.line[i][j++]) != '\0') {
+        if(c == '\n') {
+          posX = (float_t)SCREEN.scanX;
+          posY += lineH;
+          row++;
+          continue;
+        }
+
+        if(c == ' ') {
+          posX += charW;
+          continue;
+        }
+
+        const spritebatchsprite_t sprite = textGetSprite(
+          (vec2){ posX, posY }, c, &FONT_DEFAULT
+        );
+        spriteBatchBufferToMesh(
+          &sprite, 1,
+          &UI_CONSOLE_CACHE.vertices[index], QUAD_VERTEX_COUNT
+        );
+
+        index += QUAD_VERTEX_COUNT;
+        posX += charW;
+      }
+
+      row++;
+    }
+
+    if(!UI_CONSOLE_CACHE.built) {
+      errorChain(meshInit(
+        &UI_CONSOLE_CACHE.mesh,
+        QUAD_PRIMITIVE_TYPE,
+        UI_CONSOLE_CACHE_VERTEX_MAX,
+        UI_CONSOLE_CACHE.vertices
+      ));
+      UI_CONSOLE_CACHE.built = true;
+    } else {
+      errorChain(meshFlush(&UI_CONSOLE_CACHE.mesh, 0, vertexCount));
+    }
+  }
+
+  UI_CONSOLE_CACHE.cachedScanX = SCREEN.scanX;
+  UI_CONSOLE_CACHE.cachedScanY = SCREEN.scanY;
+  CONSOLE.dirty = false;
+  errorOk();
+}
+
+errorret_t uiConsoleDispose(void) {
+  if(UI_CONSOLE_CACHE.built) {
+    errorChain(meshDispose(&UI_CONSOLE_CACHE.mesh));
+  }
+
+  memoryZero(&UI_CONSOLE_CACHE, sizeof(uiconsolecache_t));
+  errorOk();
+}

archive/dusk/ui/debug/uiconsole.h

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/mesh/quad.h"
+
+// Fixed capacity for the console's cached glyph mesh, in glyphs -- the
+// mesh/vertex buffer is sized to this once and never grown/shrunk, so
+// history producing more non-space characters than this asserts (see
+// uiConsoleRebuild) instead of reallocating.
+#define UI_CONSOLE_CACHE_GLYPH_MAX 512
+#define UI_CONSOLE_CACHE_VERTEX_MAX (\
+  UI_CONSOLE_CACHE_GLYPH_MAX * QUAD_VERTEX_COUNT \
+)
+
+/**
+ * Renders the console history into the scan-safe area, drawing a mesh
+ * that is only rebuilt when the history changes or the scan-safe origin
+ * moves, rather than rebuffering vertices every frame. No-ops when the
+ * console is not visible.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiConsoleDraw(void);
+
+/**
+ * Rebuilds the cached mesh for the console's current history and
+ * scan-safe origin. Called automatically by uiConsoleDraw() whenever
+ * needed; only needs calling directly to force an immediate rebuild.
+ * The underlying vertex buffer is a fixed-size array (see
+ * UI_CONSOLE_CACHE_VERTEX_MAX) -- asserts if the history produces more
+ * glyphs than that capacity, rather than growing it.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiConsoleRebuild(void);
+
+/**
+ * Frees the mesh and vertex buffer built up by uiConsoleDraw().
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiConsoleDispose(void);

archive/dusk/ui/debug/uifps.c

@@ -0,0 +1,78 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uifps.h"
+#include "time/time.h"
+#include "util/string.h"
+#include "display/text/text.h"
+#include "display/screen/screen.h"
+#include "engine/engine.h"
+
+uifps_t UIFPS;
+
+errorret_t uiFPSInit() {
+  uiLabelInit(&UIFPS.fpsLabel, &FONT_DEFAULT);
+  uiLabelInit(&UIFPS.versionLabel, &FONT_DEFAULT);
+  uiLabelSetText(&UIFPS.versionLabel, ENGINE.version);
+  uiLabelSetColor(&UIFPS.versionLabel, color(255, 255, 255, 128));
+  errorOk();
+}
+
+errorret_t uiFPSDraw() {
+  char_t fpsText[32];
+
+  // Get now.
+  dusktimeepoch_t now = timeGetEpoch();
+  double_t delta = now.time - UIFPS.lastTick.time;
+  UIFPS.lastTick = now;
+
+  // Raw current FPS
+  float_t fps = delta > 0 ? 1.0 / delta : 0.0;
+
+  // Average FPS using exponential moving average
+  const float_t alpha = 0.1f; // Smoothing factor
+  if(UIFPS.fpsAverage == 0.0f) {
+    UIFPS.fpsAverage = fps; // Initialize average on first run
+  } else {
+    UIFPS.fpsAverage = alpha * fps + (1.0f - alpha) * UIFPS.fpsAverage;
+  }
+
+  snprintf(
+    fpsText,
+    sizeof(fpsText),
+    "%.1f/%.1fms",
+    UIFPS.fpsAverage,
+    delta * 1000.0f
+  );
+
+  color_t textColor;
+  if(fps >= 55.0f) {
+    textColor = COLOR_GREEN;
+  } else if(fps >= 45.0f) {
+    textColor = COLOR_YELLOW;
+  } else {
+    textColor = COLOR_RED;
+  }
+
+  uiLabelSetColor(&UIFPS.fpsLabel, textColor);
+  if(stringCompare(fpsText, UIFPS.fpsLabel.text) != 0) {
+    uiLabelSetText(&UIFPS.fpsLabel, fpsText);
+  }
+  errorChain(uiLabelDraw(
+    &UIFPS.fpsLabel, (float_t)SCREEN.scanX, (float_t)SCREEN.scanY
+  ));
+
+  int32_t versionWidth, versionHeight;
+  uiLabelGetSize(&UIFPS.versionLabel, &versionWidth, &versionHeight);
+  errorChain(uiLabelDraw(
+    &UIFPS.versionLabel,
+    (float_t)(SCREEN.scanX + SCREEN.scanWidth - versionWidth),
+    (float_t)(SCREEN.scanY + SCREEN.scanHeight - versionHeight)
+  ));
+
+  errorOk();
+}

archive/dusk/ui/debug/uifps.h

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "time/timeepoch.h"
+#include "ui/widget/uilabel.h"
+
+typedef struct {
+  dusktimeepoch_t lastTick;
+  float_t fpsAverage;
+  uilabel_t fpsLabel;
+  uilabel_t versionLabel;
+} uifps_t;
+
+extern uifps_t UIFPS;
+
+/**
+ * Initializes the FPS counter, caching the (static) version label.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFPSInit();
+
+/**
+ * Draws the FPS counter on the screen, and also does the update (for now).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFPSDraw();

archive/dusk/ui/focus/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uifocus.c
+)

archive/dusk/ui/focus/uifocus.c

@@ -0,0 +1,190 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uifocus.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "input/input.h"
+#include "time/time.h"
+
+const uifocusdirmap_t UI_FOCUS_DIR_MAP[] = {
+  { INPUT_BIND_UP,    UI_FOCUS_DIRECTION_UP,     0, -1 },
+  { INPUT_BIND_DOWN,  UI_FOCUS_DIRECTION_DOWN,   0,  1 },
+  { INPUT_BIND_LEFT,  UI_FOCUS_DIRECTION_LEFT,  -1,  0 },
+  { INPUT_BIND_RIGHT, UI_FOCUS_DIRECTION_RIGHT,  1,  0 },
+  { INPUT_BIND_NULL,  UI_FOCUS_DIRECTION_NONE,   0,  0 },
+};
+
+uifocus_t UI_FOCUS;
+
+void uiFocusInit(void) {
+  memoryZero(&UI_FOCUS, sizeof(uifocus_t));
+}
+
+uifocusitem_t * uiFocusPush(
+  const uint8_t cols,
+  const uint8_t rows,
+  uifocusitemcallback_t selected,
+  uifocusitemcallback_t changed,
+  uifocusitemcallback_t closed,
+  uifocusitemdirectioncallback_t direction,
+  void *user
+) {
+  assertTrue(
+    UI_FOCUS.count < UI_FOCUS_STACK_MAX,
+    "UI focus stack overflow"
+  );
+  assertTrue(cols > 0, "Focus item cols must be > 0");
+  assertTrue(rows > 0, "Focus item rows must be > 0");
+
+  uifocusitem_t *item = &UI_FOCUS.items[UI_FOCUS.count];
+  memoryZero(item, sizeof(uifocusitem_t));
+  item->cols = cols;
+  item->rows = rows;
+  item->selected = selected;
+  item->changed = changed;
+  item->closed = closed;
+  item->direction = direction;
+  item->user = user;
+  UI_FOCUS.count++;
+  UI_FOCUS.pushedThisTick = true;
+  if(item->changed != NULL) item->changed(item);
+  return item;
+}
+
+void uiFocusPop(void) {
+  assertTrue(UI_FOCUS.count > 0, "UI focus stack underflow");
+ 
+  uifocusitem_t *item = &UI_FOCUS.items[UI_FOCUS.count - 1];
+  if(item->closed != NULL) item->closed(item);
+  UI_FOCUS.count--;
+}
+
+void uiFocusPopItem(uifocusitem_t *item) {
+  assertTrue(UI_FOCUS.count > 0, "UI focus stack underflow");
+  assertTrue(item >= UI_FOCUS.items, "Item is not on the focus stack");
+  assertTrue(
+    item < UI_FOCUS.items + UI_FOCUS.count,
+    "Item is not on the focus stack"
+  );
+
+  while(&UI_FOCUS.items[UI_FOCUS.count - 1] != item) {
+    uiFocusPop();
+  }
+  uiFocusPop();
+}
+
+void uiFocusSetPosition(uifocusitem_t *item, const uint8_t x, const uint8_t y) {
+  assertTrue(UI_FOCUS.count > 0, "No active focus item");
+  assertTrue(item->cols > 0, "Focus item cols must be > 0");
+  assertTrue(item->rows > 0, "Focus item rows must be > 0");
+
+  uint8_t newX = x % item->cols;
+  uint8_t newY = y % item->rows;
+
+  if(item->changed != NULL) {
+    uint8_t oldX = item->x;
+    uint8_t oldY = item->y;
+    item->x = newX;
+    item->y = newY;
+    if(!item->changed(item)) {
+      item->x = oldX;
+      item->y = oldY;
+    }
+    return;
+  }
+
+  item->x = newX;
+  item->y = newY;
+}
+
+void uiFocusMoveDirection(
+  uifocusitem_t *item,
+  const uifocusdirection_t dir
+) {
+  for(
+    const uifocusdirmap_t *m = UI_FOCUS_DIR_MAP;
+    m->action != INPUT_BIND_NULL;
+    m++
+  ) {
+    if(m->direction != dir) continue;
+
+    uint8_t x = (uint8_t)(item->x + m->dx);
+    uint8_t y = (uint8_t)(item->y + m->dy);
+    uiFocusSetPosition(item, x, y);
+    break;
+  }
+}
+
+void uiFocusHandleDirection(
+  uifocusitem_t *item,
+  const uifocusdirection_t dir
+) {
+  if(item->direction != NULL && item->direction(item, dir)) return;
+  uiFocusMoveDirection(item, dir);
+}
+
+void uiFocusUpdate(void) {
+  if(UI_FOCUS.count == 0) return;
+
+  #ifdef DUSK_TIME_DYNAMIC
+    if(TIME.dynamicUpdate) return;
+  #endif
+
+  if(UI_FOCUS.pushedThisTick) {
+    UI_FOCUS.pushedThisTick = false;
+    return;
+  }
+
+  uifocusitem_t *item = &UI_FOCUS.items[UI_FOCUS.count - 1];
+
+  if(inputPressed(INPUT_BIND_ACCEPT)) {
+    if(item->selected != NULL) item->selected(item);
+    return;
+  }
+
+  if(inputPressed(INPUT_BIND_CANCEL)) {
+    uiFocusPop();
+    return;
+  }
+
+  for(
+    const uifocusdirmap_t *m = UI_FOCUS_DIR_MAP;
+    m->action != INPUT_BIND_NULL;
+    m++
+  ) {
+    if(!inputPressed(m->action)) continue;
+    UI_FOCUS.direction = m->direction;
+    UI_FOCUS.timeHeld = 0.0f;
+    uiFocusHandleDirection(item, m->direction);
+    return;
+  }
+
+  bool_t held = false;
+  for(
+    const uifocusdirmap_t *m = UI_FOCUS_DIR_MAP;
+    m->action != INPUT_BIND_NULL;
+    m++
+  ) {
+    if(m->direction != UI_FOCUS.direction) continue;
+    held = inputIsDown(m->action);
+    break;
+  }
+
+  if(!held) {
+    UI_FOCUS.direction = UI_FOCUS_DIRECTION_NONE;
+    UI_FOCUS.timeHeld = 0.0f;
+    return;
+  }
+
+  UI_FOCUS.timeHeld += TIME.delta;
+
+  if(UI_FOCUS.timeHeld < UI_FOCUS_HOLD_DELAY) return;
+  if(UI_FOCUS.timeHeld < UI_FOCUS_HOLD_DELAY + UI_FOCUS_HOLD_REPEAT) return;
+  UI_FOCUS.timeHeld = UI_FOCUS_HOLD_DELAY;
+  uiFocusHandleDirection(item, UI_FOCUS.direction);
+}

archive/dusk/ui/focus/uifocus.h

@@ -0,0 +1,133 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "uifocusitem.h"
+#include "input/inputaction.h"
+
+/** Maximum depth of the focus stack. */
+#define UI_FOCUS_STACK_MAX 8
+
+/**
+ * How long a direction must be held before repeating begins, in seconds.
+ */
+#define UI_FOCUS_HOLD_DELAY 0.5f
+
+/**
+ * Interval between repeated moves while a direction is held, in seconds.
+ */
+#define UI_FOCUS_HOLD_REPEAT 0.1f
+
+typedef struct {
+  inputbind_t action;
+  uifocusdirection_t direction;
+  int8_t dx;
+  int8_t dy;
+} uifocusdirmap_t;
+
+/**
+ * Mapping of input actions to focus directions, terminated by an
+ * entry with action == INPUT_BIND_NULL.
+ */
+extern const uifocusdirmap_t UI_FOCUS_DIR_MAP[];
+
+/**
+ * A stack of focused UI items. Push an item when a widget captures
+ * focus; pop it when focus is released. The topmost item is always
+ * the active focus context.
+ */
+typedef struct {
+  uifocusitem_t items[UI_FOCUS_STACK_MAX];
+  uint8_t count;
+  uifocusdirection_t direction;
+  float_t timeHeld;
+  bool_t pushedThisTick;
+} uifocus_t;
+
+extern uifocus_t UI_FOCUS;
+
+/**
+ * Initializes the focus system, zeroing all state.
+ */
+void uiFocusInit(void);
+
+/**
+ * Pushes a new focus item onto the stack with the given grid dimensions
+ * and callbacks. x and y are initialized to 0.
+ *
+ * @param cols      Number of columns in the focus grid.
+ * @param rows      Number of rows in the focus grid.
+ * @param selected  Called when the user selects the focused cell.
+ * @param changed   Called when the focused cell position changes.
+ * @param closed    Called when this focus item is popped.
+ * @param direction Called on a direction press/hold before the default
+ *                  cell-to-cell movement is applied; may be NULL.
+ * @param user      Arbitrary pointer stored on the item before changed fires.
+ * @returns Pointer to the newly pushed focus item.
+ */
+uifocusitem_t * uiFocusPush(
+  const uint8_t cols,
+  const uint8_t rows,
+  uifocusitemcallback_t selected,
+  uifocusitemcallback_t changed,
+  uifocusitemcallback_t closed,
+  uifocusitemdirectioncallback_t direction,
+  void *user
+);
+
+/**
+ * Pops the topmost focus item from the stack, invoking its closed
+ * callback if one is set.
+ */
+void uiFocusPop(void);
+
+/**
+ * Pops an item and anything that was pushed after it from the focus stack.
+ * 
+ * @param item The focus item to pop to. Must be on the stack.
+ */
+void uiFocusPopItem(uifocusitem_t *item);
+
+/**
+ * Manually sets the cursor position of the topmost focus item and
+ * fires its changed callback.
+ *
+ * @param x Column to move to.
+ * @param y Row to move to.
+ */
+void uiFocusSetPosition(uifocusitem_t *item, const uint8_t x, const uint8_t y);
+
+/**
+ * Moves the topmost focus item one step in the given direction,
+ * wrapping at the grid edges, and fires its changed callback.
+ *
+ * @param item The focus item to move.
+ * @param dir Direction to move.
+ */
+void uiFocusMoveDirection(
+  uifocusitem_t *item,
+  const uifocusdirection_t dir
+);
+
+/**
+ * Handles a direction press/hold for the given item: gives the item's
+ * direction callback (if any) first refusal, falling back to the
+ * default cell-to-cell movement if it's unset or returns false.
+ *
+ * @param item The focus item to move.
+ * @param dir Direction that was pressed or held.
+ */
+void uiFocusHandleDirection(
+  uifocusitem_t *item,
+  const uifocusdirection_t dir
+);
+
+/**
+ * Updates the focus system. Handles first-press movement and
+ * held-direction repeating. Called once per game tick.
+ */
+void uiFocusUpdate(void);

archive/dusk/ui/focus/uifocusitem.h

@@ -0,0 +1,57 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "dusk.h"
+
+typedef struct uifocusitem_s uifocusitem_t;
+
+typedef enum {
+  UI_FOCUS_DIRECTION_NONE,
+  UI_FOCUS_DIRECTION_UP,
+  UI_FOCUS_DIRECTION_DOWN,
+  UI_FOCUS_DIRECTION_LEFT,
+  UI_FOCUS_DIRECTION_RIGHT
+} uifocusdirection_t;
+
+/**
+ * Callback invoked when a focus item's selected cell changes.
+ *
+ * @param item The focus item that changed.
+ */
+typedef bool_t (*uifocusitemcallback_t)(const uifocusitem_t *item);
+
+/**
+ * Callback invoked when a direction is pressed or held-repeated while
+ * this item is focused, before the default cell-to-cell movement is
+ * applied.
+ *
+ * @param item The focus item that is currently focused.
+ * @param direction The direction that was pressed.
+ * @returns True if the direction was fully handled and the default
+ * grid movement should be skipped; false to fall through to it.
+ */
+typedef bool_t (*uifocusitemdirectioncallback_t)(
+  const uifocusitem_t *item,
+  const uifocusdirection_t direction
+);
+
+/**
+ * A single entry on the UI focus stack. Tracks the focused cell
+ * within a grid of cols x rows, and the current x/y position.
+ */
+struct uifocusitem_s {
+  uint8_t cols;
+  uint8_t rows;
+  uint8_t x;
+  uint8_t y;
+  uifocusitemcallback_t selected;
+  uifocusitemcallback_t changed;
+  uifocusitemcallback_t closed;
+  uifocusitemdirectioncallback_t direction;
+  void *user;
+};

archive/dusk/ui/frame/CMakeLists.txt

@@ -0,0 +1,12 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uiframe.c
+    uiconfirm.c
+)
+
+add_subdirectory(settings)

archive/dusk/ui/frame/settings/CMakeLists.txt

@@ -0,0 +1,13 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uisettings.c
+    uisettingsgeneral.c
+    uisettingsinput.c
+    uisettingsdisplay.c
+    uisettingsaudio.c
+)

archive/dusk/ui/frame/settings/uisettings.c

@@ -0,0 +1,248 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uisettings.h"
+#include "uisettingsgeneral.h"
+#include "uisettingsinput.h"
+#include "uisettingsdisplay.h"
+#include "uisettingsaudio.h"
+#include "ui/frame/uiframe.h"
+#include "ui/frame/uiconfirm.h"
+#include "util/memory.h"
+#include "display/text/text.h"
+#include "display/screen/screen.h"
+#include "assert/assert.h"
+#include "locale/localemanager.h"
+#include "asset/loader/locale/assetlocaleloader.h"
+
+uisettings_t UI_SETTINGS;
+
+uisettingstabdef_t UI_SETTINGS_TAB_DEFS[UI_SETTINGS_TAB_COUNT] = {
+  {
+    .localeId = "ui.settings.tabs.general",
+    .init = uiSettingsGeneralInit,
+    .menu = (uimenu_t *)&UI_SETTINGS.data,
+    .load = uiSettingsGeneralLoad,
+    .apply = uiSettingsGeneralApply,
+    .hasChanges = uiSettingsGeneralHasChanges
+  },
+
+  {
+    .localeId = "ui.settings.tabs.input",
+    .init = uiSettingsInputInit,
+    .menu = (uimenu_t *)&UI_SETTINGS.data,
+    .load = uiSettingsInputLoad,
+    .apply = uiSettingsInputApply,
+    .hasChanges = uiSettingsInputHasChanges
+  },
+
+  {
+    .localeId = "ui.settings.tabs.display",
+    .init = uiSettingsDisplayInit,
+    .menu = (uimenu_t *)&UI_SETTINGS.data,
+    .load = uiSettingsDisplayLoad,
+    .apply = uiSettingsDisplayApply,
+    .hasChanges = uiSettingsDisplayHasChanges
+  },
+
+  {
+    .localeId = "ui.settings.tabs.audio",
+    .init = uiSettingsAudioInit,
+    .menu = (uimenu_t *)&UI_SETTINGS.data,
+    .load = uiSettingsAudioLoad,
+    .apply = uiSettingsAudioApply,
+    .hasChanges = uiSettingsAudioHasChanges
+  }
+};
+
+static uisettingstabdef_t UI_SETTINGS_TOP_DEF = {
+  .menu = &UI_SETTINGS.tabsMenu,
+  .load = uiSettingsLoad,
+  .hasChanges = uiSettingsHasChanges
+};
+
+static uisettingstabdef_t *UI_SETTINGS_PENDING_DISCARD = NULL;
+static uisettingstabdef_t *UI_SETTINGS_ACTIVE_TAB = NULL;
+
+errorret_t uiSettingsActivateTab(uisettingstabdef_t *def) {
+  if(def == UI_SETTINGS_ACTIVE_TAB) errorOk();
+
+  errorChain(def->init(&UI_SETTINGS.data));
+  def->menu->user = def;
+  def->load();
+  UI_SETTINGS_ACTIVE_TAB = def;
+
+  errorOk();
+}
+
+void uiSettingsTabChanged(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  if(index >= UI_SETTINGS_TAB_COUNT) return;
+  errorCatch(uiSettingsActivateTab(&UI_SETTINGS_TAB_DEFS[index]));
+}
+
+void uiSettingsTabSelected(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  if(index >= UI_SETTINGS_TAB_COUNT) return;
+
+  uisettingstabdef_t *def = &UI_SETTINGS_TAB_DEFS[index];
+  errorCatch(uiSettingsActivateTab(def));
+  uiMenuOpen(def->menu);
+}
+
+errorret_t uiSettingsInit(void) {
+  memoryZero(&UI_SETTINGS, sizeof(uisettings_t));
+  UI_SETTINGS_ACTIVE_TAB = NULL;
+
+  for(uint8_t i = 0; i < UI_SETTINGS_TAB_COUNT; i++) {
+    errorChain(assetLocaleGetString(
+      &LOCALE.entry->data.locale,
+      UI_SETTINGS_TAB_DEFS[i].localeId,
+      0,
+      UI_SETTINGS.tabLabels[i],
+      UI_SETTINGS_TAB_LABEL_MAX
+    ));
+  }
+
+  MENU_BEGIN(
+    &UI_SETTINGS.tabsMenu, UI_SETTINGS.tabs, uiSettingsTabSelected,
+    uiSettingsDiscardMenuClosed, uiSettingsTabChanged
+  );
+  for(uint8_t i = 0; i < UI_SETTINGS_TAB_COUNT; i++) {
+    MENU_TAB(UI_SETTINGS.tabLabels[i]);
+  }
+  MENU_END(UI_SETTINGS.tabs, menuIndex);
+
+  UI_SETTINGS.tabsMenu.user = &UI_SETTINGS_TOP_DEF;
+
+  errorChain(assetLocaleGetString(
+    &LOCALE.entry->data.locale,
+    "ui.settings.apply",
+    0,
+    UI_SETTINGS.applyLabel,
+    UI_SETTINGS_APPLY_LABEL_MAX
+  ));
+
+  errorChain(uiSettingsActivateTab(&UI_SETTINGS_TAB_DEFS[0]));
+
+  errorOk();
+}
+
+errorret_t uiSettingsDraw(void) {
+  if(!uiMenuIsActive(&UI_SETTINGS.tabsMenu)) errorOk();
+
+  const float_t width = SCREEN.width;
+  const float_t height = SCREEN.height;
+  const float_t x = (float_t)SCREEN.scanX +
+    ((float_t)SCREEN.scanWidth - width) * 0.5f;
+  const float_t y = (float_t)SCREEN.scanY +
+    ((float_t)SCREEN.scanHeight - height) * 0.5f;
+
+  errorChain(uiFrameDrawCached(&UI_SETTINGS.frameCache, x, y, width, height));
+
+  const float_t contentX = x + UI_FRAME_START_X;
+  const float_t contentY = y + UI_FRAME_START_Y;
+  const float_t contentWidth = width - (UI_FRAME_START_X * 2);
+  const float_t contentHeight = height - (UI_FRAME_START_Y * 2);
+
+  errorChain(uiMenuDraw(
+    &UI_SETTINGS.tabsMenu,
+    contentX,
+    contentY,
+    contentWidth,
+    contentHeight
+  ));
+
+  const float_t tabsRowHeight = (float_t)FONT_DEFAULT.tileset->tileHeight;
+  const float_t pageY = contentY + tabsRowHeight + UI_FRAME_PADDING_Y;
+  const float_t pageHeight = contentHeight - tabsRowHeight - UI_FRAME_PADDING_Y;
+
+  if(UI_SETTINGS_ACTIVE_TAB != NULL) {
+    errorChain(uiMenuDraw(
+      UI_SETTINGS_ACTIVE_TAB->menu, contentX, pageY, contentWidth, pageHeight
+    ));
+  }
+
+  errorOk();
+}
+
+errorret_t uiSettingsUpdate(void) {
+  if(!UI_SETTINGS_PENDING_DISCARD) errorOk();
+
+  uisettingstabdef_t *def = UI_SETTINGS_PENDING_DISCARD;
+  UI_SETTINGS_PENDING_DISCARD = NULL;
+
+  return uiSettingsDiscardUpdate(def);
+}
+
+bool_t uiSettingsIsOpen(void) {
+  return uiMenuIsActive(&UI_SETTINGS.tabsMenu);
+}
+
+void uiSettingsOpen() {
+  uiSettingsLoad();
+  uiMenuOpen(&UI_SETTINGS.tabsMenu);
+}
+
+void uiSettingsClose() {
+  uiMenuClose(&UI_SETTINGS.tabsMenu);
+}
+
+errorret_t uiSettingsDispose(void) {
+  errorOk();
+}
+
+void uiSettingsLoad(void) {
+  if(UI_SETTINGS_ACTIVE_TAB != NULL) UI_SETTINGS_ACTIVE_TAB->load();
+}
+
+void uiSettingsApply(void) {
+  if(UI_SETTINGS_ACTIVE_TAB != NULL) UI_SETTINGS_ACTIVE_TAB->apply();
+}
+
+bool_t uiSettingsHasChanges(void) {
+  return UI_SETTINGS_ACTIVE_TAB != NULL && UI_SETTINGS_ACTIVE_TAB->hasChanges();
+}
+
+void uiSettingsDiscardMenuClosed(const uimenu_t *menu) {
+  uisettingstabdef_t *def = (uisettingstabdef_t *)menu->user;
+  if(def->hasChanges()) UI_SETTINGS_PENDING_DISCARD = def;
+}
+
+errorret_t uiSettingsDiscardUpdate(uisettingstabdef_t *def) {
+  #define UI_SETTINGS_DISCARD_TEXT_MAX 128
+  char_t text[UI_SETTINGS_DISCARD_TEXT_MAX];
+  errorChain(assetLocaleGetString(
+    &LOCALE.entry->data.locale,
+    "ui.confirm.discard_changes",
+    0,
+    text,
+    UI_SETTINGS_DISCARD_TEXT_MAX
+  ));
+  #undef UI_SETTINGS_DISCARD_TEXT_MAX
+
+  uiConfirmOpen(text, uiSettingsDiscardConfirmResult, def);
+
+  errorOk();
+}
+
+void uiSettingsDiscardConfirmResult(const bool_t result, void *user) {
+  uisettingstabdef_t *def = (uisettingstabdef_t *)user;
+
+  if(!result) {
+    uiMenuOpen(def->menu);
+    return;
+  }
+
+  def->load();
+}

