Add autosave system with forced no-save-device prompt on failure

autoSaveQueue() is a single callable entry point for requesting an
autosave; autoSaveUpdate() pumps the queue each frame and, if the write
fails (e.g. no memory card), forces the existing no-card modal back
open and pauses world simulation until the player retries or accepts a
temporary session. A small overlay shows "SAVING" while a write is in
flight.

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

src/dusk/engine/engine.c

@@ -20,6 +20,7 @@
 #include "system/system.h"
 #include "console/console.h"
 #include "save/save.h"
+#include "save/autosave.h"
 
 engine_t ENGINE;
 
@@ -54,7 +55,6 @@ errorret_t engineInit(const int32_t argc, const char_t **argv) {
   #endif
 
   sceneSet(SCENE_TYPE_INITIAL);
-  
 
   errorOk();
 }
@@ -63,6 +63,7 @@ errorret_t engineUpdate(void) {
   // Order here is important.
   errorChain(networkUpdate());
   errorChain(saveUpdate());
+  autoSaveUpdate();
   timeUpdate();
   inputUpdate();
   consoleUpdate();

src/dusk/rpg/rpg.c

@@ -18,6 +18,7 @@
 #include "util/memory.h"
 #include "assert/assert.h"
 #include "save/save.h"
+#include "save/autosave.h"
 #include "error/error.h"
 #include "scene/scene.h"
 
@@ -78,6 +79,12 @@ errorret_t rpgUpdate(void) {
     }
   #endif
 
+  // A failed autosave forces a no-save-device prompt (see autosave.h) -
+  // freeze the world entirely until the player resolves it, rather than
+  // letting NPCs/cutscenes/camera keep running behind a modal that's
+  // supposed to be blocking.
+  if(autoSaveIsBlocking()) errorOk();
+
   // TODO: Do not update if the scene is not the map scene?
   errorChain(mapUpdate());
 

src/dusk/save/CMakeLists.txt

@@ -8,4 +8,5 @@ target_sources(${DUSK_LIBRARY_TARGET_NAME}
   PUBLIC
     save.c
     savestream.c
+    autosave.c
 )

src/dusk/save/autosave.c

@@ -0,0 +1,72 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "autosave.h"
+#include "save.h"
+#include "error/error.h"
+#include "ui/frame/initial/uiinitialnocard.h"
+
+autosave_t AUTO_SAVE;
+
+static void autoSaveNoCardResult(const bool_t retry, void *user) {
+  AUTO_SAVE.blocking = false;
+
+  // "Retry" just re-queues the write for the next tick - there's no way
+  // to force a re-probe of the hardware mid-session (see saveInit()'s doc
+  // comment), so this only actually helps for a transient failure.
+  if(retry) {
+    AUTO_SAVE.pending = true;
+    return;
+  }
+
+  // The player explicitly acknowledged there's no save device and chose
+  // to proceed anyway - sticks for the rest of the session, so future
+  // autoSaveUpdate() calls silently skip instead of prompting again.
+  saveMarkTemporary();
+}
+
+static void autoSaveWriteComplete(errorret_t result, void *user) {
+  AUTO_SAVE.saving = false;
+  if(errorIsOk(result)) return;
+
+  errorCatch(errorPrint(result));
+
+  // The write failed - most likely no save medium is present right now
+  // (a GameCube with no memory card inserted, for example). Pause world
+  // simulation and force the same prompt the initial boot scene uses so
+  // the player can insert a card and retry, or explicitly accept a
+  // temporary, unsaved session.
+  AUTO_SAVE.blocking = true;
+  uiInitialNoCardOpen(autoSaveNoCardResult, NULL);
+}
+
+void autoSaveQueue(void) {
+  AUTO_SAVE.pending = true;
+}
+
+void autoSaveUpdate(void) {
+  if(AUTO_SAVE.blocking) return;
+  if(!AUTO_SAVE.pending) return;
+  if(saveIsBusy()) return;
+
+  AUTO_SAVE.pending = false;
+
+  // Already opted out of saving for this session - nothing to do, and
+  // definitely don't reprompt every time an autosave is queued.
+  if(saveIsTemporary()) return;
+
+  AUTO_SAVE.saving = true;
+  saveWriteSlot(SAVE_ACTIVE_SLOT, autoSaveWriteComplete, NULL);
+}
+
+bool_t autoSaveIsSaving(void) {
+  return AUTO_SAVE.saving;
+}
+
+bool_t autoSaveIsBlocking(void) {
+  return AUTO_SAVE.blocking;