archive/dusk/ui/frame/settings/uisettings.h

@@ -0,0 +1,135 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uimenu.h"
+#include "ui/frame/uiframe.h"
+#include "uisettingsdata.h"
+
+#define UI_SETTINGS_TAB_COUNT 4
+#define UI_SETTINGS_TAB_LABEL_MAX 32
+#define UI_SETTINGS_APPLY_LABEL_MAX 32
+
+typedef struct {
+  const char_t *localeId;
+  errorret_t (*init)(uisettingsdata_t *data);
+  uimenu_t *menu;
+  void (*load)(void);
+  void (*apply)(void);
+  bool_t (*hasChanges)(void);
+} uisettingstabdef_t;
+
+typedef struct {
+  uimenu_t tabsMenu;
+  uimenuitem_t tabs[UI_SETTINGS_TAB_COUNT];
+  char_t tabLabels[UI_SETTINGS_TAB_COUNT][UI_SETTINGS_TAB_LABEL_MAX];
+  char_t applyLabel[UI_SETTINGS_APPLY_LABEL_MAX];
+  uisettingsdata_t data;
+  uiframecache_t frameCache;
+} uisettings_t;
+
+extern uisettings_t UI_SETTINGS;
+extern uisettingstabdef_t UI_SETTINGS_TAB_DEFS[UI_SETTINGS_TAB_COUNT];
+
+/**
+ * Menu closed callback that flags a pending discard-changes
+ * confirmation if the menu's settings page/panel reports unsaved
+ * changes. Pass this directly as a settings page menu's closed
+ * callback. The pending def is picked up by uiSettingsUpdate on the
+ * next tick.
+ *
+ * @param menu The menu that was just closed.
+ */
+void uiSettingsDiscardMenuClosed(const uimenu_t *menu);
+
+/**
+ * Shows the discard-changes confirmation dialog for def. Called once
+ * by uiSettingsUpdate when uiSettingsDiscardMenuClosed has flagged a
+ * pending def.
+ *
+ * @param def The tab/panel def to show the confirmation for.
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsDiscardUpdate(uisettingstabdef_t *def);
+
+/**
+ * Callback passed to uiConfirmOpen by uiSettingsDiscardUpdate. Reopens
+ * the menu if the user chose to keep editing, otherwise reloads the
+ * widgets back to the actual engine values.
+ *
+ * @param result True if the user confirmed discarding changes, false
+ * to keep editing.
+ * @param user The uisettingstabdef_t* this confirmation belongs to.
+ */
+void uiSettingsDiscardConfirmResult(const bool_t result, void *user);
+
+/**
+ * Initializes the settings panel and all of its category pages.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsInit(void);
+
+/**
+ * Draws the settings panel. No-op when not visible.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsDraw(void);
+
+/**
+ * Updates the settings panel. Shows a discard-changes confirmation if
+ * the panel was just closed with unsaved changes.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsUpdate(void);
+
+/**
+ * Returns true when the settings panel is currently open.
+ *
+ * @returns True if open.
+ */
+bool_t uiSettingsIsOpen(void);
+
+/**
+ * Opens the settings panel. No-op when already open.
+ */
+void uiSettingsOpen();
+
+/**
+ * Closes the settings panel. No-op when already closed.
+ */
+void uiSettingsClose();
+
+/**
+ * Disposes of the settings panel.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsDispose(void);
+
+/**
+ * Loads every category page's widgets from the current engine settings.
+ * Called automatically by uiSettingsOpen.
+ */
+void uiSettingsLoad(void);
+
+/**
+ * Applies every category page's widget values to the engine settings.
+ * Called automatically when a page's own Apply button is pressed.
+ */
+void uiSettingsApply(void);
+
+/**
+ * Returns whether any category page has a widget value that differs
+ * from what was loaded.
+ *
+ * @returns True if there are unsaved changes.
+ */
+bool_t uiSettingsHasChanges(void);

archive/dusk/ui/frame/settings/uisettingsaudio.c

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uisettingsaudio.h"
+#include "uisettings.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+
+void uiSettingsAudioSelected(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  if(index != UI_SETTINGS_AUDIO_INDEX_APPLY) return;
+  uiSettingsAudioApply();
+}
+
+errorret_t uiSettingsAudioInit(uisettingsdata_t *data) {
+  uisettingsaudio_t *audio = &data->audio;
+  memoryZero(audio, sizeof(uisettingsaudio_t));
+
+  MENU_BEGIN(
+    &audio->menu, audio->items,
+    uiSettingsAudioSelected, uiSettingsDiscardMenuClosed, NULL
+  );
+  MENU_LABEL("No audio settings yet");
+  MENU_BUTTON(UI_SETTINGS.applyLabel);
+
+  MENU_END(audio->items, 1);
+
+  errorOk();
+}
+
+void uiSettingsAudioLoad(void) {
+}
+
+void uiSettingsAudioApply(void) {
+  uiMenuClose(&UI_SETTINGS.data.audio.menu);
+}
+
+bool_t uiSettingsAudioHasChanges(void) {
+  return false;
+}

archive/dusk/ui/frame/settings/uisettingsaudio.h

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "uisettingsdata.h"
+
+/**
+ * Initializes the audio settings page into the shared settings data
+ * union.
+ *
+ * @param data The shared settings data union to initialize into.
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsAudioInit(uisettingsdata_t *data);
+
+/**
+ * Loads the page's widgets from the current engine audio settings.
+ */
+void uiSettingsAudioLoad(void);
+
+/**
+ * Applies the page's widget values to the engine audio settings.
+ */
+void uiSettingsAudioApply(void);
+
+/**
+ * Returns whether any widget's value differs from what was loaded.
+ *
+ * @returns True if there are unsaved changes.
+ */
+bool_t uiSettingsAudioHasChanges(void);

archive/dusk/ui/frame/settings/uisettingsdata.h

@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uimenu.h"
+
+#define UI_SETTINGS_GENERAL_ITEM_COUNT 3
+#define UI_SETTINGS_GENERAL_INDEX_LANGUAGE 0
+#define UI_SETTINGS_GENERAL_INDEX_LANGUAGE_DETAIL 1
+#define UI_SETTINGS_GENERAL_INDEX_APPLY 2
+#define UI_SETTINGS_GENERAL_LOCALE_COUNT 3
+#define UI_SETTINGS_GENERAL_LABEL_MAX 32
+#define UI_SETTINGS_GENERAL_INFO_MAX 64
+
+typedef struct {
+  uimenu_t menu;
+  uimenuitem_t items[UI_SETTINGS_GENERAL_ITEM_COUNT];
+  const char_t *localeNames[UI_SETTINGS_GENERAL_LOCALE_COUNT];
+  char_t languageLabel[UI_SETTINGS_GENERAL_LABEL_MAX];
+  char_t labelInfo[UI_SETTINGS_GENERAL_INFO_MAX];
+} uisettingsgeneral_t;
+
+#define UI_SETTINGS_INPUT_ITEM_COUNT 2
+#define UI_SETTINGS_INPUT_LABEL_MAX 32
+#define UI_SETTINGS_INPUT_INDEX_DEADZONE 0
+#define UI_SETTINGS_INPUT_INDEX_APPLY 1
+
+typedef struct {
+  uimenu_t menu;
+  uimenuitem_t items[UI_SETTINGS_INPUT_ITEM_COUNT];
+  char_t deadzoneLabel[UI_SETTINGS_INPUT_LABEL_MAX];
+} uisettingsinput_t;
+
+#define UI_SETTINGS_DISPLAY_ITEM_COUNT 2
+#define UI_SETTINGS_DISPLAY_INDEX_APPLY 1
+
+typedef struct {
+  uimenu_t menu;
+  uimenuitem_t items[UI_SETTINGS_DISPLAY_ITEM_COUNT];
+} uisettingsdisplay_t;
+
+#define UI_SETTINGS_AUDIO_ITEM_COUNT 2
+#define UI_SETTINGS_AUDIO_INDEX_APPLY 1
+
+typedef struct {
+  uimenu_t menu;
+  uimenuitem_t items[UI_SETTINGS_AUDIO_ITEM_COUNT];
+} uisettingsaudio_t;
+
+/**
+ * Shared, overlapping storage for every settings tab's page data. Only
+ * one member is ever live at a time -- the active tab's Init writes
+ * into it, overwriting whatever the previously active tab left there.
+ * This trades simultaneous access to every tab for a memory footprint
+ * of only the single largest page.
+ */
+typedef union {
+  uisettingsgeneral_t general;
+  uisettingsinput_t input;
+  uisettingsdisplay_t display;
+  uisettingsaudio_t audio;
+} uisettingsdata_t;

archive/dusk/ui/frame/settings/uisettingsdisplay.c

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uisettingsdisplay.h"
+#include "uisettings.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+
+void uiSettingsDisplaySelected(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  if(index != UI_SETTINGS_DISPLAY_INDEX_APPLY) return;
+  uiSettingsDisplayApply();
+}
+
+errorret_t uiSettingsDisplayInit(uisettingsdata_t *data) {
+  uisettingsdisplay_t *display = &data->display;
+  memoryZero(display, sizeof(uisettingsdisplay_t));
+
+  MENU_BEGIN(
+    &display->menu, display->items,
+    uiSettingsDisplaySelected, uiSettingsDiscardMenuClosed, NULL
+  );
+  MENU_LABEL("No display settings yet");
+  MENU_BUTTON(UI_SETTINGS.applyLabel);
+
+  MENU_END(display->items, 1);
+
+  errorOk();
+}
+
+void uiSettingsDisplayLoad(void) {
+}
+
+void uiSettingsDisplayApply(void) {
+  uiMenuClose(&UI_SETTINGS.data.display.menu);
+}
+
+bool_t uiSettingsDisplayHasChanges(void) {
+  return false;
+}

archive/dusk/ui/frame/settings/uisettingsdisplay.h

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "uisettingsdata.h"
+
+/**
+ * Initializes the display settings page into the shared settings data
+ * union.
+ *
+ * @param data The shared settings data union to initialize into.
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsDisplayInit(uisettingsdata_t *data);
+
+/**
+ * Loads the page's widgets from the current engine display settings.
+ */
+void uiSettingsDisplayLoad(void);
+
+/**
+ * Applies the page's widget values to the engine display settings.
+ */
+void uiSettingsDisplayApply(void);
+
+/**
+ * Returns whether any widget's value differs from what was loaded.
+ *
+ * @returns True if there are unsaved changes.
+ */
+bool_t uiSettingsDisplayHasChanges(void);

archive/dusk/ui/frame/settings/uisettingsgeneral.c

@@ -0,0 +1,117 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uisettingsgeneral.h"
+#include "uisettings.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/string.h"
+#include "locale/localemanager.h"
+#include "locale/localeinfo.h"
+#include "asset/loader/locale/assetlocaleloader.h"
+
+static const localeinfo_t *const UI_SETTINGS_GENERAL_LOCALES[
+  UI_SETTINGS_GENERAL_LOCALE_COUNT
+] = {
+  &LOCALE_EN_US,
+  &LOCALE_JP_JP,
+  &LOCALE_ES_MX
+};
+
+void uiSettingsGeneralSelected(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  switch(index) {
+    case UI_SETTINGS_GENERAL_INDEX_APPLY:
+      uiSettingsGeneralApply();
+      break;
+
+    default:
+      break;
+  }
+}
+
+errorret_t uiSettingsGeneralInit(uisettingsdata_t *data) {
+  uisettingsgeneral_t *general = &data->general;
+  memoryZero(general, sizeof(uisettingsgeneral_t));
+
+  for(uint8_t i = 0; i < UI_SETTINGS_GENERAL_LOCALE_COUNT; i++) {
+    general->localeNames[i] = UI_SETTINGS_GENERAL_LOCALES[i]->name;
+  }
+
+  errorChain(assetLocaleGetString(
+    &LOCALE.entry->data.locale,
+    "ui.settings.general.language",
+    0,
+    general->languageLabel,
+    UI_SETTINGS_GENERAL_LABEL_MAX
+  ));
+  errorChain(assetLocaleGetString(
+    &LOCALE.entry->data.locale,
+    "ui.settings.general.language_detail",
+    0,
+    general->labelInfo,
+    UI_SETTINGS_GENERAL_INFO_MAX
+  ));
+
+  MENU_BEGIN(
+    &general->menu, general->items,
+    uiSettingsGeneralSelected, uiSettingsDiscardMenuClosed, NULL
+  );
+
+  MENU_DROPDOWN(
+    general->languageLabel, general->localeNames,
+    UI_SETTINGS_GENERAL_LOCALE_COUNT, 0
+  );
+  MENU_LABEL(general->labelInfo);
+
+  MENU_BUTTON(UI_SETTINGS.applyLabel);
+  MENU_END(general->items, 1);
+
+  errorOk();
+}
+
+void uiSettingsGeneralLoad(void) {
+  uisettingsgeneral_t *general = &UI_SETTINGS.data.general;
+
+  uint8_t index = 0;
+  for(uint8_t i = 0; i < UI_SETTINGS_GENERAL_LOCALE_COUNT; i++) {
+    if(stringCompare(LOCALE.locale->file, UI_SETTINGS_GENERAL_LOCALES[i]->file) != 0) {
+      continue;
+    }
+    index = i;
+    break;
+  }
+
+  uiDropdownSetSelectedIndex(
+    &general->items[UI_SETTINGS_GENERAL_INDEX_LANGUAGE].dropdown, index
+  );
+}
+
+void uiSettingsGeneralApply(void) {
+  uisettingsgeneral_t *general = &UI_SETTINGS.data.general;
+
+  uint8_t index = uiDropdownGetSelectedIndex(
+    &general->items[UI_SETTINGS_GENERAL_INDEX_LANGUAGE].dropdown
+  );
+  errorCatch(localeManagerSetLocale(UI_SETTINGS_GENERAL_LOCALES[index]));
+
+  uiMenuClose(&general->menu);
+}
+
+bool_t uiSettingsGeneralHasChanges(void) {
+  uisettingsgeneral_t *general = &UI_SETTINGS.data.general;
+
+  uint8_t index = uiDropdownGetSelectedIndex(
+    &general->items[UI_SETTINGS_GENERAL_INDEX_LANGUAGE].dropdown
+  );
+  return stringCompare(
+    LOCALE.locale->file, UI_SETTINGS_GENERAL_LOCALES[index]->file
+  ) != 0;
+}

archive/dusk/ui/frame/settings/uisettingsgeneral.h

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "uisettingsdata.h"
+
+/**
+ * Initializes the general settings page into the shared settings data
+ * union.
+ *
+ * @param data The shared settings data union to initialize into.
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsGeneralInit(uisettingsdata_t *data);
+
+/**
+ * Loads the page's widgets from the current engine general settings.
+ */
+void uiSettingsGeneralLoad(void);
+
+/**
+ * Applies the page's widget values to the engine general settings.
+ */
+void uiSettingsGeneralApply(void);
+
+/**
+ * Returns whether any widget's value differs from what was loaded.
+ *
+ * @returns True if there are unsaved changes.
+ */
+bool_t uiSettingsGeneralHasChanges(void);

archive/dusk/ui/frame/settings/uisettingsinput.c

@@ -0,0 +1,82 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uisettingsinput.h"
+#include "uisettings.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "locale/localemanager.h"
+#include "asset/loader/locale/assetlocaleloader.h"
+#include "input/input.h"
+#include "save/savesettings.h"
+
+void uiSettingsInputSelected(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  if(index != UI_SETTINGS_INPUT_INDEX_APPLY) return;
+  uiSettingsInputApply();
+}
+
+errorret_t uiSettingsInputInit(uisettingsdata_t *data) {
+  uisettingsinput_t *input = &data->input;
+  memoryZero(input, sizeof(uisettingsinput_t));
+
+  MENU_BEGIN(
+    &input->menu, input->items,
+    uiSettingsInputSelected, uiSettingsDiscardMenuClosed, NULL
+  );
+  #ifdef DUSK_INPUT_GAMEPAD
+    errorChain(assetLocaleGetString(
+      &LOCALE.entry->data.locale,
+      "ui.settings.input.deadzone",
+      0,
+      input->deadzoneLabel,
+      UI_SETTINGS_INPUT_LABEL_MAX
+    ));
+    MENU_SLIDER_FLOAT(
+      input->deadzoneLabel, INPUT_DEADZONE_DEFAULT, 0.0f, 1.0f, 0.05f
+    );
+  #else
+    MENU_LABEL("No input settings yet");
+  #endif
+
+  MENU_BUTTON(UI_SETTINGS.applyLabel);
+  MENU_END(input->items, 1);
+
+  errorOk();
+}
+
+void uiSettingsInputLoad(void) {
+  #ifdef DUSK_INPUT_GAMEPAD
+    uiSliderSetFloat(
+      &UI_SETTINGS.data.input.items[UI_SETTINGS_INPUT_INDEX_DEADZONE].slider,
+      INPUT.deadzone
+    );
+  #endif
+}
+
+void uiSettingsInputApply(void) {
+  #ifdef DUSK_INPUT_GAMEPAD
+    INPUT.deadzone = uiSliderGetFloat(
+      &UI_SETTINGS.data.input.items[UI_SETTINGS_INPUT_INDEX_DEADZONE].slider
+    );
+  #endif
+  errorCatch(errorPrint(saveSettingsWrite()));
+  uiMenuClose(&UI_SETTINGS.data.input.menu);
+}
+
+bool_t uiSettingsInputHasChanges(void) {
+  #ifdef DUSK_INPUT_GAMEPAD
+    if(uiSliderGetFloat(
+      &UI_SETTINGS.data.input.items[UI_SETTINGS_INPUT_INDEX_DEADZONE].slider
+    ) != INPUT.deadzone) return true;
+  #endif
+
+  return false;
+}

archive/dusk/ui/frame/settings/uisettingsinput.h

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "uisettingsdata.h"
+
+/**
+ * Initializes the input settings page into the shared settings data
+ * union.
+ *
+ * @param data The shared settings data union to initialize into.
+ * @return Any error that occurs.
+ */
+errorret_t uiSettingsInputInit(uisettingsdata_t *data);
+
+/**
+ * Loads the page's widgets from the current engine input settings.
+ */
+void uiSettingsInputLoad(void);
+
+/**
+ * Applies the page's widget values to the engine input settings.
+ */
+void uiSettingsInputApply(void);
+
+/**
+ * Returns whether any widget's value differs from what was loaded.
+ *
+ * @returns True if there are unsaved changes.
+ */
+bool_t uiSettingsInputHasChanges(void);

archive/dusk/ui/frame/uiconfirm.c

@@ -0,0 +1,126 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiconfirm.h"
+#include "uiframe.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/math.h"
+#include "display/screen/screen.h"
+#include "display/text/text.h"
+#include "display/color.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/texture/texture.h"
+#include "display/shader/shaderunlit.h"
+
+#define UI_CONFIRM_BACKDROP_COLOR color4b(0, 0, 0, 160)
+
+uiconfirm_t UI_CONFIRM;
+
+void uiConfirmSelected(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+) {
+  UI_CONFIRM.result = index == UI_CONFIRM_INDEX_CONFIRM;
+  uiConfirmClose();
+}
+
+void uiConfirmClosed(const uimenu_t *menu) {
+  if(UI_CONFIRM.callback != NULL) {
+    UI_CONFIRM.callback(UI_CONFIRM.result, UI_CONFIRM.user);
+  }
+}
+
+errorret_t uiConfirmInit(void) {
+  memoryZero(&UI_CONFIRM, sizeof(uiconfirm_t));
+  uiLabelInit(&UI_CONFIRM.textLabel, &FONT_DEFAULT);
+
+  MENU_BEGIN(
+    &UI_CONFIRM.menu, UI_CONFIRM.items, uiConfirmSelected, uiConfirmClosed, NULL
+  );
+  MENU_BUTTON("Confirm");
+  MENU_BUTTON("Cancel");
+
+  MENU_END(UI_CONFIRM.items, menuIndex);
+
+  errorOk();
+}
+
+errorret_t uiConfirmDraw(void) {
+  if(!uiMenuIsActive(&UI_CONFIRM.menu)) errorOk();
+
+  spritebatchsprite_t backdropSprite = {
+    .min = { 0.0f, 0.0f, 0.0f },
+    .max = { (float_t)SCREEN.width, (float_t)SCREEN.height, 0.0f },
+    .uvMin = { 0.0f, 0.0f },
+    .uvMax = { 1.0f, 1.0f }
+  };
+  shadermaterial_t backdropMaterial = {
+    .unlit = {
+      .color = UI_CONFIRM_BACKDROP_COLOR,
+      .texture = &TEXTURE_WHITE
+    }
+  };
+  errorChain(
+    spriteBatchBuffer(&backdropSprite, 1, &SHADER_UNLIT, backdropMaterial)
+  );
+
+  int32_t textW, textH;
+  uiLabelGetSize(&UI_CONFIRM.textLabel, &textW, &textH);
+
+  float_t rowHeight = (float_t)FONT_DEFAULT.tileset->tileHeight;
+  float_t width = mathMax(
+    (float_t)textW + (UI_FRAME_START_X * 2), UI_CONFIRM_MIN_WIDTH
+  );
+  float_t height = (UI_FRAME_START_Y * 2) + rowHeight + UI_FRAME_PADDING_Y +
+    rowHeight;
+  float_t x = (float_t)SCREEN.scanX + ((float_t)SCREEN.scanWidth - width) * 0.5f;
+  float_t y = (float_t)SCREEN.scanY + ((float_t)SCREEN.scanHeight - height) * 0.5f;
+
+  errorChain(uiFrameDrawCached(&UI_CONFIRM.frameCache, x, y, width, height));
+
+  float_t contentX = x + UI_FRAME_START_X;
+  float_t contentY = y + UI_FRAME_START_Y;
+  float_t contentWidth = width - (UI_FRAME_START_X * 2);
+
+  errorChain(uiLabelDraw(&UI_CONFIRM.textLabel, contentX, contentY));
+
+  float_t buttonsY = contentY + rowHeight + UI_FRAME_PADDING_Y;
+  errorChain(uiMenuDraw(&UI_CONFIRM.menu, contentX, buttonsY, contentWidth, rowHeight));
+
+  errorOk();
+}
+
+bool_t uiConfirmIsOpen(void) {
+  return uiMenuIsActive(&UI_CONFIRM.menu);
+}
+
+bool_t uiConfirmGetResult(void) {
+  return UI_CONFIRM.result;
+}
+
+void uiConfirmOpen(
+  const char_t *question,
+  uiconfirmcallback_t callback,
+  void *user
+) {
+  assertNotNull(question, "Question cannot be NULL");
+  uiLabelSetText(&UI_CONFIRM.textLabel, question);
+  UI_CONFIRM.callback = callback;
+  UI_CONFIRM.user = user;
+  UI_CONFIRM.result = false;
+  uiMenuOpen(&UI_CONFIRM.menu);
+}
+
+void uiConfirmClose(void) {
+  uiMenuClose(&UI_CONFIRM.menu);
+}
+
+errorret_t uiConfirmDispose(void) {
+  errorOk();
+}

archive/dusk/ui/frame/uiconfirm.h

@@ -0,0 +1,96 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uimenu.h"
+#include "ui/widget/uilabel.h"
+#include "ui/frame/uiframe.h"
+
+#define UI_CONFIRM_MIN_WIDTH 160.0f
+#define UI_CONFIRM_INDEX_CONFIRM 0
+#define UI_CONFIRM_INDEX_CANCEL 1
+#define UI_CONFIRM_ITEM_COUNT 2
+
+/**
+ * Callback invoked once a confirm dialog is dismissed.
+ *
+ * @param result True if Confirm was selected, false if Cancel was
+ * selected or the dialog was backed out of.
+ * @param user Arbitrary pointer passed to uiConfirmOpen.
+ */
+typedef void (*uiconfirmcallback_t)(const bool_t result, void *user);
+
+typedef struct {
+  uilabel_t textLabel;
+  uimenu_t menu;
+  uimenuitem_t items[UI_CONFIRM_ITEM_COUNT];
+  uiconfirmcallback_t callback;
+  void *user;
+  bool_t result;
+  uiframecache_t frameCache;
+} uiconfirm_t;
+
+extern uiconfirm_t UI_CONFIRM;
+
+/**
+ * Initializes the confirm dialog.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiConfirmInit(void);
+
+/**
+ * Draws the confirm dialog: a semi-transparent black backdrop covering
+ * the whole screen, then its own centered frame with the question text
+ * and Confirm/Cancel buttons. No-op when not open.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiConfirmDraw(void);
+
+/**
+ * Returns true when the confirm dialog is currently open.
+ *
+ * @returns True if open.
+ */
+bool_t uiConfirmIsOpen(void);
+
+/**
+ * Returns the result of the most recently dismissed confirm dialog.
+ *
+ * @returns True if Confirm was selected, false otherwise.
+ */
+bool_t uiConfirmGetResult(void);
+
+/**
+ * Opens the confirm dialog with the given question text. callback is
+ * invoked exactly once with the result, whether the dialog was
+ * dismissed by selecting a button or by pressing cancel/back.
+ *
+ * @param question Display text; copied internally, safe to be transient.
+ * @param callback Called with the result once the dialog closes. May be
+ * NULL.
+ * @param user Arbitrary pointer passed through to callback.
+ */
+void uiConfirmOpen(
+  const char_t *question,
+  uiconfirmcallback_t callback,
+  void *user
+);
+
+/**
+ * Closes the confirm dialog. No-op when already closed.
+ */
+void uiConfirmClose(void);
+
+/**
+ * Disposes of the confirm dialog.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiConfirmDispose(void);

archive/dusk/ui/frame/uiframe.c

@@ -0,0 +1,161 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiframe.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "display/texture/texture.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+#include "display/color.h"
+
+uiframe_t UI_FRAME;
+
+errorret_t uiFrameInit(void) {
+  memoryZero(&UI_FRAME, sizeof(uiframe_t));
+  
+  // Init texture.
+  color_t border = color4b(0, 50, 255, 255);
+  color_t center = color4b(0, 100, 220, 240);
+
+  for(uint8_t y = 0; y < UI_FRAME_TEXTURE_HEIGHT_POW2; y++) {
+    for(uint8_t x = 0; x < UI_FRAME_TEXTURE_WIDTH_POW2; x++) {
+      color_t c;
+      if(x >= UI_FRAME_TEXTURE_WIDTH || y >= UI_FRAME_TEXTURE_HEIGHT) {
+        c = COLOR_TRANSPARENT;
+      } else if(
+        y < UI_FRAME_TILE_HEIGHT || y >= UI_FRAME_TILE_HEIGHT * 2 ||
+        x < UI_FRAME_TILE_WIDTH  || x >= UI_FRAME_TILE_WIDTH * 2
+      ) {
+        c = border;
+      } else {
+        c = center;
+      }
+      UI_FRAME.pixels[y * UI_FRAME_TEXTURE_WIDTH_POW2 + x] = c;
+    }
+  }
+
+  errorChain(textureInit(
+    &UI_FRAME.texture,
+    UI_FRAME_TEXTURE_WIDTH_POW2, UI_FRAME_TEXTURE_HEIGHT_POW2,
+    TEXTURE_FORMAT_RGBA,
+    (texturedata_t){ .rgbaColors = UI_FRAME.pixels }
+  ));
+
+  UI_FRAME.tileset.tileWidth = UI_FRAME_TILE_WIDTH;
+  UI_FRAME.tileset.tileHeight = UI_FRAME_TILE_HEIGHT;
+  UI_FRAME.tileset.columns = 3;
+  UI_FRAME.tileset.rows = 3;
+  UI_FRAME.tileset.tileCount = 9;
+  UI_FRAME.tileset.uv[0] =
+    (float_t)UI_FRAME_TILE_WIDTH / UI_FRAME_TEXTURE_WIDTH_POW2;
+  UI_FRAME.tileset.uv[1] =
+    (float_t)UI_FRAME_TILE_HEIGHT / UI_FRAME_TEXTURE_HEIGHT_POW2;
+
+  errorOk();
+}
+
+errorret_t uiFrameDraw(
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+) {
+  shadermaterial_t material = {
+    .unlit = {
+      .color = COLOR_WHITE,
+      .texture = &UI_FRAME.texture
+    }
+  };
+  spritebatchsprite_t sprites[9];
+  uiFrameBuildSprites(sprites, x, y, width, height);
+  return spriteBatchBuffer(sprites, 9, &SHADER_UNLIT, material);
+}
+
+void uiFrameBuildSprites(
+  spritebatchsprite_t sprites[9],
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+) {
+  float_t tileW = (float_t)UI_FRAME_BORDER_WIDTH;
+  float_t tileH = (float_t)UI_FRAME_BORDER_HEIGHT;
+
+  sprites[0] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 0, 0,
+    x, y, tileW, tileH
+  );
+  sprites[1] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 1, 0,
+    x + tileW, y, width - (tileW * 2.0f), tileH
+  );
+  sprites[2] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 2, 0,
+    x + width - tileW, y, tileW, tileH
+  );
+  sprites[3] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 0, 1,
+    x, y + tileH, tileW, height - (tileH * 2.0f)
+  );
+  sprites[4] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 1, 1,
+    x + tileW, y + tileH,
+    width - (tileW * 2.0f), height - (tileH * 2.0f)
+  );
+  sprites[5] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 2, 1,
+    x + width - tileW, y + tileH, tileW, height - (tileH * 2.0f)
+  );
+  sprites[6] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 0, 2,
+    x, y + height - tileH, tileW, tileH
+  );
+  sprites[7] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 1, 2,
+    x + tileW, y + height - tileH, width - (tileW * 2.0f), tileH
+  );
+  sprites[8] = spriteBatchSpriteTilesetPosition(
+    &UI_FRAME.tileset, 2, 2,
+    x + width - tileW, y + height - tileH, tileW, tileH
+  );
+}
+
+errorret_t uiFrameDrawCached(
+  uiframecache_t *cache,
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+) {
+  assertNotNull(cache, "Frame cache cannot be NULL");
+
+  if(
+    !cache->built ||
+    cache->lastX != x || cache->lastY != y ||
+    cache->lastWidth != width || cache->lastHeight != height
+  ) {
+    uiFrameBuildSprites(cache->sprites, x, y, width, height);
+    cache->lastX = x;
+    cache->lastY = y;
+    cache->lastWidth = width;
+    cache->lastHeight = height;
+    cache->built = true;
+  }
+
+  shadermaterial_t material = {
+    .unlit = {
+      .color = COLOR_WHITE,
+      .texture = &UI_FRAME.texture
+    }
+  };
+  return spriteBatchBuffer(cache->sprites, 9, &SHADER_UNLIT, material);
+}
+
+errorret_t uiFrameDispose(void) {
+  return textureDispose(&UI_FRAME.texture);
+}

archive/dusk/ui/frame/uiframe.h

@@ -0,0 +1,122 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/texture/texture.h"
+#include "display/texture/tileset.h"
+#include "display/spritebatch/spritebatchsprite.h"
+
+#define UI_FRAME_BORDER_WIDTH 6
+#define UI_FRAME_BORDER_HEIGHT 6
+#define UI_FRAME_PADDING_X 2
+#define UI_FRAME_PADDING_Y 2
+#define UI_FRAME_START_X (UI_FRAME_BORDER_WIDTH + UI_FRAME_PADDING_X)
+#define UI_FRAME_START_Y (UI_FRAME_BORDER_HEIGHT + UI_FRAME_PADDING_Y)
+#define UI_FRAME_TILE_WIDTH 1
+#define UI_FRAME_TILE_HEIGHT 1
+#define UI_FRAME_TEXTURE_WIDTH (UI_FRAME_TILE_WIDTH * 3)
+#define UI_FRAME_TEXTURE_HEIGHT (UI_FRAME_TILE_HEIGHT * 3)
+#define UI_FRAME_TEXTURE_WIDTH_POW2 4
+#define UI_FRAME_TEXTURE_HEIGHT_POW2 4 
+
+typedef struct {
+  tileset_t tileset;
+  texture_t texture;
+  color_t pixels[UI_FRAME_BORDER_WIDTH * UI_FRAME_BORDER_HEIGHT];
+} uiframe_t;
+
+extern uiframe_t UI_FRAME;
+
+/**
+ * Initializes the global UI_FRAME: builds the dummy texture and
+ * configures the tileset. Call once after displayInit().
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFrameInit(void);
+
+/**
+ * Draws UI_FRAME using 9-slice rendering from its 3x3 tileset.
+ * Pushes quads to the sprite batch without flushing.
+ *
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @param width Total width of the frame.
+ * @param height Total height of the frame.
+ * @return Any error that occurs.
+ */
+errorret_t uiFrameDraw(
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+);
+
+/**
+ * Builds the 9 sprites for a 9-slice frame at the given rect. Used
+ * internally by uiFrameDraw and uiFrameDrawCached -- call directly only
+ * if you need the raw sprites instead of buffering them.
+ *
+ * @param sprites Destination array of exactly 9 sprites.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @param width Total width of the frame.
+ * @param height Total height of the frame.
+ */
+void uiFrameBuildSprites(
+  spritebatchsprite_t sprites[9],
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+);
+
+/**
+ * A frame's cached 9-slice sprites, plus the rect they were built for.
+ * Owned by whichever widget/screen draws a frame repeatedly (dialogs,
+ * textboxes, settings panels) so uiFrameDrawCached can skip rebuilding
+ * the sprites when the rect hasn't moved since the last draw.
+ */
+typedef struct {
+  spritebatchsprite_t sprites[9];
+  bool_t built;
+  float_t lastX;
+  float_t lastY;
+  float_t lastWidth;
+  float_t lastHeight;
+} uiframecache_t;
+
+/**
+ * Draws a 9-slice frame using a caller-owned cache, only rebuilding the
+ * sprites (via uiFrameBuildSprites) when x/y/width/height differ from
+ * the last call -- unlike uiFrameDraw, which rebuilds unconditionally
+ * every time. Prefer this for frames redrawn every frame at a fixed or
+ * rarely-changing rect (dialogs, panels); use plain uiFrameDraw for
+ * genuinely one-off or per-frame-varying rects.
+ *
+ * @param cache Caller-owned cache, zero-initialized before first use.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @param width Total width of the frame.
+ * @param height Total height of the frame.
+ * @return Any error that occurs.
+ */
+errorret_t uiFrameDrawCached(
+  uiframecache_t *cache,
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+);
+
+/**
+ * Disposes of the global UI_FRAME, releasing its GPU texture.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFrameDispose(void);

archive/dusk/ui/overlay/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uicrop.c
+    uifullbox.c
+    uiloading.c
+)

archive/dusk/ui/overlay/uicrop.c

@@ -0,0 +1,89 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uicrop.h"
+#include "display/screen/screen.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+#include "display/texture/texture.h"
+
+uicrop_t UI_CROP;
+
+errorret_t uiCropInit(void) {
+  UI_CROP.color = COLOR_BLACK;
+  errorOk();
+}
+
+errorret_t uiCropDraw(void) {
+  #ifndef DUSK_DISPLAY_SIZE_DYNAMIC
+    errorOk();
+  #endif
+
+  if(
+    SCREEN.scanX == 0 &&
+    SCREEN.scanY == 0 &&
+    SCREEN.scanWidth == SCREEN.width &&
+    SCREEN.scanHeight == SCREEN.height
+  ) errorOk();
+
+  float_t x0 = (float_t)SCREEN.scanX;
+  float_t y0 = (float_t)SCREEN.scanY;
+  float_t x1 = (float_t)(SCREEN.scanX + SCREEN.scanWidth);
+  float_t y1 = (float_t)(SCREEN.scanY + SCREEN.scanHeight);
+  float_t w = (float_t)SCREEN.width;
+  float_t h = (float_t)SCREEN.height;
+
+  spritebatchsprite_t sprites[4];
+  int32_t count = 0;
+
+  if(SCREEN.scanX > 0) {
+    sprites[count++] = (spritebatchsprite_t){
+      .min = { 0.0f, 0.0f, 0.0f },
+      .max = { x0, h, 0.0f },
+      .uvMin = { 0.0f, 0.0f },
+      .uvMax = { 1.0f, 1.0f }
+    };
+  }
+
+  if(SCREEN.scanX + SCREEN.scanWidth < SCREEN.width) {
+    sprites[count++] = (spritebatchsprite_t){
+      .min = { x1, 0.0f, 0.0f },
+      .max = { w, h, 0.0f },
+      .uvMin = { 0.0f, 0.0f },
+      .uvMax = { 1.0f, 1.0f }
+    };
+  }
+
+  if(SCREEN.scanY > 0) {
+    sprites[count++] = (spritebatchsprite_t){
+      .min = { x0, 0.0f, 0.0f },
+      .max = { x1, y0, 0.0f },
+      .uvMin = { 0.0f, 0.0f },
+      .uvMax = { 1.0f, 1.0f }
+    };
+  }
+
+  if(SCREEN.scanY + SCREEN.scanHeight < SCREEN.height) {
+    sprites[count++] = (spritebatchsprite_t){
+      .min = { x0, y1, 0.0f },
+      .max = { x1, h, 0.0f },
+      .uvMin = { 0.0f, 0.0f },
+      .uvMax = { 1.0f, 1.0f }
+    };
+  }
+
+  if(count == 0) errorOk();
+
+  shadermaterial_t material = {
+    .unlit = {
+      .color = UI_CROP.color,
+      .texture = &TEXTURE_WHITE
+    }
+  };
+  errorChain(spriteBatchBuffer(sprites, count, &SHADER_UNLIT, material));
+  errorOk();
+}

archive/dusk/ui/overlay/uicrop.h

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/color.h"
+
+typedef struct {
+  color_t color;
+} uicrop_t;
+
+extern uicrop_t UI_CROP;
+
+/**
+ * Initializes the crop bars to opaque black.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiCropInit(void);
+
+/**
+ * Renders solid-color bars covering every area outside the
+ * current scan-safe region. No-ops when the scan area equals
+ * the full viewport.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiCropDraw(void);

archive/dusk/ui/overlay/uifullbox.c

@@ -0,0 +1,122 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uifullbox.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "time/time.h"
+#include "display/screen/screen.h"
+#include "display/texture/texture.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+
+uifullbox_t UI_FULLBOX_UNDER;
+uifullbox_t UI_FULLBOX_OVER;
+
+void uiFullboxInit(uifullbox_t *fullbox) {
+  assertNotNull(fullbox, "fullbox must not be NULL");
+  memoryZero(fullbox, sizeof(uifullbox_t));
+  eventInit(
+    &fullbox->onTransitionEnd,
+    fullbox->onTransitionEndCallbacks,
+    fullbox->onTransitionEndUsers,
+    4
+  );
+}
+
+void uiFullboxUpdate(uifullbox_t *fullbox, float_t delta) {
+  assertNotNull(fullbox, "fullbox must not be NULL");
+  if(fullbox->duration <= 0.0f || fullbox->time >= fullbox->duration) return;
+
+  fullbox->time += delta;
+  if(fullbox->time >= fullbox->duration) {
+    fullbox->time = fullbox->duration;
+    eventInvoke(&fullbox->onTransitionEnd, fullbox);
+  }
+}
+
+static color_t uiFullboxGetColor(const uifullbox_t *fullbox) {
+  if(fullbox->duration <= 0.0f || fullbox->time >= fullbox->duration) {
+    return fullbox->toColor;
+  }
+  float_t t = easingApply(fullbox->easing, fullbox->time / fullbox->duration);
+  return color4b(
+    (uint8_t)((float_t)fullbox->fromColor.r +
+      ((float_t)fullbox->toColor.r - (float_t)fullbox->fromColor.r) * t),
+    (uint8_t)((float_t)fullbox->fromColor.g +
+      ((float_t)fullbox->toColor.g - (float_t)fullbox->fromColor.g) * t),
+    (uint8_t)((float_t)fullbox->fromColor.b +
+      ((float_t)fullbox->toColor.b - (float_t)fullbox->fromColor.b) * t),
+    (uint8_t)((float_t)fullbox->fromColor.a +
+      ((float_t)fullbox->toColor.a - (float_t)fullbox->fromColor.a) * t)
+  );
+}
+
+errorret_t uiFullboxDraw(uifullbox_t *fullbox) {
+  assertNotNull(fullbox, "fullbox must not be NULL");
+
+  color_t color = uiFullboxGetColor(fullbox);
+  if(color.a == 0) errorOk();
+
+  spritebatchsprite_t sprite = {
+    .min = { 0.0f, 0.0f, 0.0f },
+    .max = { (float_t)SCREEN.width, (float_t)SCREEN.height, 0.0f },
+    .uvMin = { 0.0f, 0.0f },
+    .uvMax = { 1.0f, 1.0f }
+  };
+  shadermaterial_t material = {
+    .unlit = {
+      .color = color,
+      .texture = &TEXTURE_WHITE
+    }
+  };
+  errorChain(spriteBatchBuffer(&sprite, 1, &SHADER_UNLIT, material));
+  errorOk();
+}
+
+void uiFullboxTransition(
+  uifullbox_t *fullbox,
+  color_t from,
+  color_t to,
+  float_t duration,
+  easingtype_t easing
+) {
+  assertNotNull(fullbox, "fullbox must not be NULL");
+  fullbox->fromColor = from;
+  fullbox->toColor = to;
+  fullbox->duration = duration;
+  fullbox->time = 0.0f;
+  fullbox->easing = easing;
+}
+
+errorret_t uiFullboxUnderInit(void) {
+  uiFullboxInit(&UI_FULLBOX_UNDER);
+  errorOk();
+}
+
+errorret_t uiFullboxUnderUpdate(void) {
+  uiFullboxUpdate(&UI_FULLBOX_UNDER, TIME.delta);
+  errorOk();
+}
+
+errorret_t uiFullboxUnderDraw(void) {
+  return uiFullboxDraw(&UI_FULLBOX_UNDER);
+}
+
+errorret_t uiFullboxOverInit(void) {
+  uiFullboxInit(&UI_FULLBOX_OVER);
+  errorOk();
+}
+
+errorret_t uiFullboxOverUpdate(void) {
+  uiFullboxUpdate(&UI_FULLBOX_OVER, TIME.delta);
+  errorOk();
+}
+
+errorret_t uiFullboxOverDraw(void) {
+  return uiFullboxDraw(&UI_FULLBOX_OVER);
+}

archive/dusk/ui/overlay/uifullbox.h

@@ -0,0 +1,109 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/color.h"
+#include "animation/easing.h"
+#include "event/event.h"
+
+typedef struct {
+  color_t fromColor;
+  color_t toColor;
+  float_t duration;
+  float_t time;
+  easingtype_t easing;
+  eventcallback_t onTransitionEndCallbacks[4];
+  void *onTransitionEndUsers[4];
+  event_t onTransitionEnd;
+} uifullbox_t;
+
+extern uifullbox_t UI_FULLBOX_UNDER;
+extern uifullbox_t UI_FULLBOX_OVER;
+
+/**
+ * Initializes a fullbox, zeroing all fields.
+ *
+ * @param fullbox The fullbox to initialize.
+ */
+void uiFullboxInit(uifullbox_t *fullbox);
+
+/**
+ * Advances the fullbox transition. Fires onTransitionEnd once when the
+ * transition completes. Safe to call when no transition is running.
+ *
+ * @param fullbox The fullbox to update.
+ * @param delta   Seconds elapsed since last update.
+ */
+void uiFullboxUpdate(uifullbox_t *fullbox, float_t delta);
+
+/**
+ * Renders the fullbox. Skipped entirely when the current alpha is zero.
+ *
+ * @param fullbox The fullbox to draw.
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxDraw(uifullbox_t *fullbox);
+
+/**
+ * Begins a color transition.
+ *
+ * @param fullbox  The fullbox to transition.
+ * @param from     Start color.
+ * @param to       End color.
+ * @param duration Transition duration in seconds.
+ * @param easing   Easing function to apply.
+ */
+void uiFullboxTransition(
+  uifullbox_t *fullbox,
+  color_t from,
+  color_t to,
+  float_t duration,
+  easingtype_t easing
+);
+
+/**
+ * Init function for UI_FULLBOX_UNDER (registered in UI_ELEMENTS).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxUnderInit(void);
+
+/**
+ * Update function for UI_FULLBOX_UNDER (registered in UI_ELEMENTS).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxUnderUpdate(void);
+
+/**
+ * Draw function for UI_FULLBOX_UNDER (registered in UI_ELEMENTS).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxUnderDraw(void);
+
+/**
+ * Init function for UI_FULLBOX_OVER (registered in UI_ELEMENTS).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxOverInit(void);
+
+/**
+ * Update function for UI_FULLBOX_OVER (registered in UI_ELEMENTS).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxOverUpdate(void);
+
+/**
+ * Draw function for UI_FULLBOX_OVER (registered in UI_ELEMENTS).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiFullboxOverDraw(void);

archive/dusk/ui/overlay/uiloading.c

@@ -0,0 +1,111 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiloading.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "time/time.h"
+#include "display/text/text.h"
+#include "display/screen/screen.h"
+#include "uifullbox.h"
+
+#define UI_LOADING_TEXT "loading"
+
+uiloading_t UI_LOADING;
+
+errorret_t uiLoadingInit(void) {
+  memoryZero(&UI_LOADING, sizeof(uiloading_t));
+  uiLabelInit(&UI_LOADING.textLabel, &FONT_DEFAULT);
+  uiLabelSetText(&UI_LOADING.textLabel, UI_LOADING_TEXT);
+  eventInit(
+    &UI_LOADING.onTransitionEnd,
+    UI_LOADING.onTransitionEndCallbacks,
+    UI_LOADING.onTransitionEndUsers,
+    4
+  );
+  errorOk();
+}
+
+errorret_t uiLoadingUpdate(void) {
+  if(UI_LOADING.duration > 0.0f && UI_LOADING.time < UI_LOADING.duration) {
+    UI_LOADING.time += TIME.delta;
+    if(UI_LOADING.time >= UI_LOADING.duration) {
+      UI_LOADING.time = UI_LOADING.duration;
+      eventInvoke(&UI_LOADING.onTransitionEnd, &UI_LOADING);
+    }
+  }
+  errorOk();
+}
+
+errorret_t uiLoadingDraw(void) {
+  float_t alpha;
+  if(UI_LOADING.duration <= 0.0f || UI_LOADING.time >= UI_LOADING.duration) {
+    alpha = UI_LOADING.toAlpha;
+  } else {
+    float_t t = UI_LOADING.time / UI_LOADING.duration;
+    alpha = UI_LOADING.fromAlpha +
+      (UI_LOADING.toAlpha - UI_LOADING.fromAlpha) * t;
+  }
+
+  if(alpha <= 0.0f) errorOk();
+
+  int32_t textW, textH;
+  uiLabelGetSize(&UI_LOADING.textLabel, &textW, &textH);
+
+  float_t x = (float_t)(SCREEN.scanX + SCREEN.scanWidth) -
+    (float_t)textW - UI_LOADING_MARGIN;
+  float_t y = (float_t)(SCREEN.scanY + SCREEN.scanHeight) -
+    (float_t)textH - UI_LOADING_MARGIN;
+
+  color_t color = COLOR_WHITE;
+  color.a = (uint8_t)(alpha * 255.0f);
+  uiLabelSetColor(&UI_LOADING.textLabel, color);
+
+  errorChain(uiLabelDraw(&UI_LOADING.textLabel, x, y));
+  errorOk();
+}
+
+static void uiLoadingTransition(
+  const float_t from,
+  const float_t to,
+  const eventcallback_t callback,
+  void *user
+) {
+  UI_LOADING.fromAlpha = from;
+  UI_LOADING.toAlpha = to;
+  UI_LOADING.duration = UI_LOADING_FADE_DURATION;
+  UI_LOADING.time = 0.0f;
+  eventInit(
+    &UI_LOADING.onTransitionEnd,
+    UI_LOADING.onTransitionEndCallbacks,
+    UI_LOADING.onTransitionEndUsers,
+    4
+  );
+  if(callback) eventSubscribe(&UI_LOADING.onTransitionEnd, callback, user);
+}
+
+void uiLoadingShow(eventcallback_t callback, void *user) {
+  uiLoadingTransition(0.0f, 1.0f, callback, user);
+  uiFullboxTransition(
+    &UI_FULLBOX_OVER,
+    COLOR_TRANSPARENT_BLACK,
+    COLOR_BLACK,
+    UI_LOADING_FADE_DURATION,
+    EASING_LINEAR
+  );
+}
+
+void uiLoadingHide(eventcallback_t callback, void *user) {
+  uiLoadingTransition(1.0f, 0.0f, callback, user);
+  uiFullboxTransition(
+    &UI_FULLBOX_OVER,
+    COLOR_BLACK,
+    COLOR_TRANSPARENT_BLACK,
+    UI_LOADING_FADE_DURATION,
+    EASING_LINEAR
+  );
+}

archive/dusk/ui/overlay/uiloading.h

@@ -0,0 +1,65 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "event/event.h"
+#include "ui/widget/uilabel.h"
+
+#define UI_LOADING_FADE_DURATION 0.5f
+#define UI_LOADING_MARGIN 8.0f
+
+typedef struct {
+  float_t fromAlpha;
+  float_t toAlpha;
+  float_t duration;
+  float_t time;
+  eventcallback_t onTransitionEndCallbacks[4];
+  void *onTransitionEndUsers[4];
+  event_t onTransitionEnd;
+  uilabel_t textLabel;
+} uiloading_t;
+
+extern uiloading_t UI_LOADING;
+
+/**
+ * Initializes the loading indicator.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiLoadingInit(void);
+
+/**
+ * Advances the loading indicator fade transition. Fires onTransitionEnd once
+ * when the transition completes.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiLoadingUpdate(void);
+
+/**
+ * Draws the loading indicator. No-op when fully transparent.
+ *
+ * @return Error state.
+ */
+errorret_t uiLoadingDraw(void);
+
+/**
+ * Fades the loading indicator in. Invokes callback when fully visible.
+ *
+ * @param callback Called when the fade-in completes. May be NULL.
+ * @param user     Forwarded to the callback unchanged.
+ */
+void uiLoadingShow(eventcallback_t callback, void *user);
+
+/**
+ * Fades the loading indicator out. Invokes callback when fully hidden.
+ *
+ * @param callback Called when the fade-out completes. May be NULL.
+ * @param user     Forwarded to the callback unchanged.
+ */
+void uiLoadingHide(eventcallback_t callback, void *user);

archive/dusk/ui/transition/CMakeLists.txt

@@ -0,0 +1,10 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uitransition.c
+    uitransitionfade.c
+)

archive/dusk/ui/transition/uitransition.c

@@ -0,0 +1,81 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uitransition.h"
+#include "uitransitionfade.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "time/time.h"
+#include "util/math.h"
+
+uitransition_t UI_TRANSITION;
+
+uitransitiondrawfunc_t UI_TRANSITION_TYPE_DRAW[UI_TRANSITION_TYPE_COUNT] = {
+  [UI_TRANSITION_TYPE_FADE] = uiTransitionFadeDraw
+};
+
+errorret_t uiTransitionInit(void) {
+  memoryZero(&UI_TRANSITION, sizeof(uitransition_t));
+
+  // uiTransitionStart((uitransitionstartparams_t){
+  //   .duration = 5.0f,
+  //   .type = UI_TRANSITION_TYPE_FADE,
+  //   .params = {
+  //     .fade = {
+  //       .easing = EASING_OUT_QUART,
+  //       .fromColor = COLOR_TRANSPARENT_BLACK,
+  //       .toColor = COLOR_BLACK
+  //     }
+  //   },
+  //   .finished = NULL,
+  //   .user = NULL
+  // });
+
+  errorOk();
+}
+
+errorret_t uiTransitionUpdate(void) {
+  // Update time.
+  float_t newTime = UI_TRANSITION.data.time + TIME.delta;
+
+  UI_TRANSITION.data.time = mathClamp(
+    newTime,
+    0.0f,
+    UI_TRANSITION.data.duration
+  );
+  UI_TRANSITION.data.t = (
+    (UI_TRANSITION.data.duration <= 0.0f) ?
+    1.0f :
+    (UI_TRANSITION.data.time / UI_TRANSITION.data.duration)
+  );
+
+  if(UI_TRANSITION.data.t >= 1.0f && UI_TRANSITION.finished) {
+    UI_TRANSITION.finished(UI_TRANSITION.user);
+  }
+
+  errorOk();
+}
+
+errorret_t uiTransitionDraw(void) {
+  uitransitiondrawfunc_t draw = UI_TRANSITION_TYPE_DRAW[UI_TRANSITION.type];
+  if(!draw) errorOk();
+  return draw(&UI_TRANSITION.data);
+}
+
+void uiTransitionStart(const uitransitionstartparams_t info) {
+  assertTrue(info.type > UI_TRANSITION_TYPE_NULL, "Invalid type");
+  assertTrue(info.type < UI_TRANSITION_TYPE_COUNT, "Invalid type");
+  assertTrue(info.duration >= 0.0f, "Duration must be non-negative");
+
+  memoryZero(&UI_TRANSITION, sizeof(uitransition_t));
+
+  UI_TRANSITION.data.duration = info.duration;
+  UI_TRANSITION.type = info.type;
+  UI_TRANSITION.data.params = info.params;
+  UI_TRANSITION.finished = info.finished;
+  UI_TRANSITION.user = info.user;
+}

archive/dusk/ui/transition/uitransition.h

@@ -0,0 +1,74 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/color.h"
+#include "animation/easing.h"
+#include "uitransitiondata.h"
+
+typedef void (*uitransitioncallback_t)(void *user);
+
+typedef enum {
+  UI_TRANSITION_TYPE_NULL,
+
+  UI_TRANSITION_TYPE_FADE,
+
+  UI_TRANSITION_TYPE_COUNT
+} uitransitiontype_t;
+
+extern uitransitiondrawfunc_t UI_TRANSITION_TYPE_DRAW[UI_TRANSITION_TYPE_COUNT];
+
+
+typedef struct {
+  uitransitiondata_t data;
+  uitransitiontype_t type;
+  uitransitioncallback_t finished;
+  void *user;
+} uitransition_t;
+
+extern uitransition_t UI_TRANSITION;
+
+/**
+ * Initializes the transition overlay, zeroing all fields and wiring the
+ * onTransitionEnd event.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiTransitionInit(void);
+
+/**
+ * Advances the transition. Fires onTransitionEnd once when it completes.
+ * Safe to call when no transition is running.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiTransitionUpdate(void);
+
+/**
+ * Renders the transition overlay. Skipped entirely when the current alpha
+ * is zero.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiTransitionDraw(void);
+
+typedef struct {
+  float_t duration;
+  uitransitiontype_t type;
+  uitransitionparams_t params;
+  uitransitioncallback_t finished;
+  void *user;
+} uitransitionstartparams_t;
+
+/**
+ * Starts a transition described by an info struct.
+ *
+ * @param info Transition parameters.
+ */
+void uiTransitionStart(const uitransitionstartparams_t info);
+

archive/dusk/ui/transition/uitransitiondata.h

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "uitransitionfade.h"
+
+typedef union uitransitionparams_u {
+  uitransitionfade_t fade;
+} uitransitionparams_t;
+
+typedef struct uitransitiondata_s {
+  float_t time;
+  float_t duration;
+  float_t t;
+  uitransitionparams_t params;
+} uitransitiondata_t;
+
+typedef errorret_t (*uitransitiondrawfunc_t)(const uitransitiondata_t *data);

archive/dusk/ui/transition/uitransitionfade.c

@@ -0,0 +1,56 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uitransition.h"
+#include "assert/assert.h"
+#include "display/screen/screen.h"
+#include "display/texture/texture.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+
+errorret_t uiTransitionFadeDraw(const uitransitiondata_t *data) {
+  assertNotNull(data, "data must not be NULL");
+
+  float_t e = easingApply(data->params.fade.easing, data->t);
+
+  float_t r = (float_t)(
+    data->params.fade.toColor.r - data->params.fade.fromColor.r
+  ) * e;
+  float_t g = (float_t)(
+    data->params.fade.toColor.g - data->params.fade.fromColor.g
+  ) * e;
+  float_t b = (float_t)(
+    data->params.fade.toColor.b - data->params.fade.fromColor.b
+  ) * e;
+  float_t a = (float_t)(
+    data->params.fade.toColor.a - data->params.fade.fromColor.a
+  ) * e;
+
+  color_t color = color4b(
+    data->params.fade.fromColor.r + (uint8_t)r,
+    data->params.fade.fromColor.g + (uint8_t)g,
+    data->params.fade.fromColor.b + (uint8_t)b,
+    data->params.fade.fromColor.a + (uint8_t)a
+  );
+
+  if(color.a == 0) errorOk();
+
+  spritebatchsprite_t sprite = {
+    .min = { 0.0f, 0.0f, 0.0f },
+    .max = { (float_t)SCREEN.width, (float_t)SCREEN.height, 0.0f },
+    .uvMin = { 0.0f, 0.0f },
+    .uvMax = { 1.0f, 1.0f }
+  };
+  shadermaterial_t material = {
+    .unlit = {
+      .color = color,
+      .texture = NULL
+    }
+  };
+  errorChain(spriteBatchBuffer(&sprite, 1, &SHADER_UNLIT, material));
+  errorOk();
+}

archive/dusk/ui/transition/uitransitionfade.h

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/color.h"
+#include "animation/easing.h"
+
+typedef struct uitransitiondata_s uitransitiondata_t;
+
+typedef struct {
+  color_t fromColor;
+  color_t toColor;
+  easingtype_t easing;
+} uitransitionfade_t;
+
+/**
+ * Renders a full-screen color overlay interpolated between fade->fromColor
+ * and fade->toColor using fade->easing. t is the raw normalized progress
+ * in [0, 1] before easing is applied. No-op when the resulting alpha is zero.
+ *
+ * @param fade The fade parameters.
+ * @return Any error that occurs.
+ */
+errorret_t uiTransitionFadeDraw(const uitransitiondata_t *fade);

archive/dusk/ui/ui.c

@@ -0,0 +1,62 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "ui.h"
+#include "util/memory.h"
+#include "assert/assert.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/screen/screen.h"
+#include "ui/uielement.h"
+#include "ui/focus/uifocus.h"
+
+ui_t UI;
+
+errorret_t uiInit(void) {
+  memoryZero(&UI, sizeof(ui_t));
+  uiFocusInit();
+  uiElementsSort();
+
+  uielement_t *element = &UI_ELEMENTS[0];
+  while(!uiElementIsNull(element)) {
+    errorChain(uiElementInit(element));
+    element++;
+  }
+
+  errorOk();
+}
+
+errorret_t uiUpdate(void) {
+  uiFocusUpdate();
+
+  uielement_t *element = &UI_ELEMENTS[0];
+  while(!uiElementIsNull(element)) {
+    errorChain(uiElementUpdate(element));
+    element++;
+  }
+
+  errorOk();
+}
+
+errorret_t uiRender(void) {
+  const uielement_t *element = &UI_ELEMENTS[0];
+  while(!uiElementIsNull(element)) {
+    errorChain(uiElementDraw(element));
+    element++;
+  }
+
+  errorChain(spriteBatchFlush());
+  errorOk();
+}
+
+errorret_t uiDispose(void) {
+  uielement_t *element = &UI_ELEMENTS[0];
+  while(!uiElementIsNull(element)) {
+    errorChain(uiElementDispose(element));
+    element++;
+  }
+  errorOk();
+}

archive/dusk/ui/ui.h

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+
+typedef struct {
+  void *nothing;
+} ui_t;
+
+extern ui_t UI;
+
+/**
+ * Initializes the UI system.
+ */
+errorret_t uiInit(void);
+
+/**
+ * Updates the UI system.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiUpdate(void);
+
+/**
+ * Renders the UI system.
+ * 
+ * @return Any error that occurs.
+ */
+errorret_t uiRender(void);
+
+/**
+ * Disposes of the UI system.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiDispose(void);

archive/dusk/ui/uielement.c

@@ -0,0 +1,86 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uielement.h"
+#include "assert/assert.h"
+#include "util/sort.h"
+#include "ui/frame/uiframe.h"
+#include "ui/debug/uifps.h"
+#include "engine/engine.h"
+#include "ui/overlay/uifullbox.h"
+#include "ui/overlay/uiloading.h"
+#include "ui/overlay/uicrop.h"
+#include "ui/transition/uitransition.h"
+#include "ui/debug/uiconsole.h"
+#include "ui/frame/uiconfirm.h"
+
+// Priming pass: X does nothing here, so this only exists to process any
+// #include directives nested in uielementlist.h/ui/uielementgame.h at
+// file scope (each such header's own #pragma once makes it a no-op on
+// the real pass below, which happens inside UI_ELEMENTS[]'s braces,
+// where a raw #include of a declaration would be invalid).
+#define X(initFn, updateFn, drawFn, disposeFn, order) // do nothing
+#include "uielementlist.h"
+#undef X
+
+uielement_t UI_ELEMENTS[] = {
+  #define X(initFn, updateFn, drawFn, disposeFn, elementOrder) \
+    { \
+      .init = initFn, .update = updateFn, .draw = drawFn, \
+      .dispose = disposeFn, .order = elementOrder \
+    },
+  #include "uielementlist.h"
+  #undef X
+
+  { 0 } // Null terminator
+};
+
+bool_t uiElementIsNull(const uielement_t *element) {
+  return element->init == NULL &&
+    element->update == NULL &&
+    element->draw == NULL &&
+    element->dispose == NULL;
+}
+
+int_t uiElementCompareOrder(const void *a, const void *b) {
+  const uielement_t *elementA = (const uielement_t *)a;
+  const uielement_t *elementB = (const uielement_t *)b;
+  if(elementA->order < elementB->order) return -1;
+  if(elementA->order > elementB->order) return 1;
+  return 0;
+}
+
+void uiElementsSort(void) {
+  // The trailing null terminator is always the last static entry -- sort
+  // everything before it, and leave it in place.
+  const size_t count = (sizeof(UI_ELEMENTS) / sizeof(UI_ELEMENTS[0])) - 1;
+  sortBubble(UI_ELEMENTS, count, sizeof(uielement_t), uiElementCompareOrder);
+}
+
+errorret_t uiElementInit(uielement_t *element) {
+  assertNotNull(element, "element must not be NULL");
+  if(element->init != NULL) errorChain(element->init());
+  errorOk();
+}
+
+errorret_t uiElementUpdate(uielement_t *element) {
+  assertNotNull(element, "element must not be NULL");
+  if(element->update != NULL) errorChain(element->update());
+  errorOk();
+}
+
+errorret_t uiElementDraw(const uielement_t *element) {
+  assertNotNull(element, "element must not be NULL");
+  if(element->draw != NULL) errorChain(element->draw());
+  errorOk();
+}
+
+errorret_t uiElementDispose(uielement_t *element) {
+  assertNotNull(element, "element must not be NULL");
+  if(element->dispose != NULL) errorChain(element->dispose());
+  errorOk();
+}

archive/dusk/ui/uielement.h

@@ -0,0 +1,84 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+
+// Built-in order tiers. Lower values update/render first; ties preserve
+// their relative UI_ELEMENTS declaration order (uiElementsSort uses a
+// stable sort). Game-specific elements can use any int32_t value -- these
+// are just the ones the engine itself relies on.
+#define UI_ELEMENT_ORDER_DEFAULT 0
+#define UI_ELEMENT_ORDER_DEBUG   1000
+
+typedef struct {
+  errorret_t (*init)();
+  errorret_t (*update)();
+  errorret_t (*draw)();
+  errorret_t (*dispose)();
+  int32_t order;
+} uielement_t;
+
+extern uielement_t UI_ELEMENTS[];
+
+/**
+ * Returns true when all four callbacks on the element are NULL,
+ * which marks the end of the UI_ELEMENTS array.
+ *
+ * @param element The element to test.
+ * @returns True if the element is the null terminator.
+ */
+bool_t uiElementIsNull(const uielement_t *element);
+
+/**
+ * Compares two elements by their .order field, ascending. Matches
+ * sortcompare_t, for use with the project's sort utilities.
+ *
+ * @param a First uielement_t to compare.
+ * @param b Second uielement_t to compare.
+ * @return Negative if a < b, zero if a == b, positive if a > b.
+ */
+int_t uiElementCompareOrder(const void *a, const void *b);
+
+/**
+ * Stably sorts UI_ELEMENTS in place by .order, ascending. The trailing
+ * null terminator is never moved. Called once by uiInit -- element order
+ * is static after that, so there's no need to re-sort every frame.
+ */
+void uiElementsSort(void);
+
+/**
+ * Initializes a UI element, invoking its init callback if set.
+ *
+ * @param element The element to initialize.
+ * @return Any error that occurs.
+ */
+errorret_t uiElementInit(uielement_t *element);
+
+/**
+ * Updates a UI element, calling its update callback if set.
+ *
+ * @param element The element to update.
+ * @return Any error that occurs.
+ */
+errorret_t uiElementUpdate(uielement_t *element);
+
+/**
+ * Draws a UI element, calling its draw callback if set.
+ *
+ * @param element The element to render.
+ * @return Any error that occurs.
+ */
+errorret_t uiElementDraw(const uielement_t *element);
+
+/**
+ * Disposes of a UI element, invoking its dispose callback if set.
+ *
+ * @param element The element to dispose.
+ * @return Any error that occurs.
+ */
+errorret_t uiElementDispose(uielement_t *element);

archive/dusk/ui/uielementlist.h

@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+// X(init, update, draw, dispose, order) -- pass NULL for any callback the
+// element doesn't need. order controls update/draw sequence (lower first,
+// see UI_ELEMENT_ORDER_* in uielement.h); ties preserve declaration order.
+// See uielement.c for how this expands.
+
+X(uiFrameInit, NULL, NULL, uiFrameDispose, UI_ELEMENT_ORDER_DEFAULT)
+
+// Fullbox under: above scene, below system UI.
+X(
+  uiFullboxUnderInit, uiFullboxUnderUpdate, uiFullboxUnderDraw, NULL,
+  UI_ELEMENT_ORDER_DEFAULT
+)
+
+// Text stuffs
+X(uiConfirmInit, NULL, uiConfirmDraw, uiConfirmDispose, UI_ELEMENT_ORDER_DEFAULT)
+
+X(
+  uiTransitionInit, uiTransitionUpdate, uiTransitionDraw, NULL,
+  UI_ELEMENT_ORDER_DEFAULT
+)
+
+// Fullbox over: above absolutely everything (except debug).
+X(
+  uiFullboxOverInit, uiFullboxOverUpdate, uiFullboxOverDraw, NULL,
+  UI_ELEMENT_ORDER_DEFAULT
+)
+
+X(
+  uiLoadingInit, uiLoadingUpdate, uiLoadingDraw, NULL,
+  UI_ELEMENT_ORDER_DEFAULT
+)
+
+X(uiCropInit, NULL, uiCropDraw, NULL, UI_ELEMENT_ORDER_DEFAULT)
+
+// Debug items -- always last.
+X(NULL, NULL, uiConsoleDraw, uiConsoleDispose, UI_ELEMENT_ORDER_DEBUG)
+X(uiFPSInit, NULL, uiFPSDraw, NULL, UI_ELEMENT_ORDER_DEBUG)
+
+// Game-specific UI elements (duskrpg)
+#include "ui/uielementgame.h"

archive/dusk/ui/widget/CMakeLists.txt

@@ -0,0 +1,17 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uibutton.c
+    uicheckbox.c
+    uitab.c
+    uislider.c
+    uidropdown.c
+    uiscrolling.c
+    uimenu.c
+    uilabel.c
+    uiwidgetlabel.c
+)

archive/dusk/ui/widget/uibutton.c

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uibutton.h"
+#include "assert/assert.h"
+#include "display/text/text.h"
+#include "display/color.h"
+
+void uiButtonInit(uibutton_t *button, const char_t *label) {
+  assertNotNull(button, "Button cannot be NULL");
+  assertNotNull(label, "Label cannot be NULL");
+  uiWidgetLabelInit(&button->label, &FONT_DEFAULT);
+  uiWidgetLabelSetText(&button->label, label);
+  button->highlighted = false;
+}
+
+bool_t uiButtonIsHighlighted(const uibutton_t *button) {
+  assertNotNull(button, "Button cannot be NULL");
+  return button->highlighted;
+}
+
+void uiButtonSetHighlighted(uibutton_t *button, const bool_t highlighted) {
+  assertNotNull(button, "Button cannot be NULL");
+  button->highlighted = highlighted;
+  uiWidgetLabelSetColor(
+    &button->label, highlighted ? COLOR_RED : COLOR_WHITE
+  );
+}
+
+errorret_t uiButtonDraw(
+  const uibutton_t *button,
+  const float_t x,
+  const float_t y
+) {
+  assertNotNull(button, "Button cannot be NULL");
+  errorChain(uiWidgetLabelDraw(&button->label, x, y));
+  errorOk();
+}

archive/dusk/ui/widget/uibutton.h

@@ -0,0 +1,53 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uiwidgetlabel.h"
+
+typedef struct {
+  uiwidgetlabel_t label;
+  bool_t highlighted;
+} uibutton_t;
+
+/**
+ * Initializes a button.
+ *
+ * @param button The button to initialize.
+ * @param label Display label.
+ */
+void uiButtonInit(uibutton_t *button, const char_t *label);
+
+/**
+ * Returns whether the button is highlighted.
+ *
+ * @param button The button to query.
+ * @returns True if highlighted.
+ */
+bool_t uiButtonIsHighlighted(const uibutton_t *button);
+
+/**
+ * Sets the highlighted state of the button.
+ *
+ * @param button The button to update.
+ * @param highlighted The new highlighted state.
+ */
+void uiButtonSetHighlighted(uibutton_t *button, const bool_t highlighted);
+
+/**
+ * Draws the button at the given screen position.
+ *
+ * @param button The button to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiButtonDraw(
+  const uibutton_t *button,
+  const float_t x,
+  const float_t y
+);

archive/dusk/ui/widget/uicheckbox.c

@@ -0,0 +1,64 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uicheckbox.h"
+#include "util/memory.h"
+#include "util/string.h"
+#include "display/text/text.h"
+#include "display/color.h"
+
+void uiCheckboxInit(
+  uicheckbox_t *checkbox,
+  const char_t *label
+) {
+  memoryZero(checkbox, sizeof(uicheckbox_t));
+  checkbox->rawLabel = label;
+  uiWidgetLabelInit(&checkbox->label, &FONT_DEFAULT);
+  uiCheckboxRebuildLabel(checkbox);
+}
+
+bool_t uiCheckboxIsChecked(const uicheckbox_t *checkbox) {
+  return checkbox->checked;
+}
+
+void uiCheckboxSetChecked(uicheckbox_t *checkbox, const bool_t checked) {
+  checkbox->checked = checked;
+  uiCheckboxRebuildLabel(checkbox);
+}
+
+void uiCheckboxToggle(uicheckbox_t *checkbox) {
+  uiCheckboxSetChecked(checkbox, !uiCheckboxIsChecked(checkbox));
+}
+
+bool_t uiCheckboxIsHighlighted(const uicheckbox_t *checkbox) {
+  return checkbox->highlighted;
+}
+
+void uiCheckboxSetHighlighted(uicheckbox_t *checkbox, const bool_t highlighted) {
+  checkbox->highlighted = highlighted;
+  uiWidgetLabelSetColor(
+    &checkbox->label, highlighted ? COLOR_RED : COLOR_WHITE
+  );
+}
+
+errorret_t uiCheckboxDraw(
+  const uicheckbox_t *checkbox,
+  const float_t x,
+  const float_t y
+) {
+  errorChain(uiWidgetLabelDraw(&checkbox->label, x, y));
+  errorOk();
+}
+
+void uiCheckboxRebuildLabel(uicheckbox_t *checkbox) {
+  char_t combined[UI_WIDGET_LABEL_TEXT_MAX];
+  stringFormat(
+    combined, UI_WIDGET_LABEL_TEXT_MAX - 1, "%s %s",
+    checkbox->checked ? "Y" : "N", checkbox->rawLabel
+  );
+  uiWidgetLabelSetText(&checkbox->label, combined);
+}

archive/dusk/ui/widget/uicheckbox.h

@@ -0,0 +1,90 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uiwidgetlabel.h"
+
+typedef struct uicheckbox_s {
+  const char_t *rawLabel;
+  uiwidgetlabel_t label;
+  bool_t checked;
+  bool_t highlighted;
+} uicheckbox_t;
+
+/**
+ * Initializes a checkbox.
+ *
+ * @param checkbox The checkbox to initialize.
+ * @param label Display label.
+ */
+void uiCheckboxInit(
+  uicheckbox_t *checkbox,
+  const char_t *label
+);
+
+/**
+ * Returns whether the checkbox is checked.
+ *
+ * @param checkbox The checkbox to query.
+ * @returns True if checked.
+ */
+bool_t uiCheckboxIsChecked(const uicheckbox_t *checkbox);
+
+/**
+ * Sets the checked state of the checkbox.
+ *
+ * @param checkbox The checkbox to update.
+ * @param checked The new checked state.
+ */
+void uiCheckboxSetChecked(uicheckbox_t *checkbox, const bool_t checked);
+
+/**
+ * Toggles the checked state of the checkbox.
+ *
+ * @param checkbox The checkbox to toggle.
+ */
+void uiCheckboxToggle(uicheckbox_t *checkbox);
+
+/**
+ * Returns whether the checkbox is highlighted.
+ *
+ * @param checkbox The checkbox to query.
+ * @returns True if highlighted.
+ */
+bool_t uiCheckboxIsHighlighted(const uicheckbox_t *checkbox);
+
+/**
+ * Sets the highlighted state of the checkbox.
+ *
+ * @param checkbox The checkbox to update.
+ * @param highlighted The new highlighted state.
+ */
+void uiCheckboxSetHighlighted(uicheckbox_t *checkbox, const bool_t highlighted);
+
+/**
+ * Draws the checkbox at the given screen position.
+ *
+ * @param checkbox The checkbox to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiCheckboxDraw(
+  const uicheckbox_t *checkbox,
+  const float_t x,
+  const float_t y
+);
+
+/**
+ * Rebuilds the checkbox's cached label ("Y "/"N " mark plus rawLabel)
+ * from its current checked state. Called internally whenever checked
+ * changes.
+ *
+ * @param checkbox The checkbox to update.
+ */
+void uiCheckboxRebuildLabel(uicheckbox_t *checkbox);

archive/dusk/ui/widget/uidropdown.c

@@ -0,0 +1,110 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uidropdown.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/string.h"
+#include "display/text/text.h"
+#include "display/color.h"
+
+void uiDropdownInit(
+  uidropdown_t *dropdown,
+  const char_t *label,
+  const char_t *const *options,
+  const uint8_t optionCount,
+  const uint8_t selectedIndex
+) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(options, "Options cannot be NULL");
+  assertTrue(optionCount > 0, "Dropdown must have at least one option");
+
+  memoryZero(dropdown, sizeof(uidropdown_t));
+  uiWidgetLabelInit(&dropdown->label, &FONT_DEFAULT);
+  uiWidgetLabelSetText(&dropdown->label, label);
+  uiWidgetLabelInit(&dropdown->value, &FONT_DEFAULT);
+  dropdown->options = options;
+  dropdown->optionCount = optionCount;
+  dropdown->selectedIndex = selectedIndex < optionCount ? selectedIndex : 0;
+  uiDropdownRebuildValue(dropdown);
+}
+
+uint8_t uiDropdownGetSelectedIndex(const uidropdown_t *dropdown) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  return dropdown->selectedIndex;
+}
+
+const char_t *uiDropdownGetSelectedOption(const uidropdown_t *dropdown) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  return dropdown->options[dropdown->selectedIndex];
+}
+
+void uiDropdownSetSelectedIndex(uidropdown_t *dropdown, const uint8_t index) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  assertTrue(index < dropdown->optionCount, "Dropdown index out of range");
+  dropdown->selectedIndex = index;
+  uiDropdownRebuildValue(dropdown);
+}
+
+void uiDropdownStepNext(uidropdown_t *dropdown) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  dropdown->selectedIndex =
+    (dropdown->selectedIndex + 1) % dropdown->optionCount;
+  uiDropdownRebuildValue(dropdown);
+}
+
+void uiDropdownStepPrev(uidropdown_t *dropdown) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  dropdown->selectedIndex = dropdown->selectedIndex == 0 ?
+    dropdown->optionCount - 1 : dropdown->selectedIndex - 1;
+  uiDropdownRebuildValue(dropdown);
+}
+
+bool_t uiDropdownIsHighlighted(const uidropdown_t *dropdown) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  return dropdown->highlighted;
+}
+
+void uiDropdownSetHighlighted(
+  uidropdown_t *dropdown,
+  const bool_t highlighted
+) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+  dropdown->highlighted = highlighted;
+  color_t color = highlighted ? COLOR_RED : COLOR_WHITE;
+  uiWidgetLabelSetColor(&dropdown->label, color);
+  uiWidgetLabelSetColor(&dropdown->value, color);
+}
+
+errorret_t uiDropdownDraw(
+  const uidropdown_t *dropdown,
+  const float_t x,
+  const float_t y
+) {
+  assertNotNull(dropdown, "Dropdown cannot be NULL");
+
+  errorChain(uiWidgetLabelDraw(&dropdown->label, x, y));
+
+  int32_t labelW, labelH;
+  uiWidgetLabelGetSize(&dropdown->label, &labelW, &labelH);
+
+  errorChain(uiWidgetLabelDraw(
+    &dropdown->value, x + (float_t)labelW + UI_DROPDOWN_GAP, y
+  ));
+
+  errorOk();
+}
+
+void uiDropdownRebuildValue(uidropdown_t *dropdown) {
+  char_t valueText[UI_WIDGET_LABEL_TEXT_MAX];
+  stringFormat(
+    valueText, UI_WIDGET_LABEL_TEXT_MAX - 1, "< %s >",
+    uiDropdownGetSelectedOption(dropdown)
+  );
+  uiWidgetLabelSetText(&dropdown->value, valueText);
+}

archive/dusk/ui/widget/uidropdown.h

@@ -0,0 +1,123 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uiwidgetlabel.h"
+
+#define UI_DROPDOWN_GAP 4.0f
+
+typedef struct {
+  uiwidgetlabel_t label;
+  uiwidgetlabel_t value;
+  const char_t *const *options;
+  uint8_t optionCount;
+  uint8_t selectedIndex;
+  bool_t highlighted;
+} uidropdown_t;
+
+/**
+ * Initializes a dropdown.
+ *
+ * @param dropdown The dropdown to initialize.
+ * @param label Display label.
+ * @param options Array of option display strings; caller-owned, must
+ * outlive the dropdown.
+ * @param optionCount Number of entries in options. Must be > 0.
+ * @param selectedIndex Initial selected option index, clamped to
+ * [0, optionCount - 1].
+ */
+void uiDropdownInit(
+  uidropdown_t *dropdown,
+  const char_t *label,
+  const char_t *const *options,
+  const uint8_t optionCount,
+  const uint8_t selectedIndex
+);
+
+/**
+ * Returns the index of the currently selected option.
+ *
+ * @param dropdown The dropdown to query.
+ * @returns The selected option index.
+ */
+uint8_t uiDropdownGetSelectedIndex(const uidropdown_t *dropdown);
+
+/**
+ * Returns the currently selected option's display string.
+ *
+ * @param dropdown The dropdown to query.
+ * @returns The selected option string.
+ */
+const char_t *uiDropdownGetSelectedOption(const uidropdown_t *dropdown);
+
+/**
+ * Sets the selected option by index.
+ *
+ * @param dropdown The dropdown to update.
+ * @param index The new selected option index. Must be < optionCount.
+ */
+void uiDropdownSetSelectedIndex(uidropdown_t *dropdown, const uint8_t index);
+
+/**
+ * Selects the next option, wrapping around to the first option past
+ * the last.
+ *
+ * @param dropdown The dropdown to update.
+ */
+void uiDropdownStepNext(uidropdown_t *dropdown);
+
+/**
+ * Selects the previous option, wrapping around to the last option
+ * before the first.
+ *
+ * @param dropdown The dropdown to update.
+ */
+void uiDropdownStepPrev(uidropdown_t *dropdown);
+
+/**
+ * Returns whether the dropdown is highlighted.
+ *
+ * @param dropdown The dropdown to query.
+ * @returns True if highlighted.
+ */
+bool_t uiDropdownIsHighlighted(const uidropdown_t *dropdown);
+
+/**
+ * Sets the highlighted state of the dropdown.
+ *
+ * @param dropdown The dropdown to update.
+ * @param highlighted The new highlighted state.
+ */
+void uiDropdownSetHighlighted(
+  uidropdown_t *dropdown,
+  const bool_t highlighted
+);
+
+/**
+ * Draws the dropdown at the given screen position: label, then the
+ * currently selected option surrounded by cycle arrows.
+ *
+ * @param dropdown The dropdown to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiDropdownDraw(
+  const uidropdown_t *dropdown,
+  const float_t x,
+  const float_t y
+);
+
+/**
+ * Rebuilds the dropdown's cached value label ("< option >") from its
+ * current selectedIndex. Called internally whenever selectedIndex
+ * changes.
+ *
+ * @param dropdown The dropdown to update.
+ */
+void uiDropdownRebuildValue(uidropdown_t *dropdown);

archive/dusk/ui/widget/uilabel.c

@@ -0,0 +1,70 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uilabel.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/string.h"
+#include "display/text/text.h"
+
+void uiLabelInit(uilabel_t *label, font_t *font) {
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(font, "Font cannot be NULL");
+
+  memoryZero(label, sizeof(uilabel_t));
+  label->font = font;
+  label->color = COLOR_WHITE;
+}
+
+void uiLabelSetText(uilabel_t *label, const char_t *text) {
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(text, "Text cannot be NULL");
+  assertStrLenMax(text, UI_LABEL_TEXT_MAX, "Label text too long");
+
+  stringCopy(label->text, text, UI_LABEL_TEXT_MAX);
+  label->spriteCount = textBuildSpriteCache(
+    label->text, label->font, label->sprites, UI_LABEL_SPRITE_COUNT_MAX,
+    &label->width, &label->height
+  );
+}
+
+void uiLabelSetColor(uilabel_t *label, const color_t color) {
+  assertNotNull(label, "Label cannot be NULL");
+  label->color = color;
+}
+
+void uiLabelGetSize(
+  const uilabel_t *label,
+  int32_t *outWidth,
+  int32_t *outHeight
+) {
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(outWidth, "Output width cannot be NULL");
+  assertNotNull(outHeight, "Output height cannot be NULL");
+  *outWidth = label->width;
+  *outHeight = label->height;
+}
+
+errorret_t uiLabelDraw(
+  const uilabel_t *label,
+  const float_t x,
+  const float_t y
+) {
+  assertNotNull(label, "Label cannot be NULL");
+  if(label->spriteCount == 0) errorOk();
+
+  // Cached sprites are relative to (0,0); textDrawSpriteCache translates
+  // into the requested screen position here instead of in
+  // uiLabelSetText, so a label can be repositioned every frame without
+  // rebuilding the (much more expensive) glyph/UV cache.
+  spritebatchsprite_t scratch[UI_LABEL_SPRITE_COUNT_MAX];
+  errorChain(textDrawSpriteCache(
+    label->sprites, label->spriteCount, scratch, x, y, label->color,
+    label->font->texture
+  ));
+  errorOk();
+}

archive/dusk/ui/widget/uilabel.h

@@ -0,0 +1,85 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/text/font.h"
+#include "display/spritebatch/spritebatchsprite.h"
+#include "display/color.h"
+
+#define UI_LABEL_TEXT_MAX 256
+#define UI_LABEL_SPRITE_COUNT_MAX UI_LABEL_TEXT_MAX
+
+typedef struct {
+  char_t text[UI_LABEL_TEXT_MAX];
+  color_t color;
+  font_t *font;
+
+  spritebatchsprite_t sprites[UI_LABEL_SPRITE_COUNT_MAX];
+  uint32_t spriteCount;
+  int32_t width;
+  int32_t height;
+} uilabel_t;
+
+/**
+ * Initializes a label, defaulting to white text and no text set.
+ *
+ * @param label The label to initialize.
+ * @param font Font to use for rendering. Must outlive the label.
+ */
+void uiLabelInit(uilabel_t *label, font_t *font);
+
+/**
+ * Sets the label's text, rebuilding its cached sprites (glyph lookup, UV,
+ * and layout) immediately. This is the only way the sprite cache gets
+ * rebuilt -- uiLabelDraw never recomputes it, so call this whenever the
+ * text changes rather than once up front and expecting it to stay in sync.
+ *
+ * @param label The label to update.
+ * @param text Null-terminated string to display. Must be shorter than
+ * UI_LABEL_TEXT_MAX.
+ */
+void uiLabelSetText(uilabel_t *label, const char_t *text);
+
+/**
+ * Sets the label's tint color. Cheap -- doesn't touch the sprite cache,
+ * since color is applied via the draw material, not baked into sprites.
+ *
+ * @param label The label to update.
+ * @param color The new tint color.
+ */
+void uiLabelSetColor(uilabel_t *label, const color_t color);
+
+/**
+ * Gets the measured size (in pixels) of the label's current text, cached
+ * from the last uiLabelSetText call.
+ *
+ * @param label The label to query.
+ * @param outWidth Pointer to store the width.
+ * @param outHeight Pointer to store the height.
+ */
+void uiLabelGetSize(
+  const uilabel_t *label,
+  int32_t *outWidth,
+  int32_t *outHeight
+);
+
+/**
+ * Draws the label's cached sprites at the given screen position in a
+ * single batched buffer call. Does not recompute glyph layout -- call
+ * uiLabelSetText first whenever the text changes.
+ *
+ * @param label The label to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiLabelDraw(
+  const uilabel_t *label,
+  const float_t x,
+  const float_t y
+);

archive/dusk/ui/widget/uimenu.c

@@ -0,0 +1,293 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uimenu.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "display/text/text.h"
+#include "display/color.h"
+#include "ui/widget/uiwidgetlabel.h"
+#include "ui/widget/uibutton.h"
+#include "ui/widget/uitab.h"
+#include "ui/widget/uislider.h"
+#include "ui/widget/uidropdown.h"
+
+void uiMenuInit(
+  uimenu_t *menu,
+  uimenuselectedcallback_t selected,
+  uimenuclosedcallback_t closed,
+  uimenuchangedcallback_t changed
+) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  memoryZero(menu, sizeof(uimenu_t));
+  menu->selected = selected;
+  menu->closed = closed;
+  menu->changed = changed;
+}
+
+void uiMenuSetItems(
+  uimenu_t *menu,
+  const uimenuitem_t *items,
+  const uint8_t itemCount,
+  const uint8_t columns
+) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  assertNotNull(items, "Items cannot be NULL");
+  assertTrue(itemCount > 0, "Item count must be > 0");
+  assertTrue(columns > 0, "Columns must be > 0");
+  menu->items = (uimenuitem_t *)items;
+  menu->itemCount = itemCount;
+  menu->columns = columns;
+}
+
+void uiMenuSetPosition(uimenu_t *menu, const uint8_t x, const uint8_t y) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  if(menu->focusItem == NULL) return;
+  uiFocusSetPosition(menu->focusItem, x, y);
+}
+
+void uiMenuOpen(uimenu_t *menu) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  assertNotNull(menu->items, "Menu items cannot be NULL");
+  assertTrue(menu->itemCount > 0, "Menu item count must be > 0");
+  assertTrue(menu->columns > 0, "Menu columns must be > 0");
+  if(menu->focusItem != NULL) return;
+
+  uint8_t focusable = uiMenuFocusableCount(menu);
+  uint8_t rows = focusable > 0 ?
+    (focusable + menu->columns - 1) / menu->columns : 1;
+  menu->focusItem = uiFocusPush(
+    menu->columns, rows,
+    uiMenuFocusSelected,
+    uiMenuFocusChanged,
+    uiMenuFocusClosed,
+    uiMenuFocusDirection,
+    menu
+  );
+}
+
+void uiMenuClose(uimenu_t *menu) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  if(menu->focusItem == NULL) return;
+  uiFocusPopItem(menu->focusItem);
+  menu->focusItem = NULL;
+}
+
+bool_t uiMenuIsActive(const uimenu_t *menu) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  return menu->focusItem != NULL;
+}
+
+errorret_t uiMenuDraw(
+  const uimenu_t *menu,
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  if(menu->itemCount == 0) errorOk();
+
+  float_t colStep = width / (float_t)menu->columns;
+  float_t rowHeight = (float_t)FONT_DEFAULT.tileset->tileHeight;
+
+  uint8_t col = 0;
+  uint8_t row = 0;
+
+  for(uint8_t i = 0; i < menu->itemCount; i++) {
+    const uimenuitem_t *item = &menu->items[i];
+
+    if(item->type == UI_MENU_WIDGET_TYPE_LABEL) {
+      if(col > 0) { row++; col = 0; }
+      errorChain(uiWidgetLabelDraw(
+        &item->label, x, y + (float_t)row * rowHeight
+      ));
+      row++;
+      continue;
+    }
+
+    if(item->type == UI_MENU_WIDGET_TYPE_SPACER) {
+      if(col > 0) { row++; col = 0; }
+      row++;
+      continue;
+    }
+
+    float_t ix = x + (float_t)col * colStep;
+    float_t iy = y + (float_t)row * rowHeight;
+
+    switch(item->type) {
+      case UI_MENU_WIDGET_TYPE_CHECKBOX:
+        errorChain(uiCheckboxDraw(&item->checkbox, ix, iy));
+        break;
+
+      case UI_MENU_WIDGET_TYPE_BUTTON:
+        errorChain(uiButtonDraw(&item->button, ix, iy));
+        break;
+
+      case UI_MENU_WIDGET_TYPE_TAB:
+        errorChain(uiTabDraw(&item->tab, ix, iy));
+        break;
+
+      case UI_MENU_WIDGET_TYPE_SLIDER:
+        errorChain(uiSliderDraw(&item->slider, ix, iy));
+        break;
+
+      case UI_MENU_WIDGET_TYPE_DROPDOWN:
+        errorChain(uiDropdownDraw(&item->dropdown, ix, iy));
+        break;
+
+      default:
+        break;
+    }
+
+    col++;
+    if(col >= menu->columns) { col = 0; row++; }
+  }
+
+  errorOk();
+}
+
+bool_t uiMenuFocusSelected(const uifocusitem_t *focusItem) {
+  assertNotNull(focusItem, "Focus item cannot be NULL");
+  assertNotNull(focusItem->user, "Focus item user cannot be NULL");
+  uimenu_t *menu = (uimenu_t *)focusItem->user;
+  if(menu->selected == NULL) return true;
+
+  uint8_t slot = focusItem->y * menu->columns + focusItem->x;
+  uint8_t index = uiMenuFocusSlotToIndex(menu, slot);
+  if(index == 0xFF) return true;
+
+  menu->selected(menu, index, &menu->items[index]);
+  return true;
+}
+
+bool_t uiMenuFocusChanged(const uifocusitem_t *focusItem) {
+  assertNotNull(focusItem, "Focus item cannot be NULL");
+  assertNotNull(focusItem->user, "Focus item user cannot be NULL");
+  uimenu_t *menu = (uimenu_t *)focusItem->user;
+
+  uint8_t focusSlot = focusItem->y * menu->columns + focusItem->x;
+  uint8_t slot = 0;
+
+  for(uint8_t i = 0; i < menu->itemCount; i++) {
+    uimenuitem_t *item = &menu->items[i];
+    if(
+      item->type == UI_MENU_WIDGET_TYPE_LABEL ||
+      item->type == UI_MENU_WIDGET_TYPE_SPACER
+    ) continue;
+    uiMenuItemSetHighlighted(item, slot == focusSlot);
+    slot++;
+  }
+
+  if(menu->changed == NULL) return true;
+  uint8_t index = uiMenuFocusSlotToIndex(menu, focusSlot);
+  if(index == 0xFF) return true;
+
+  menu->changed(menu, index, &menu->items[index]);
+  return true;
+}
+
+bool_t uiMenuFocusClosed(const uifocusitem_t *focusItem) {
+  assertNotNull(focusItem, "Focus item cannot be NULL");
+  assertNotNull(focusItem->user, "Focus item user cannot be NULL");
+  uimenu_t *menu = (uimenu_t *)focusItem->user;
+  menu->focusItem = NULL;
+
+  for(uint8_t i = 0; i < menu->itemCount; i++) {
+    uiMenuItemSetHighlighted(&menu->items[i], false);
+  }
+
+  if(menu->closed != NULL) menu->closed(menu);
+  return true;
+}
+
+bool_t uiMenuFocusDirection(
+  const uifocusitem_t *focusItem,
+  const uifocusdirection_t direction
+) {
+  assertNotNull(focusItem, "Focus item cannot be NULL");
+  assertNotNull(focusItem->user, "Focus item user cannot be NULL");
+  if(direction != UI_FOCUS_DIRECTION_LEFT && direction != UI_FOCUS_DIRECTION_RIGHT) {
+    return false;
+  }
+
+  uimenu_t *menu = (uimenu_t *)focusItem->user;
+  uint8_t slot = focusItem->y * menu->columns + focusItem->x;
+  uint8_t index = uiMenuFocusSlotToIndex(menu, slot);
+  if(index == 0xFF) return false;
+
+  uimenuitem_t *item = &menu->items[index];
+  bool_t right = direction == UI_FOCUS_DIRECTION_RIGHT;
+
+  if(item->type == UI_MENU_WIDGET_TYPE_SLIDER) {
+    if(right) {
+      uiSliderStepUp(&item->slider);
+    } else {
+      uiSliderStepDown(&item->slider);
+    }
+    return true;
+  }
+
+  if(item->type == UI_MENU_WIDGET_TYPE_CHECKBOX) {
+    uiCheckboxToggle(&item->checkbox);
+    return true;
+  }
+
+  if(item->type == UI_MENU_WIDGET_TYPE_DROPDOWN) {
+    if(right) {
+      uiDropdownStepNext(&item->dropdown);
+    } else {
+      uiDropdownStepPrev(&item->dropdown);
+    }
+    return true;
+  }
+
+  return false;
+}
+
+uint8_t uiMenuFocusableCount(const uimenu_t *menu) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  uint8_t count = 0;
+  for(uint8_t i = 0; i < menu->itemCount; i++) {
+    uimenuwidgettype_t t = menu->items[i].type;
+    if(t != UI_MENU_WIDGET_TYPE_LABEL && t != UI_MENU_WIDGET_TYPE_SPACER) count++;
+  }
+  return count;
+}
+
+uint8_t uiMenuFocusSlotToIndex(const uimenu_t *menu, const uint8_t slot) {
+  assertNotNull(menu, "Menu cannot be NULL");
+  uint8_t focusable = 0;
+  for(uint8_t i = 0; i < menu->itemCount; i++) {
+    uimenuwidgettype_t t = menu->items[i].type;
+    if(t == UI_MENU_WIDGET_TYPE_LABEL || t == UI_MENU_WIDGET_TYPE_SPACER) continue;
+    if(focusable == slot) return i;
+    focusable++;
+  }
+  return 0xFF;
+}
+
+void uiMenuLabelInit(uimenuitem_t *item, const char_t *text) {
+  assertNotNull(item, "Item cannot be NULL");
+  assertNotNull(text, "Text cannot be NULL");
+  uiWidgetLabelInit(&item->label, &FONT_DEFAULT);
+  uiWidgetLabelSetText(&item->label, text);
+}
+
+void uiMenuItemSetHighlighted(uimenuitem_t *item, const bool_t highlighted) {
+  if(item->type == UI_MENU_WIDGET_TYPE_CHECKBOX) {
+    uiCheckboxSetHighlighted(&item->checkbox, highlighted);
+  } else if(item->type == UI_MENU_WIDGET_TYPE_BUTTON) {
+    uiButtonSetHighlighted(&item->button, highlighted);
+  } else if(item->type == UI_MENU_WIDGET_TYPE_TAB) {
+    uiTabSetActive(&item->tab, highlighted);
+  } else if(item->type == UI_MENU_WIDGET_TYPE_SLIDER) {
+    uiSliderSetHighlighted(&item->slider, highlighted);
+  } else if(item->type == UI_MENU_WIDGET_TYPE_DROPDOWN) {
+    uiDropdownSetHighlighted(&item->dropdown, highlighted);
+  }
+}

archive/dusk/ui/widget/uimenu.h

@@ -0,0 +1,292 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/focus/uifocus.h"
+#include "ui/widget/uiwidgetlabel.h"
+#include "ui/widget/uibutton.h"
+#include "ui/widget/uicheckbox.h"
+#include "ui/widget/uitab.h"
+#include "ui/widget/uislider.h"
+#include "ui/widget/uidropdown.h"
+
+typedef struct uimenu_s uimenu_t;
+
+typedef enum {
+  UI_MENU_WIDGET_TYPE_NONE,
+  UI_MENU_WIDGET_TYPE_LABEL,
+  UI_MENU_WIDGET_TYPE_SPACER,
+  UI_MENU_WIDGET_TYPE_CHECKBOX,
+  UI_MENU_WIDGET_TYPE_BUTTON,
+  UI_MENU_WIDGET_TYPE_TAB,
+  UI_MENU_WIDGET_TYPE_SLIDER,
+  UI_MENU_WIDGET_TYPE_DROPDOWN,
+} uimenuwidgettype_t;
+
+typedef struct {
+  uimenuwidgettype_t type;
+  union {
+    uiwidgetlabel_t label;
+    uicheckbox_t checkbox;
+    uibutton_t button;
+    uitab_t tab;
+    uislider_t slider;
+    uidropdown_t dropdown;
+  };
+} uimenuitem_t;
+
+typedef void (*uimenuselectedcallback_t)(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+);
+
+typedef void (*uimenuchangedcallback_t)(
+  const uimenu_t *menu,
+  const uint8_t index,
+  const uimenuitem_t *item
+);
+
+typedef void (*uimenuclosedcallback_t)(const uimenu_t *menu);
+
+typedef struct uimenu_s {
+  uimenuitem_t *items;
+  uint8_t itemCount;
+  uint8_t columns;
+  uifocusitem_t *focusItem;
+
+  uimenuselectedcallback_t selected;
+  uimenuclosedcallback_t closed;
+  uimenuchangedcallback_t changed;
+
+  void *user;
+} uimenu_t;
+
+/**
+ * Initializes a menu, clearing all items and focus state.
+ *
+ * @param menu The menu to initialize.
+ * @param items The list of items to display in the menu.
+ * @param itemCount The number of items in the list.
+ * @param columns The number of columns to display the items in.
+ * @param selected The callback to invoke when an item is selected.
+ * @param closed The callback to invoke when the menu is closed.
+ * @param changed The callback to invoke when the menu changes.
+ */
+void uiMenuInit(
+  uimenu_t *menu,
+  uimenuselectedcallback_t selected,
+  uimenuclosedcallback_t closed,
+  uimenuchangedcallback_t changed
+);
+
+/**
+ * Sets the items to display in the menu.
+ *
+ * @param menu The menu to update.
+ * @param items The list of items to display in the menu.
+ * @param itemCount The number of items in the list.
+ * @param columns The number of columns to display the items in.
+ */
+void uiMenuSetItems(
+  uimenu_t *menu,
+  const uimenuitem_t *items,
+  const uint8_t itemCount,
+  const uint8_t columns
+);
+
+/**
+ * Sets the position of the menu on the screen.
+ *
+ * @param menu The menu to position.
+ * @param x The x-coordinate to position the menu at.
+ * @param y The y-coordinate to position the menu at.
+ */
+void uiMenuSetPosition(uimenu_t *menu, const uint8_t x, const uint8_t y);
+
+/**
+ * Pushes a menu onto the UI focus stack, making it the active menu.
+ *
+ * @param menu The menu to push.
+ */
+void uiMenuOpen(uimenu_t *menu);
+
+/**
+ * Pops a menu from the UI focus stack, removing it from the active menu.
+ * 
+ * @param menu The menu to pop.
+ */
+void uiMenuClose(uimenu_t *menu);
+
+/**
+ * Returns whether the menu is currently active (on the UI focus stack).
+ *
+ * @param menu The menu to query.
+ * @returns True if the menu is active.
+ */
+bool_t uiMenuIsActive(const uimenu_t *menu);
+
+/**
+ * Draws the menu at the specified position and size.
+ *
+ * @param menu The menu to draw.
+ * @param x The x-coordinate to draw the menu at.
+ * @param y The y-coordinate to draw the menu at.
+ * @param width The width of the menu.
+ * @param height The height of the menu.
+ * @returns An error code indicating success or failure.
+ */
+errorret_t uiMenuDraw(
+  const uimenu_t *menu,
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+);
+
+/**
+ * Returns the number of focusable (non-label) items in the menu.
+ *
+ * @param menu The menu to query.
+ * @returns Count of non-label items.
+ */
+uint8_t uiMenuFocusableCount(const uimenu_t *menu);
+
+/**
+ * Maps a flat focus slot index to the corresponding item array index,
+ * skipping over label items which are not focusable.
+ *
+ * @param menu The menu to query.
+ * @param slot The focus slot index (y * columns + x).
+ * @returns The item array index, or 0xFF if out of range.
+ */
+uint8_t uiMenuFocusSlotToIndex(const uimenu_t *menu, const uint8_t slot);
+
+/**
+ * Sets the highlighted/active state on a menu item, dispatching to the
+ * matching widget's setter based on its type. No-op for label/spacer
+ * items and any other type with no highlight concept.
+ *
+ * @param item The item to update.
+ * @param highlighted The new highlighted/active state.
+ */
+void uiMenuItemSetHighlighted(uimenuitem_t *item, const bool_t highlighted);
+
+/**
+ * Initializes a menu item as a standalone label, caching its text.
+ * Used internally by the MENU_LABEL helper macro.
+ *
+ * @param item The item to initialize.
+ * @param text Display text.
+ */
+void uiMenuLabelInit(uimenuitem_t *item, const char_t *text);
+
+/**
+ * Internal focus callback  -  forwards selection to the menu's selected handler.
+ *
+ * @param focusItem The active focus item; user field must point to uimenu_t.
+ * @returns True.
+ */
+bool_t uiMenuFocusSelected(const uifocusitem_t *focusItem);
+
+/**
+ * Internal focus callback  -  updates widget highlights and fires changed.
+ *
+ * @param focusItem The active focus item; user field must point to uimenu_t.
+ * @returns True.
+ */
+bool_t uiMenuFocusChanged(const uifocusitem_t *focusItem);
+
+/**
+ * Internal focus callback  -  clears focusItem and fires the closed handler.
+ *
+ * @param focusItem The active focus item; user field must point to uimenu_t.
+ * @returns True.
+ */
+bool_t uiMenuFocusClosed(const uifocusitem_t *focusItem);
+
+/**
+ * Internal focus callback  -  gives the focused item's widget a chance to
+ * handle LEFT/RIGHT itself (e.g. a slider adjusting its value) before
+ * falling back to the default cell-to-cell movement.
+ *
+ * @param focusItem The active focus item; user field must point to uimenu_t.
+ * @param direction The direction that was pressed or held.
+ * @returns True if the focused widget handled the direction.
+ */
+bool_t uiMenuFocusDirection(
+  const uifocusitem_t *focusItem,
+  const uifocusdirection_t direction
+);
+
+// Helper macros
+#define MENU_BEGIN(menuPtr, itemsArray, selected, closed, changed) \
+  uimenu_t *menu = (menuPtr); \
+  uiMenuInit(menu, selected, closed, changed); \
+  menu->items = (itemsArray); \
+  uint8_t menuIndex = 0; \
+  uint8_t menuCapacity = sizeof(itemsArray) / sizeof((itemsArray)[0])
+
+#define MENU_LABEL(text) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_LABEL; \
+  uiMenuLabelInit(&menu->items[menuIndex], text); \
+  ++menuIndex
+
+#define MENU_SPACER() \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_SPACER; \
+  ++menuIndex
+
+#define MENU_CHECKBOX(label) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_CHECKBOX; \
+  uiCheckboxInit(&menu->items[menuIndex].checkbox, label); \
+  ++menuIndex
+
+#define MENU_BUTTON(label) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_BUTTON; \
+  uiButtonInit(&menu->items[menuIndex].button, label); \
+  ++menuIndex
+
+#define MENU_TAB(label) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_TAB; \
+  uiTabInit(&menu->items[menuIndex].tab, label); \
+  ++menuIndex
+
+#define MENU_SLIDER_FLOAT(label, value, min, max, step) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_SLIDER; \
+  uiSliderInitFloat( \
+    &menu->items[menuIndex].slider, label, value, min, max, step \
+  ); \
+  ++menuIndex
+
+#define MENU_SLIDER_INT(label, value, min, max, step) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_SLIDER; \
+  uiSliderInitInt( \
+    &menu->items[menuIndex].slider, label, value, min, max, step \
+  ); \
+  ++menuIndex
+
+#define MENU_DROPDOWN(label, options, optionCount, selectedIndex) \
+  assertTrue(menuIndex < menuCapacity, "Menu item count exceeds capacity"); \
+  menu->items[menuIndex].type = UI_MENU_WIDGET_TYPE_DROPDOWN; \
+  uiDropdownInit( \
+    &menu->items[menuIndex].dropdown, label, options, optionCount, \
+    selectedIndex \
+  ); \
+  ++menuIndex
+
+#define MENU_END(itemsArray, columns) \
+  uiMenuSetItems(menu, (itemsArray), menuIndex, (columns))
+
+//EOF

archive/dusk/ui/widget/uiscrolling.c

@@ -0,0 +1,15 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiscrolling.h"
+#include "assert/assert.h"
+
+void uiScrollingInit(uiscrolling_t *scrolling) {
+  assertNotNull(scrolling, "Scrolling container cannot be NULL");
+  // Nothing to initialize yet -- uiscrolling_t is currently a
+  // placeholder with no fields.
+}

archive/dusk/ui/widget/uiscrolling.h

@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+
+typedef struct {
+
+} uiscrolling_t;
+
+/**
+ * Initializes a scrolling container. Currently a placeholder -- no
+ * scrolling behavior is implemented yet.
+ *
+ * @param scrolling The scrolling container to initialize.
+ */
+void uiScrollingInit(uiscrolling_t *scrolling);

archive/dusk/ui/widget/uislider.c

@@ -0,0 +1,282 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uislider.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/math.h"
+#include "util/string.h"
+#include "display/text/text.h"
+#include "display/color.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/texture/texture.h"
+#include "display/shader/shaderunlit.h"
+
+void uiSliderInitFloat(
+  uislider_t *slider,
+  const char_t *label,
+  const float_t value,
+  const float_t min,
+  const float_t max,
+  const float_t step
+) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  assertNotNull(label, "Label cannot be NULL");
+  assertTrue(max > min, "Slider max must be greater than min");
+  assertTrue(step > 0.0f, "Slider step must be greater than zero");
+
+  memoryZero(slider, sizeof(uislider_t));
+  uiWidgetLabelInit(&slider->label, &FONT_DEFAULT);
+  uiWidgetLabelSetText(&slider->label, label);
+  uiWidgetLabelInit(&slider->valueLabel, &FONT_DEFAULT);
+  slider->type = UI_SLIDER_TYPE_FLOAT;
+  slider->min.f = min;
+  slider->max.f = max;
+  slider->step.f = step;
+  slider->value.f = mathClamp(value, min, max);
+  uiSliderRebuildValueLabel(slider);
+  uiSliderRebuildGeometry(slider);
+}
+
+void uiSliderInitInt(
+  uislider_t *slider,
+  const char_t *label,
+  const int32_t value,
+  const int32_t min,
+  const int32_t max,
+  const int32_t step
+) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  assertNotNull(label, "Label cannot be NULL");
+  assertTrue(max > min, "Slider max must be greater than min");
+  assertTrue(step > 0, "Slider step must be greater than zero");
+
+  memoryZero(slider, sizeof(uislider_t));
+  uiWidgetLabelInit(&slider->label, &FONT_DEFAULT);
+  uiWidgetLabelSetText(&slider->label, label);
+  uiWidgetLabelInit(&slider->valueLabel, &FONT_DEFAULT);
+  slider->type = UI_SLIDER_TYPE_INT;
+  slider->min.i = min;
+  slider->max.i = max;
+  slider->step.i = step;
+  slider->value.i = mathClamp(value, min, max);
+  uiSliderRebuildValueLabel(slider);
+  uiSliderRebuildGeometry(slider);
+}
+
+float_t uiSliderGetFloat(const uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  return slider->type == UI_SLIDER_TYPE_INT ?
+    (float_t)slider->value.i : slider->value.f;
+}
+
+int32_t uiSliderGetInt(const uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  assertTrue(
+    slider->type == UI_SLIDER_TYPE_INT, "Slider is not an int slider"
+  );
+  return slider->value.i;
+}
+
+void uiSliderSetFloat(uislider_t *slider, const float_t value) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  assertTrue(
+    slider->type == UI_SLIDER_TYPE_FLOAT, "Slider is not a float slider"
+  );
+  slider->value.f = mathClamp(value, slider->min.f, slider->max.f);
+  uiSliderRebuildValueLabel(slider);
+  uiSliderRebuildGeometry(slider);
+}
+
+void uiSliderSetInt(uislider_t *slider, const int32_t value) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  assertTrue(
+    slider->type == UI_SLIDER_TYPE_INT, "Slider is not an int slider"
+  );
+  slider->value.i = mathClamp(value, slider->min.i, slider->max.i);
+  uiSliderRebuildValueLabel(slider);
+  uiSliderRebuildGeometry(slider);
+}
+
+void uiSliderStepUp(uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  if(slider->type == UI_SLIDER_TYPE_INT) {
+    int32_t next = slider->value.i + slider->step.i;
+    uiSliderSetInt(slider, next > slider->max.i ? slider->min.i : next);
+  } else {
+    float_t next = slider->value.f + slider->step.f;
+    uiSliderSetFloat(slider, next > slider->max.f ? slider->min.f : next);
+  }
+}
+
+void uiSliderStepDown(uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  if(slider->type == UI_SLIDER_TYPE_INT) {
+    int32_t next = slider->value.i - slider->step.i;
+    uiSliderSetInt(slider, next < slider->min.i ? slider->max.i : next);
+  } else {
+    float_t next = slider->value.f - slider->step.f;
+    uiSliderSetFloat(slider, next < slider->min.f ? slider->max.f : next);
+  }
+}
+
+float_t uiSliderGetRatio(const uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  if(slider->type == UI_SLIDER_TYPE_INT) {
+    if(slider->max.i == slider->min.i) return 0.0f;
+    return (float_t)(slider->value.i - slider->min.i) /
+      (float_t)(slider->max.i - slider->min.i);
+  }
+
+  if(slider->max.f == slider->min.f) return 0.0f;
+  return (slider->value.f - slider->min.f) / (slider->max.f - slider->min.f);
+}
+
+int32_t uiSliderGetStepCount(const uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  if(slider->type != UI_SLIDER_TYPE_INT || slider->step.i <= 0) return 0;
+  return (slider->max.i - slider->min.i) / slider->step.i;
+}
+
+bool_t uiSliderIsHighlighted(const uislider_t *slider) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  return slider->highlighted;
+}
+
+void uiSliderSetHighlighted(uislider_t *slider, const bool_t highlighted) {
+  assertNotNull(slider, "Slider cannot be NULL");
+  slider->highlighted = highlighted;
+  color_t color = highlighted ? COLOR_RED : COLOR_WHITE;
+  uiWidgetLabelSetColor(&slider->label, color);
+  uiWidgetLabelSetColor(&slider->valueLabel, color);
+}
+
+errorret_t uiSliderDraw(
+  const uislider_t *slider,
+  const float_t x,
+  const float_t y
+) {
+  assertNotNull(slider, "Slider cannot be NULL");
+
+  errorChain(uiWidgetLabelDraw(&slider->label, x, y));
+
+  shadermaterial_t trackMaterial = {
+    .unlit = {
+      .color = COLOR_DARK_GRAY,
+      .texture = &TEXTURE_WHITE
+    }
+  };
+  spritebatchsprite_t track = spriteBatchSpriteTranslate(
+    &slider->cachedTrack, x, y
+  );
+  errorChain(spriteBatchBuffer(&track, 1, &SHADER_UNLIT, trackMaterial));
+
+  if(slider->cachedFillVisible) {
+    shadermaterial_t fillMaterial = {
+      .unlit = {
+        .color = slider->highlighted ? COLOR_RED : COLOR_WHITE,
+        .texture = &TEXTURE_WHITE
+      }
+    };
+    spritebatchsprite_t fill = spriteBatchSpriteTranslate(
+      &slider->cachedFill, x, y
+    );
+    errorChain(spriteBatchBuffer(&fill, 1, &SHADER_UNLIT, fillMaterial));
+  }
+
+  if(slider->cachedMarkerCount > 0) {
+    spritebatchsprite_t markers[UI_SLIDER_STEP_MARKERS_MAX];
+    for(int32_t i = 0; i < slider->cachedMarkerCount; i++) {
+      markers[i] = spriteBatchSpriteTranslate(&slider->cachedMarkers[i], x, y);
+    }
+
+    shadermaterial_t markerMaterial = {
+      .unlit = {
+        .color = COLOR_WHITE,
+        .texture = &TEXTURE_WHITE
+      }
+    };
+    errorChain(spriteBatchBuffer(
+      markers, slider->cachedMarkerCount, &SHADER_UNLIT, markerMaterial
+    ));
+  }
+
+  errorChain(uiWidgetLabelDraw(
+    &slider->valueLabel,
+    x + slider->cachedTrack.max[0] + UI_SLIDER_GAP,
+    y
+  ));
+
+  errorOk();
+}
+
+void uiSliderRebuildValueLabel(uislider_t *slider) {
+  char_t valueText[UI_WIDGET_LABEL_TEXT_MAX];
+  if(slider->type == UI_SLIDER_TYPE_INT) {
+    stringFormat(
+      valueText, UI_WIDGET_LABEL_TEXT_MAX - 1, "%d", slider->value.i
+    );
+  } else {
+    stringFormat(
+      valueText, UI_WIDGET_LABEL_TEXT_MAX - 1, "%.2f", slider->value.f
+    );
+  }
+  uiWidgetLabelSetText(&slider->valueLabel, valueText);
+}
+
+void uiSliderRebuildGeometry(uislider_t *slider) {
+  int32_t labelW, labelH;
+  uiWidgetLabelGetSize(&slider->label, &labelW, &labelH);
+
+  float_t trackX = (float_t)labelW + UI_SLIDER_GAP;
+  float_t trackY = ((float_t)labelH - UI_SLIDER_TRACK_HEIGHT) * 0.5f;
+
+  slider->cachedTrack = (spritebatchsprite_t){
+    .min = { trackX, trackY, 0.0f },
+    .max = {
+      trackX + UI_SLIDER_TRACK_WIDTH, trackY + UI_SLIDER_TRACK_HEIGHT, 0.0f
+    },
+    .uvMin = { 0.0f, 0.0f },
+    .uvMax = { 1.0f, 1.0f }
+  };
+
+  float_t fillWidth = UI_SLIDER_TRACK_WIDTH * uiSliderGetRatio(slider);
+  slider->cachedFillVisible = fillWidth > 0.0f;
+  if(slider->cachedFillVisible) {
+    slider->cachedFill = (spritebatchsprite_t){
+      .min = { trackX, trackY, 0.0f },
+      .max = { trackX + fillWidth, trackY + UI_SLIDER_TRACK_HEIGHT, 0.0f },
+      .uvMin = { 0.0f, 0.0f },
+      .uvMax = { 1.0f, 1.0f }
+    };
+  }
+
+  int32_t stepCount = uiSliderGetStepCount(slider);
+  if(stepCount > 0 && stepCount < UI_SLIDER_STEP_MARKERS_MAX) {
+    for(int32_t i = 0; i <= stepCount; i++) {
+      float_t markerX = trackX +
+        UI_SLIDER_TRACK_WIDTH * (float_t)i / (float_t)stepCount;
+      slider->cachedMarkers[i] = (spritebatchsprite_t){
+        .min = {
+          markerX - UI_SLIDER_STEP_MARKER_WIDTH * 0.5f,
+          trackY - UI_SLIDER_STEP_MARKER_OVERHANG,
+          0.0f
+        },
+        .max = {
+          markerX + UI_SLIDER_STEP_MARKER_WIDTH * 0.5f,
+          trackY + UI_SLIDER_TRACK_HEIGHT + UI_SLIDER_STEP_MARKER_OVERHANG,
+          0.0f
+        },
+        .uvMin = { 0.0f, 0.0f },
+        .uvMax = { 1.0f, 1.0f }
+      };
+    }
+    slider->cachedMarkerCount = stepCount + 1;
+  } else {
+    slider->cachedMarkerCount = 0;
+  }
+}

archive/dusk/ui/widget/uislider.h

@@ -0,0 +1,215 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uiwidgetlabel.h"
+#include "display/spritebatch/spritebatchsprite.h"
+
+#define UI_SLIDER_TRACK_WIDTH 80.0f
+#define UI_SLIDER_TRACK_HEIGHT 4.0f
+#define UI_SLIDER_STEP_MARKER_WIDTH 2.0f
+#define UI_SLIDER_STEP_MARKER_OVERHANG 1.0f
+#define UI_SLIDER_GAP 4.0f
+
+/**
+ * Number of discrete steps below which an int slider renders individual
+ * step markers on its track instead of a smooth fill.
+ */
+#define UI_SLIDER_STEP_MARKERS_MAX 10
+
+typedef enum {
+  UI_SLIDER_TYPE_FLOAT,
+  UI_SLIDER_TYPE_INT,
+
+  UI_SLIDER_TYPE_COUNT
+} uislidertype_t;
+
+typedef union {
+  float_t f;
+  int32_t i;
+} uislidervalue_t;
+
+typedef struct {
+  uiwidgetlabel_t label;
+  uiwidgetlabel_t valueLabel;
+  uislidertype_t type;
+  uislidervalue_t value;
+  uislidervalue_t min;
+  uislidervalue_t max;
+  uislidervalue_t step;
+  bool_t highlighted;
+
+  // Track/fill/marker geometry, cached relative to origin (0,0) and only
+  // rebuilt when the value or step configuration changes (see
+  // uiSliderRebuildGeometry) -- uiSliderDraw just translates these into
+  // position instead of re-deriving them every frame.
+  spritebatchsprite_t cachedTrack;
+  spritebatchsprite_t cachedFill;
+  bool_t cachedFillVisible;
+  spritebatchsprite_t cachedMarkers[UI_SLIDER_STEP_MARKERS_MAX];
+  int32_t cachedMarkerCount;
+} uislider_t;
+
+/**
+ * Initializes a floating point slider.
+ *
+ * @param slider The slider to initialize.
+ * @param label Display label.
+ * @param value Initial value, clamped to [min, max].
+ * @param min Minimum value.
+ * @param max Maximum value.
+ * @param step The amount a single step moves the value by.
+ */
+void uiSliderInitFloat(
+  uislider_t *slider,
+  const char_t *label,
+  const float_t value,
+  const float_t min,
+  const float_t max,
+  const float_t step
+);
+
+/**
+ * Initializes an integer slider.
+ *
+ * @param slider The slider to initialize.
+ * @param label Display label.
+ * @param value Initial value, clamped to [min, max].
+ * @param min Minimum value.
+ * @param max Maximum value.
+ * @param step The amount a single step moves the value by.
+ */
+void uiSliderInitInt(
+  uislider_t *slider,
+  const char_t *label,
+  const int32_t value,
+  const int32_t min,
+  const int32_t max,
+  const int32_t step
+);
+
+/**
+ * Returns the slider's current value as a float. Works for both slider
+ * types; int values are widened to float.
+ *
+ * @param slider The slider to query.
+ * @returns The current value.
+ */
+float_t uiSliderGetFloat(const uislider_t *slider);
+
+/**
+ * Returns the slider's current value as an int. Only valid for
+ * UI_SLIDER_TYPE_INT sliders.
+ *
+ * @param slider The slider to query.
+ * @returns The current value.
+ */
+int32_t uiSliderGetInt(const uislider_t *slider);
+
+/**
+ * Sets the slider's value, clamped to [min, max]. Only valid for
+ * UI_SLIDER_TYPE_FLOAT sliders.
+ *
+ * @param slider The slider to update.
+ * @param value The new value.
+ */
+void uiSliderSetFloat(uislider_t *slider, const float_t value);
+
+/**
+ * Sets the slider's value, clamped to [min, max]. Only valid for
+ * UI_SLIDER_TYPE_INT sliders.
+ *
+ * @param slider The slider to update.
+ * @param value The new value.
+ */
+void uiSliderSetInt(uislider_t *slider, const int32_t value);
+
+/**
+ * Moves the slider's value up by one step, wrapping around to its min
+ * if the step would exceed its max.
+ *
+ * @param slider The slider to update.
+ */
+void uiSliderStepUp(uislider_t *slider);
+
+/**
+ * Moves the slider's value down by one step, wrapping around to its
+ * max if the step would go below its min.
+ *
+ * @param slider The slider to update.
+ */
+void uiSliderStepDown(uislider_t *slider);
+
+/**
+ * Returns the slider's current value normalized to a 0..1 range based
+ * on its min/max.
+ *
+ * @param slider The slider to query.
+ * @returns The normalized value.
+ */
+float_t uiSliderGetRatio(const uislider_t *slider);
+
+/**
+ * Returns the number of discrete steps between min and max. Always 0
+ * for float sliders.
+ *
+ * @param slider The slider to query.
+ * @returns The step count.
+ */
+int32_t uiSliderGetStepCount(const uislider_t *slider);
+
+/**
+ * Returns whether the slider is highlighted.
+ *
+ * @param slider The slider to query.
+ * @returns True if highlighted.
+ */
+bool_t uiSliderIsHighlighted(const uislider_t *slider);
+
+/**
+ * Sets the highlighted state of the slider.
+ *
+ * @param slider The slider to update.
+ * @param highlighted The new highlighted state.
+ */
+void uiSliderSetHighlighted(uislider_t *slider, const bool_t highlighted);
+
+/**
+ * Draws the slider at the given screen position: label, then track,
+ * then the current value as text. Int sliders with fewer than
+ * UI_SLIDER_STEP_MARKERS_MAX discrete steps render a marker per step
+ * instead of a plain track.
+ *
+ * @param slider The slider to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiSliderDraw(
+  const uislider_t *slider,
+  const float_t x,
+  const float_t y
+);
+
+/**
+ * Rebuilds the slider's cached value label from its current value.
+ * Called internally whenever value changes.
+ *
+ * @param slider The slider to update.
+ */
+void uiSliderRebuildValueLabel(uislider_t *slider);
+
+/**
+ * Rebuilds the slider's cached track/fill/marker geometry (relative to
+ * origin (0,0)) from its current label size, value, and step
+ * configuration. Called internally on init and whenever the value
+ * changes -- uiSliderDraw never recomputes this itself.
+ *
+ * @param slider The slider to update.
+ */
+void uiSliderRebuildGeometry(uislider_t *slider);

archive/dusk/ui/widget/uitab.c

@@ -0,0 +1,69 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uitab.h"
+#include "assert/assert.h"
+#include "display/text/text.h"
+#include "display/color.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/texture/texture.h"
+#include "display/shader/shaderunlit.h"
+
+void uiTabInit(uitab_t *tab, const char_t *label) {
+  assertNotNull(tab, "Tab cannot be NULL");
+  assertNotNull(label, "Label cannot be NULL");
+  uiWidgetLabelInit(&tab->label, &FONT_DEFAULT);
+  uiWidgetLabelSetText(&tab->label, label);
+  tab->active = false;
+  uiTabRebuildBackground(tab);
+}
+
+bool_t uiTabIsActive(const uitab_t *tab) {
+  assertNotNull(tab, "Tab cannot be NULL");
+  return tab->active;
+}
+
+void uiTabSetActive(uitab_t *tab, const bool_t active) {
+  assertNotNull(tab, "Tab cannot be NULL");
+  tab->active = active;
+}
+
+errorret_t uiTabDraw(
+  const uitab_t *tab,
+  const float_t x,
+  const float_t y
+) {
+  assertNotNull(tab, "Tab cannot be NULL");
+
+  spritebatchsprite_t sprite = spriteBatchSpriteTranslate(
+    &tab->cachedBackground, x, y
+  );
+  shadermaterial_t material = {
+    .unlit = {
+      .color = tab->active ? COLOR_GREEN : COLOR_RED,
+      .texture = &TEXTURE_WHITE
+    }
+  };
+  errorChain(spriteBatchBuffer(&sprite, 1, &SHADER_UNLIT, material));
+
+  errorChain(uiWidgetLabelDraw(&tab->label, x, y));
+
+  errorOk();
+}
+
+void uiTabRebuildBackground(uitab_t *tab) {
+  assertNotNull(tab, "Tab cannot be NULL");
+
+  int32_t labelW, labelH;
+  uiWidgetLabelGetSize(&tab->label, &labelW, &labelH);
+  tab->cachedBackground = (spritebatchsprite_t){
+    .min = { 0.0f, 0.0f, 0.0f },
+    .max = { (float_t)labelW, (float_t)labelH, 0.0f },
+    .uvMin = { 0.0f, 0.0f },
+    .uvMax = { 1.0f, 1.0f }
+  };
+}

archive/dusk/ui/widget/uitab.h

@@ -0,0 +1,70 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/widget/uiwidgetlabel.h"
+#include "display/spritebatch/spritebatchsprite.h"
+
+typedef struct {
+  uiwidgetlabel_t label;
+  bool_t active;
+
+  // Background quad, cached relative to origin (0,0) from the label's
+  // size at init -- uiTabDraw only translates this into position, since
+  // active/inactive only changes the material color, not the geometry.
+  spritebatchsprite_t cachedBackground;
+} uitab_t;
+
+/**
+ * Initializes a tab.
+ *
+ * @param tab The tab to initialize.
+ * @param label Display label.
+ */
+void uiTabInit(uitab_t *tab, const char_t *label);
+
+/**
+ * Returns whether the tab is active.
+ *
+ * @param tab The tab to query.
+ * @returns True if active.
+ */
+bool_t uiTabIsActive(const uitab_t *tab);
+
+/**
+ * Sets the active state of the tab.
+ *
+ * @param tab The tab to update.
+ * @param active The new active state.
+ */
+void uiTabSetActive(uitab_t *tab, const bool_t active);
+
+/**
+ * Draws the tab at the given screen position. Active tabs draw with a
+ * green background; inactive tabs draw with a red background.
+ *
+ * @param tab The tab to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiTabDraw(
+  const uitab_t *tab,
+  const float_t x,
+  const float_t y
+);
+
+/**
+ * Rebuilds the tab's cached background quad (relative to origin (0,0))
+ * from its current label size. Called internally by uiTabInit -- the
+ * background's geometry never changes afterwards, since the tab has no
+ * API to change its label text.
+ *
+ * @param tab The tab to update.
+ */
+void uiTabRebuildBackground(uitab_t *tab);

archive/dusk/ui/widget/uiwidgetlabel.c

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiwidgetlabel.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/string.h"
+#include "display/text/text.h"
+
+void uiWidgetLabelInit(uiwidgetlabel_t *label, font_t *font) {
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(font, "Font cannot be NULL");
+
+  memoryZero(label, sizeof(uiwidgetlabel_t));
+  label->font = font;
+  label->color = COLOR_WHITE;
+}
+
+void uiWidgetLabelSetText(uiwidgetlabel_t *label, const char_t *text) {
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(text, "Text cannot be NULL");
+  assertStrLenMax(text, UI_WIDGET_LABEL_TEXT_MAX, "Label text too long");
+
+  stringCopy(label->text, text, UI_WIDGET_LABEL_TEXT_MAX);
+  label->spriteCount = textBuildSpriteCache(
+    label->text, label->font, label->sprites,
+    UI_WIDGET_LABEL_SPRITE_COUNT_MAX, &label->width, &label->height
+  );
+}
+
+void uiWidgetLabelSetColor(uiwidgetlabel_t *label, const color_t color) {
+  assertNotNull(label, "Label cannot be NULL");
+  label->color = color;
+}
+
+void uiWidgetLabelGetSize(
+  const uiwidgetlabel_t *label,
+  int32_t *outWidth,
+  int32_t *outHeight
+) {
+  assertNotNull(label, "Label cannot be NULL");
+  assertNotNull(outWidth, "Output width cannot be NULL");
+  assertNotNull(outHeight, "Output height cannot be NULL");
+  *outWidth = label->width;
+  *outHeight = label->height;
+}
+
+errorret_t uiWidgetLabelDraw(
+  const uiwidgetlabel_t *label,
+  const float_t x,
+  const float_t y
+) {
+  assertNotNull(label, "Label cannot be NULL");
+  if(label->spriteCount == 0) errorOk();
+
+  spritebatchsprite_t scratch[UI_WIDGET_LABEL_SPRITE_COUNT_MAX];
+  errorChain(textDrawSpriteCache(
+    label->sprites, label->spriteCount, scratch, x, y, label->color,
+    label->font->texture
+  ));
+  errorOk();
+}

archive/dusk/ui/widget/uiwidgetlabel.h

@@ -0,0 +1,90 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "display/text/font.h"
+#include "display/spritebatch/spritebatchsprite.h"
+#include "display/color.h"
+
+// A cached, cheap-to-redraw label sized for embedding directly inside
+// small widgets (buttons, checkboxes, sliders, ...) rather than
+// referencing text by pointer and re-deriving glyph geometry every
+// frame. Capacity is intentionally much smaller than uilabel_t's -- it
+// gets embedded by value in every widget instance (and inside
+// uimenuitem_t's union, which is often arrayed), so keeping it small
+// matters on memory-constrained targets. See uilabel_t for the
+// general-purpose, larger-capacity equivalent.
+#define UI_WIDGET_LABEL_TEXT_MAX 64
+#define UI_WIDGET_LABEL_SPRITE_COUNT_MAX UI_WIDGET_LABEL_TEXT_MAX
+
+typedef struct {
+  char_t text[UI_WIDGET_LABEL_TEXT_MAX];
+  color_t color;
+  font_t *font;
+
+  spritebatchsprite_t sprites[UI_WIDGET_LABEL_SPRITE_COUNT_MAX];
+  uint32_t spriteCount;
+  int32_t width;
+  int32_t height;
+} uiwidgetlabel_t;
+
+/**
+ * Initializes a widget label, defaulting to white text and no text set.
+ *
+ * @param label The label to initialize.
+ * @param font Font to use for rendering. Must outlive the label.
+ */
+void uiWidgetLabelInit(uiwidgetlabel_t *label, font_t *font);
+
+/**
+ * Sets the label's text, rebuilding its cached sprites immediately.
+ * Call this whenever the displayed text changes -- uiWidgetLabelDraw
+ * never recomputes it.
+ *
+ * @param label The label to update.
+ * @param text Null-terminated string to display. Must be shorter than
+ * UI_WIDGET_LABEL_TEXT_MAX.
+ */
+void uiWidgetLabelSetText(uiwidgetlabel_t *label, const char_t *text);
+
+/**
+ * Sets the label's tint color. Cheap -- doesn't touch the sprite cache.
+ *
+ * @param label The label to update.
+ * @param color The new tint color.
+ */
+void uiWidgetLabelSetColor(uiwidgetlabel_t *label, const color_t color);
+
+/**
+ * Gets the measured size (in pixels) of the label's current text, cached
+ * from the last uiWidgetLabelSetText call.
+ *
+ * @param label The label to query.
+ * @param outWidth Pointer to store the width.
+ * @param outHeight Pointer to store the height.
+ */
+void uiWidgetLabelGetSize(
+  const uiwidgetlabel_t *label,
+  int32_t *outWidth,
+  int32_t *outHeight
+);
+
+/**
+ * Draws the label's cached sprites at the given screen position in a
+ * single batched buffer call. Does not recompute glyph layout.
+ *
+ * @param label The label to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @return Any error that occurs.
+ */
+errorret_t uiWidgetLabelDraw(
+  const uiwidgetlabel_t *label,
+  const float_t x,
+  const float_t y
+);

archive/duskrpg/ui/textbox/CMakeLists.txt

@@ -0,0 +1,10 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+target_sources(${DUSK_LIBRARY_TARGET_NAME}
+  PUBLIC
+    uitextbox.c
+    uitextboxmain.c
+)

archive/duskrpg/ui/textbox/uitextbox.c

@@ -0,0 +1,276 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uitextbox.h"
+#include "assert/assert.h"
+#include "util/memory.h"
+#include "util/string.h"
+#include "time/time.h"
+#include "display/text/text.h"
+#include "display/color.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+#include "ui/frame/uiframe.h"
+
+void uiTextboxInit(
+  uitextbox_t *box,
+  char_t *text,
+  const uint32_t maxLength,
+  uitextboxline_t *lines,
+  const uint32_t linesMax
+) {
+  assertNotNull(box, "Textbox cannot be NULL");
+  assertNotNull(text, "Text buffer cannot be NULL");
+  assertTrue(maxLength >= 1, "maxLength must be at least 1");
+  assertNotNull(lines, "Lines buffer cannot be NULL");
+  assertTrue(linesMax >= 1, "linesMax must be at least 1");
+  memoryZero(box, sizeof(uitextbox_t));
+  box->text = text;
+  box->maxLength = maxLength;
+  box->lines = lines;
+  box->linesMax = linesMax;
+  box->glyphsBuiltForPage = -1;
+}
+
+void uiTextboxSetText(uitextbox_t *box, const char_t *text) {
+  assertNotNull(box, "Textbox cannot be NULL");
+  assertNotNull(text, "Text cannot be NULL");
+  stringCopy(box->text, text, box->maxLength);
+  box->currentPage = 0;
+  box->scroll = 0;
+  box->layoutWidth = 0.0f;
+  box->layoutHeight = 0.0f;
+  box->glyphsBuiltForPage = -1;
+}
+
+void uiTextboxBuildLayout(
+  uitextbox_t *box,
+  const float_t width,
+  const float_t height
+) {
+  assertNotNull(box, "Textbox cannot be NULL");
+
+  box->glyphsBuiltForPage = -1;
+  box->layoutWidth = width;
+  box->layoutHeight = height;
+  box->lineCount = 0;
+  box->pageCount = 1;
+
+  float_t fontW = (float_t)FONT_DEFAULT.tileset->tileWidth;
+  float_t fontH = (float_t)FONT_DEFAULT.tileset->tileHeight;
+
+  if(fontW <= 0.0f || fontH <= 0.0f) return;
+
+  box->charsPerLine = (int32_t)(width / fontW);
+  box->linesPerPage = (int32_t)(height / (fontH + UI_TEXTBOX_LINE_SPACING));
+  if(box->linesPerPage > UI_TEXTBOX_LINES_PER_PAGE_MAX) {
+    box->linesPerPage = UI_TEXTBOX_LINES_PER_PAGE_MAX;
+  }
+
+  if(box->charsPerLine <= 0 || box->linesPerPage <= 0) return;
+  if(box->text[0] == '\0') return;
+
+  char_t *src = box->text;
+  int32_t i = 0;
+
+  while(src[i] != '\0' && box->lineCount < (int32_t)box->linesMax) {
+    if(src[i] == '\t') {
+      i++;
+      int32_t rem = box->lineCount % box->linesPerPage;
+      int32_t pad = rem > 0 ? box->linesPerPage - rem : 0;
+      while(pad > 0 && box->lineCount < (int32_t)box->linesMax) {
+        box->lines[box->lineCount].start = i;
+        box->lines[box->lineCount].count = 0;
+        box->lineCount++;
+        pad--;
+      }
+      continue;
+    }
+
+    int32_t lineStart = i;
+    int32_t lineWidth = 0;
+
+    while(src[i] != '\0') {
+      char_t c = src[i];
+
+      if(c == '\n') { i++; break; }
+      if(c == '\t') break;
+
+      if(c == ' ') {
+        int32_t wordLen = 0;
+        int32_t j = i + 1;
+        while(
+          src[j] != ' ' && src[j] != '\n' &&
+          src[j] != '\t' && src[j] != '\0'
+        ) {
+          wordLen++;
+          j++;
+        }
+
+        if(lineWidth > 0 && lineWidth + 1 + wordLen > box->charsPerLine) {
+          i++;
+          break;
+        }
+
+        lineWidth++;
+        i++;
+      } else {
+        if(lineWidth >= box->charsPerLine) break;
+        lineWidth++;
+        i++;
+      }
+    }
+
+    box->lines[box->lineCount].start = lineStart;
+    box->lines[box->lineCount].count = lineWidth;
+    box->lineCount++;
+  }
+
+  if(box->lineCount == 0) {
+    box->pageCount = 1;
+  } else {
+    box->pageCount =
+      (box->lineCount + box->linesPerPage - 1) / box->linesPerPage;
+  }
+}
+
+errorret_t uiTextboxUpdate(uitextbox_t *box) {
+  assertNotNull(box, "Textbox cannot be NULL");
+
+  #ifdef DUSK_TIME_DYNAMIC
+    if(TIME.dynamicUpdate) errorOk();
+  #endif
+
+  if(!uiTextboxPageIsComplete(box)) {
+    box->scroll += UI_TEXTBOX_SCROLL_CHARS_PER_TICK;
+  }
+
+  errorOk();
+}
+
+errorret_t uiTextboxDraw(
+  uitextbox_t *box,
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+) {
+  assertNotNull(box, "Textbox cannot be NULL");
+
+  float_t startX = (float_t)UI_FRAME_START_X;
+  float_t startY = (float_t)UI_FRAME_START_Y;
+  float_t contentX = x + startX;
+  float_t contentY = y + startY;
+  float_t contentW = width - 2.0f * startX;
+  float_t contentH = height - 2.0f * startY;
+
+  if(contentW != box->layoutWidth || contentH != box->layoutHeight) {
+    uiTextboxBuildLayout(box, contentW, contentH);
+  }
+
+  errorChain(uiFrameDrawCached(&box->frameCache, x, y, width, height));
+
+  if(box->lineCount == 0 || box->text[0] == '\0') errorOk();
+
+  if(box->glyphsBuiltForPage != box->currentPage) {
+    uiTextboxBuildPageGlyphs(box);
+  }
+
+  if(box->glyphCount == 0) errorOk();
+
+  int32_t visibleCount = 0;
+  while(
+    visibleCount < box->glyphCount &&
+    box->glyphs[visibleCount].revealAt <= box->scroll
+  ) visibleCount++;
+
+  if(visibleCount == 0) errorOk();
+
+  spritebatchsprite_t scratch[UI_TEXTBOX_PAGE_GLYPHS_MAX];
+  for(int32_t i = 0; i < visibleCount; i++) {
+    scratch[i] = spriteBatchSpriteTranslate(
+      &box->glyphs[i].sprite, contentX, contentY
+    );
+  }
+
+  shadermaterial_t material = {
+    .unlit = {
+      .color = COLOR_WHITE,
+      .texture = FONT_DEFAULT.texture
+    }
+  };
+  errorChain(spriteBatchBuffer(scratch, visibleCount, &SHADER_UNLIT, material));
+
+  errorOk();
+}
+
+void uiTextboxBuildPageGlyphs(uitextbox_t *box) {
+  assertNotNull(box, "Textbox cannot be NULL");
+
+  box->glyphCount = 0;
+
+  int32_t pageFirst = box->currentPage * box->linesPerPage;
+  int32_t pageLast = pageFirst + box->linesPerPage;
+  if(pageLast > box->lineCount) pageLast = box->lineCount;
+
+  float_t fontW = (float_t)FONT_DEFAULT.tileset->tileWidth;
+  float_t fontH = (float_t)FONT_DEFAULT.tileset->tileHeight;
+
+  int32_t consumed = 0;
+  for(int32_t li = pageFirst; li < pageLast; li++) {
+    uitextboxline_t *line = &box->lines[li];
+    float_t lineY =
+      (float_t)(li - pageFirst) * (fontH + UI_TEXTBOX_LINE_SPACING);
+
+    for(int32_t ci = 0; ci < line->count; ci++) {
+      consumed++;
+      char_t c = box->text[line->start + ci];
+      if(c == ' ') continue;
+
+      assertTrue(
+        box->glyphCount < UI_TEXTBOX_PAGE_GLYPHS_MAX,
+        "Textbox page produces too many glyphs"
+      );
+      uitextboxglyph_t *glyph = &box->glyphs[box->glyphCount++];
+      glyph->sprite = textGetSprite(
+        (vec2){ (float_t)ci * fontW, lineY }, c, &FONT_DEFAULT
+      );
+      glyph->revealAt = consumed;
+    }
+  }
+
+  box->glyphsBuiltForPage = box->currentPage;
+}
+
+int32_t uiTextboxGetPageCharCount(const uitextbox_t *box) {
+  assertNotNull(box, "Textbox cannot be NULL");
+  int32_t first = box->currentPage * box->linesPerPage;
+  int32_t last = first + box->linesPerPage;
+  if(last > box->lineCount) last = box->lineCount;
+  int32_t total = 0;
+  for(int32_t i = first; i < last; i++) {
+    total += box->lines[i].count;
+  }
+  return total;
+}
+
+bool_t uiTextboxPageIsComplete(const uitextbox_t *box) {
+  assertNotNull(box, "Textbox cannot be NULL");
+  return box->scroll >= uiTextboxGetPageCharCount(box);
+}
+
+bool_t uiTextboxHasNextPage(const uitextbox_t *box) {
+  assertNotNull(box, "Textbox cannot be NULL");
+  return box->currentPage + 1 < box->pageCount;
+}
+
+void uiTextboxNextPage(uitextbox_t *box) {
+  assertNotNull(box, "Textbox cannot be NULL");
+  if(!uiTextboxHasNextPage(box)) return;
+  box->currentPage++;
+  box->scroll = 0;
+}

archive/duskrpg/ui/textbox/uitextbox.h

@@ -0,0 +1,175 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "ui/frame/uiframe.h"
+#include "display/spritebatch/spritebatchsprite.h"
+
+#define UI_TEXTBOX_LINES_PER_PAGE_MAX 4
+#define UI_TEXTBOX_SCROLL_CHARS_PER_TICK 1
+#define UI_TEXTBOX_LINE_SPACING 0.0f
+
+// Fixed capacity for a page's cached glyph sprites (see uitextboxglyph_t).
+// Sized generously above UI_TEXTBOX_LINES_PER_PAGE_MAX worth of glyphs at
+// typical textbox widths; uiTextboxBuildPageGlyphs asserts if a page
+// somehow produces more than this.
+#define UI_TEXTBOX_PAGE_GLYPHS_MAX 512
+
+typedef struct {
+  int32_t start;
+  int32_t count;
+} uitextboxline_t;
+
+// A single visible glyph's cached sprite (relative to the textbox's
+// content origin, i.e. (0,0)) plus the scroll value at/after which it
+// becomes visible -- lets uiTextboxDraw turn the typewriter scroll into
+// a simple prefix-count instead of recomputing glyph geometry every
+// frame.
+typedef struct {
+  spritebatchsprite_t sprite;
+  int32_t revealAt;
+} uitextboxglyph_t;
+
+typedef struct {
+  char_t *text;
+  uint32_t maxLength;
+
+  uitextboxline_t *lines;
+  uint32_t linesMax;
+  int32_t lineCount;
+  int32_t charsPerLine;
+  int32_t linesPerPage;
+  int32_t pageCount;
+
+  // last dimensions used for layout; rebuild triggers when these change
+  float_t layoutWidth;
+  float_t layoutHeight;
+
+  int32_t currentPage;
+  int32_t scroll;
+
+  // Cached glyph sprites for the current page (see uitextboxglyph_t),
+  // rebuilt only when currentPage no longer matches
+  // glyphsBuiltForPage -- not every frame/scroll tick.
+  uitextboxglyph_t glyphs[UI_TEXTBOX_PAGE_GLYPHS_MAX];
+  int32_t glyphCount;
+  int32_t glyphsBuiltForPage;
+
+  uiframecache_t frameCache;
+} uitextbox_t;
+
+/**
+ * Initializes a textbox, zeroing all state and binding it to caller-owned
+ * text and line storage.
+ *
+ * @param box The textbox to initialize.
+ * @param text Caller-owned buffer the textbox copies its text into.
+ * @param maxLength Capacity of text, in characters.
+ * @param lines Caller-owned buffer the textbox lays lines out into.
+ * @param linesMax Capacity of lines, in entries.
+ */
+void uiTextboxInit(
+  uitextbox_t *box,
+  char_t *text,
+  const uint32_t maxLength,
+  uitextboxline_t *lines,
+  const uint32_t linesMax
+);
+
+/**
+ * Copies text into the textbox and marks layout as dirty.
+ * Resets currentPage and scroll to 0.
+ *
+ * @param box The textbox to update.
+ * @param text Null-terminated source string.
+ */
+void uiTextboxSetText(uitextbox_t *box, const char_t *text);
+
+/**
+ * Rebuilds word-wrap and page layout for the given draw dimensions.
+ * Called automatically by uiTextboxDraw when width or height changes.
+ *
+ * @param box The textbox to rebuild.
+ * @param width Available content width in pixels.
+ * @param height Available content height in pixels.
+ */
+void uiTextboxBuildLayout(
+  uitextbox_t *box,
+  const float_t width,
+  const float_t height
+);
+
+/**
+ * Advances the typewriter scroll by UI_TEXTBOX_SCROLL_CHARS_PER_TICK.
+ * Skipped on dynamic ticks.
+ *
+ * @param box The textbox to update.
+ * @returns Any error that occurs.
+ */
+errorret_t uiTextboxUpdate(uitextbox_t *box);
+
+/**
+ * Draws the textbox frame and visible text. Rebuilds layout automatically
+ * if width or height differs from the last draw call.
+ *
+ * @param box The textbox to draw.
+ * @param x Screen x position.
+ * @param y Screen y position.
+ * @param width Draw width in pixels.
+ * @param height Draw height in pixels.
+ * @returns Any error that occurs.
+ */
+errorret_t uiTextboxDraw(
+  uitextbox_t *box,
+  const float_t x,
+  const float_t y,
+  const float_t width,
+  const float_t height
+);
+
+/**
+ * Returns the total visible char count for the current page.
+ *
+ * @param box The textbox to query.
+ * @returns Total chars on the current page.
+ */
+int32_t uiTextboxGetPageCharCount(const uitextbox_t *box);
+
+/**
+ * Returns true when scroll has fully revealed the current page.
+ *
+ * @param box The textbox to query.
+ * @returns True if the current page is fully visible.
+ */
+bool_t uiTextboxPageIsComplete(const uitextbox_t *box);
+
+/**
+ * Returns true when there is at least one more page after the current one.
+ *
+ * @param box The textbox to query.
+ * @returns True if a next page exists.
+ */
+bool_t uiTextboxHasNextPage(const uitextbox_t *box);
+
+/**
+ * Advances to the next page and resets scroll to 0.
+ * Has no effect if already on the last page.
+ *
+ * @param box The textbox to advance.
+ */
+void uiTextboxNextPage(uitextbox_t *box);
+
+/**
+ * Rebuilds the cached glyph sprites (see uitextboxglyph_t) for the
+ * current page from its line layout. Called automatically by
+ * uiTextboxDraw whenever currentPage no longer matches the page the
+ * cache was last built for.
+ *
+ * @param box The textbox to rebuild.
+ */
+void uiTextboxBuildPageGlyphs(uitextbox_t *box);

archive/duskrpg/ui/textbox/uitextboxmain.c

@@ -0,0 +1,121 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uitextboxmain.h"
+#include "ui/focus/uifocus.h"
+#include "display/screen/screen.h"
+#include "display/text/text.h"
+#include "display/color.h"
+#include "display/spritebatch/spritebatch.h"
+#include "display/shader/shaderunlit.h"
+#include "ui/frame/uiframe.h"
+
+uitextboxmain_t UI_TEXTBOX_MAIN;
+static uifocusitem_t *focusItem = NULL;
+
+errorret_t uiTextboxMainInit(void) {
+  uiTextboxInit(
+    &UI_TEXTBOX_MAIN.box,
+    UI_TEXTBOX_MAIN.text, UI_TEXTBOX_MAIN_TEXT_MAX,
+    UI_TEXTBOX_MAIN.lines, UI_TEXTBOX_MAIN_LINES_MAX
+  );
+  errorOk();
+}
+
+void uiTextboxMainSetText(const char_t *text) {
+  uiTextboxSetText(&UI_TEXTBOX_MAIN.box, text);
+  if(focusItem != NULL) return;
+  focusItem = uiFocusPush(
+    1, 1,
+    uiTextboxMainFocusSelected,
+    NULL,
+    uiTextboxMainFocusClosed,
+    NULL,
+    NULL
+  );
+}
+
+errorret_t uiTextboxMainUpdate(void) {
+  if(focusItem == NULL) errorOk();
+  return uiTextboxUpdate(&UI_TEXTBOX_MAIN.box);
+}
+
+errorret_t uiTextboxMainDraw(void) {
+  if(focusItem == NULL) errorOk();
+  float_t fontH = (float_t)FONT_DEFAULT.tileset->tileHeight;
+  float_t h = (float_t)UI_TEXTBOX_MAIN_LINES * fontH +
+    (float_t)(UI_TEXTBOX_MAIN_LINES - 1) * UI_TEXTBOX_LINE_SPACING +
+    2.0f * (float_t)UI_FRAME_START_Y;
+  float_t w = (float_t)SCREEN.scanWidth;
+  float_t x = (float_t)SCREEN.scanX;
+  float_t y = (float_t)(SCREEN.scanY + SCREEN.scanHeight) - h;
+  errorChain(uiTextboxDraw(&UI_TEXTBOX_MAIN.box, x, y, w, h));
+
+  if(!uiTextboxPageIsComplete(&UI_TEXTBOX_MAIN.box)) errorOk();
+
+  float_t fontW = (float_t)FONT_DEFAULT.tileset->tileWidth;
+  float_t contentX = x + (float_t)UI_FRAME_START_X;
+  float_t contentY = y + (float_t)UI_FRAME_START_Y;
+  float_t contentW = w - 2.0f * (float_t)UI_FRAME_START_X;
+  float_t contentH = h - 2.0f * (float_t)UI_FRAME_START_Y;
+
+  shadermaterial_t material = {
+    .unlit = {
+      .color = COLOR_WHITE,
+      .texture = FONT_DEFAULT.texture
+    }
+  };
+
+  spritebatchsprite_t caret = textGetSprite(
+    (vec2){
+      contentX + contentW - fontW,
+      contentY + contentH - fontH
+    },
+    'v',
+    &FONT_DEFAULT
+  );
+  errorChain(spriteBatchBuffer(&caret, 1, &SHADER_UNLIT, material));
+
+  errorOk();
+}
+
+bool_t uiTextboxMainPageIsComplete(void) {
+  return uiTextboxPageIsComplete(&UI_TEXTBOX_MAIN.box);
+}
+
+bool_t uiTextboxMainHasNextPage(void) {
+  return uiTextboxHasNextPage(&UI_TEXTBOX_MAIN.box);
+}
+
+void uiTextboxMainNextPage(void) {
+  uiTextboxNextPage(&UI_TEXTBOX_MAIN.box);
+}
+
+bool_t uiTextboxMainIsActive(void) {
+  return focusItem != NULL;
+}
+
+bool_t uiTextboxMainFocusSelected(const uifocusitem_t *item) {
+  if(!uiTextboxPageIsComplete(&UI_TEXTBOX_MAIN.box)) {
+    UI_TEXTBOX_MAIN.box.scroll =
+      uiTextboxGetPageCharCount(&UI_TEXTBOX_MAIN.box);
+    return true;
+  }
+
+  if(uiTextboxHasNextPage(&UI_TEXTBOX_MAIN.box)) {
+    uiTextboxNextPage(&UI_TEXTBOX_MAIN.box);
+    return true;
+  }
+
+  uiFocusPopItem(focusItem);
+  return true;
+}
+
+bool_t uiTextboxMainFocusClosed(const uifocusitem_t *item) {
+  focusItem = NULL;
+  return true;
+}

archive/duskrpg/ui/textbox/uitextboxmain.h

@@ -0,0 +1,94 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "uitextbox.h"
+#include "ui/focus/uifocusitem.h"
+
+#define UI_TEXTBOX_MAIN_LINES 4
+#define UI_TEXTBOX_MAIN_TEXT_MAX 1024
+#define UI_TEXTBOX_MAIN_LINES_MAX 64
+
+typedef struct {
+  uitextbox_t box;
+  char_t text[UI_TEXTBOX_MAIN_TEXT_MAX];
+  uitextboxline_t lines[UI_TEXTBOX_MAIN_LINES_MAX];
+} uitextboxmain_t;
+
+extern uitextboxmain_t UI_TEXTBOX_MAIN;
+
+/**
+ * Initializes UI_TEXTBOX_MAIN.
+ *
+ * @returns Any error that occurs.
+ */
+errorret_t uiTextboxMainInit(void);
+
+/**
+ * Copies text into UI_TEXTBOX_MAIN and resets page and scroll.
+ *
+ * @param text Null-terminated source string.
+ */
+void uiTextboxMainSetText(const char_t *text);
+
+/**
+ * Advances the typewriter scroll for UI_TEXTBOX_MAIN.
+ *
+ * @returns Any error that occurs.
+ */
+errorret_t uiTextboxMainUpdate(void);
+
+/**
+ * Draws UI_TEXTBOX_MAIN full-width at the bottom of the screen.
+ * Position and size are derived from SCREEN each call.
+ *
+ * @returns Any error that occurs.
+ */
+errorret_t uiTextboxMainDraw(void);
+
+/**
+ * Returns true when the current page is fully scrolled in.
+ *
+ * @returns True if the current page is complete.
+ */
+bool_t uiTextboxMainPageIsComplete(void);
+
+/**
+ * Returns true when at least one more page follows the current one.
+ *
+ * @returns True if a next page exists.
+ */
+bool_t uiTextboxMainHasNextPage(void);
+
+/**
+ * Advances UI_TEXTBOX_MAIN to the next page and resets scroll.
+ * Has no effect if already on the last page.
+ */
+void uiTextboxMainNextPage(void);
+
+/**
+ * Returns true when UI_TEXTBOX_MAIN has focus (is visible and active).
+ *
+ * @returns True if the textbox is currently active.
+ */
+bool_t uiTextboxMainIsActive(void);
+
+/**
+ * Internal focus callback - skip scroll or advance page or dismiss.
+ *
+ * @param item The active focus item.
+ * @returns True.
+ */
+bool_t uiTextboxMainFocusSelected(const uifocusitem_t *item);
+
+/**
+ * Internal focus callback - clears the focus item pointer on dismiss.
+ *
+ * @param item The focus item being closed.
+ * @returns True.
+ */
+bool_t uiTextboxMainFocusClosed(const uifocusitem_t *item);

archive/duskrpg/ui/uitestlabel.c

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uitestlabel.h"
+#include "ui/widget/uilabel.h"
+#include "display/text/text.h"
+#include "display/screen/screen.h"
+#include "engine/engine.h"
+
+uilabel_t UI_TEST_LABEL;
+
+errorret_t uiTestLabelInit() {
+  uiLabelInit(&UI_TEST_LABEL, &FONT_DEFAULT);
+  uiLabelSetText(&UI_TEST_LABEL, "duskrpg");
+  errorOk();
+}
+
+errorret_t uiTestLabelDraw() {
+  int32_t versionWidth, versionHeight;
+  textMeasure(ENGINE.version, &FONT_DEFAULT, &versionWidth, &versionHeight);
+
+  errorChain(uiLabelDraw(
+    &UI_TEST_LABEL,
+    (float_t)(SCREEN.scanX + SCREEN.scanWidth - UI_TEST_LABEL.width),
+    (float_t)(
+      SCREEN.scanY + SCREEN.scanHeight - versionHeight -
+      UI_TEST_LABEL.height
+    )
+  ));
+  errorOk();
+}

archive/duskrpg/ui/uitestlabel.h

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+
+/**
+ * Initializes the test label, a smoke test for the duskrpg-side UI
+ * element extension point (uielementgame.h).
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiTestLabelInit();
+
+/**
+ * Draws the test label above the engine's debug version number.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiTestLabelDraw();

archive/test/ui/CMakeLists.txt

@@ -0,0 +1,11 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+include(dusktest)
+
+# Tests
+dusktest(test_uiframe.c)
+dusktest(test_uislider.c)
+dusktest(test_uitab.c)

archive/test/ui/test_uiframe.c

@@ -0,0 +1,68 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "dusktest.h"
+#include "ui/frame/uiframe.h"
+
+static void test_uiFrameBuildSprites_layout(void **state) {
+  UI_FRAME.tileset = (tileset_t){
+    .tileWidth = 1,
+    .tileHeight = 1,
+    .tileCount = 9,
+    .columns = 3,
+    .rows = 3,
+    .uv = { 0.25f, 0.25f }
+  };
+
+  const float_t x = 100.0f;
+  const float_t y = 50.0f;
+  const float_t width = 40.0f;
+  const float_t height = 30.0f;
+  const float_t tileW = (float_t)UI_FRAME_BORDER_WIDTH;
+  const float_t tileH = (float_t)UI_FRAME_BORDER_HEIGHT;
+
+  spritebatchsprite_t sprites[9];
+  uiFrameBuildSprites(sprites, x, y, width, height);
+
+  // Top-left corner sits exactly at the rect's origin.
+  assert_float_equal(sprites[0].min[0], x, 0.0001f);
+  assert_float_equal(sprites[0].min[1], y, 0.0001f);
+  assert_float_equal(sprites[0].max[0], x + tileW, 0.0001f);
+  assert_float_equal(sprites[0].max[1], y + tileH, 0.0001f);
+  assert_float_equal(sprites[0].uvMin[0], 0.0f, 0.0001f);
+  assert_float_equal(sprites[0].uvMin[1], 0.0f, 0.0001f);
+  assert_float_equal(sprites[0].uvMax[0], 0.25f, 0.0001f);
+  assert_float_equal(sprites[0].uvMax[1], 0.25f, 0.0001f);
+
+  // Top-middle edge stretches to fill the width minus both corners.
+  assert_float_equal(sprites[1].min[0], x + tileW, 0.0001f);
+  assert_float_equal(sprites[1].max[0], x + width - tileW, 0.0001f);
+  assert_float_equal(sprites[1].max[1], y + tileH, 0.0001f);
+
+  // Center tile fills the remaining interior on both axes.
+  assert_float_equal(sprites[4].min[0], x + tileW, 0.0001f);
+  assert_float_equal(sprites[4].min[1], y + tileH, 0.0001f);
+  assert_float_equal(sprites[4].max[0], x + width - tileW, 0.0001f);
+  assert_float_equal(sprites[4].max[1], y + height - tileH, 0.0001f);
+
+  // Bottom-right corner sits exactly at the rect's far corner, sampling
+  // tileset column 2, row 2.
+  assert_float_equal(sprites[8].min[0], x + width - tileW, 0.0001f);
+  assert_float_equal(sprites[8].min[1], y + height - tileH, 0.0001f);
+  assert_float_equal(sprites[8].max[0], x + width, 0.0001f);
+  assert_float_equal(sprites[8].max[1], y + height, 0.0001f);
+  assert_float_equal(sprites[8].uvMin[0], 0.5f, 0.0001f);
+  assert_float_equal(sprites[8].uvMin[1], 0.5f, 0.0001f);
+}
+
+int main(int argc, char **argv) {
+  const struct CMUnitTest tests[] = {
+    cmocka_unit_test(test_uiFrameBuildSprites_layout),
+  };
+
+  return cmocka_run_group_tests(tests, NULL, NULL);
+}

archive/test/ui/test_uislider.c

@@ -0,0 +1,114 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "dusktest.h"
+#include "ui/widget/uislider.h"
+#include "util/memory.h"
+
+// uiSliderInitFloat/InitInt require a real font (FONT_DEFAULT) to build
+// the label's glyph cache, which needs a live GL context this test binary
+// doesn't have -- see the label size caching contract for why this is
+// safe to bypass here (uiSliderRebuildGeometry only reads slider->label's
+// already-measured width/height, it never touches the font itself).
+static void sliderSetupFloat(
+  uislider_t *slider,
+  const float_t value,
+  const float_t min,
+  const float_t max,
+  const float_t step
+) {
+  memoryZero(slider, sizeof(uislider_t));
+  slider->label.width = 20;
+  slider->label.height = 10;
+  slider->type = UI_SLIDER_TYPE_FLOAT;
+  slider->min.f = min;
+  slider->max.f = max;
+  slider->step.f = step;
+  slider->value.f = value;
+}
+
+static void sliderSetupInt(
+  uislider_t *slider,
+  const int32_t value,
+  const int32_t min,
+  const int32_t max,
+  const int32_t step
+) {
+  memoryZero(slider, sizeof(uislider_t));
+  slider->label.width = 20;
+  slider->label.height = 10;
+  slider->type = UI_SLIDER_TYPE_INT;
+  slider->min.i = min;
+  slider->max.i = max;
+  slider->step.i = step;
+  slider->value.i = value;
+}
+
+static void test_uiSliderRebuildGeometry_trackPosition(void **state) {
+  uislider_t slider;
+  sliderSetupFloat(&slider, 0.0f, 0.0f, 1.0f, 0.1f);
+  uiSliderRebuildGeometry(&slider);
+
+  const float_t expectedX = (float_t)slider.label.width + UI_SLIDER_GAP;
+  const float_t expectedY =
+    ((float_t)slider.label.height - UI_SLIDER_TRACK_HEIGHT) * 0.5f;
+
+  assert_float_equal(slider.cachedTrack.min[0], expectedX, 0.0001f);
+  assert_float_equal(slider.cachedTrack.min[1], expectedY, 0.0001f);
+  assert_float_equal(
+    slider.cachedTrack.max[0], expectedX + UI_SLIDER_TRACK_WIDTH, 0.0001f
+  );
+}
+
+static void test_uiSliderRebuildGeometry_fillVisibility(void **state) {
+  uislider_t slider;
+
+  // At the minimum value, the ratio is 0 -- no fill should be visible.
+  sliderSetupFloat(&slider, 0.0f, 0.0f, 10.0f, 1.0f);
+  uiSliderRebuildGeometry(&slider);
+  assert_false(slider.cachedFillVisible);
+
+  // Halfway to max -- fill should cover half the track.
+  sliderSetupFloat(&slider, 5.0f, 0.0f, 10.0f, 1.0f);
+  uiSliderRebuildGeometry(&slider);
+  assert_true(slider.cachedFillVisible);
+  assert_float_equal(
+    slider.cachedFill.max[0] - slider.cachedFill.min[0],
+    UI_SLIDER_TRACK_WIDTH * 0.5f,
+    0.0001f
+  );
+}
+
+static void test_uiSliderRebuildGeometry_stepMarkers(void **state) {
+  uislider_t slider;
+
+  // 5 steps between 0 and 10 -- under the marker cap, so markers render.
+  sliderSetupInt(&slider, 0, 0, 10, 2);
+  uiSliderRebuildGeometry(&slider);
+  assert_int_equal(slider.cachedMarkerCount, 6);
+  assert_float_equal(
+    slider.cachedMarkers[0].min[0], slider.cachedTrack.min[0] -
+      UI_SLIDER_STEP_MARKER_WIDTH * 0.5f,
+    0.0001f
+  );
+
+  // 100 steps -- over the marker cap, so it falls back to a smooth fill
+  // with no markers.
+  sliderSetupInt(&slider, 0, 0, 100, 1);
+  uiSliderRebuildGeometry(&slider);
+  assert_int_equal(slider.cachedMarkerCount, 0);
+}
+
+int main(int argc, char **argv) {
+  const struct CMUnitTest tests[] = {
+    cmocka_unit_test(test_uiSliderRebuildGeometry_trackPosition),
+    cmocka_unit_test(test_uiSliderRebuildGeometry_fillVisibility),
+    cmocka_unit_test(test_uiSliderRebuildGeometry_stepMarkers),
+  };
+
+  return cmocka_run_group_tests(tests, NULL, NULL);
+}

archive/test/ui/test_uitab.c

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "dusktest.h"
+#include "ui/widget/uitab.h"
+#include "util/memory.h"
+
+// uiTabInit requires a real font (FONT_DEFAULT) to build the label's
+// glyph cache, which needs a live GL context this test binary doesn't
+// have. uiTabRebuildBackground only reads the label's already-measured
+// width/height, so it's safe to set those directly and exercise it here.
+static void test_uiTabRebuildBackground_matchesLabelSize(void **state) {
+  uitab_t tab;
+  memoryZero(&tab, sizeof(uitab_t));
+  tab.label.width = 42;
+  tab.label.height = 12;
+
+  uiTabRebuildBackground(&tab);
+
+  assert_float_equal(tab.cachedBackground.min[0], 0.0f, 0.0001f);
+  assert_float_equal(tab.cachedBackground.min[1], 0.0f, 0.0001f);
+  assert_float_equal(tab.cachedBackground.max[0], 42.0f, 0.0001f);
+  assert_float_equal(tab.cachedBackground.max[1], 12.0f, 0.0001f);
+}
+
+int main(int argc, char **argv) {
+  const struct CMUnitTest tests[] = {
+    cmocka_unit_test(test_uiTabRebuildBackground_matchesLabelSize),
+  };
+
+  return cmocka_run_group_tests(tests, NULL, NULL);
+}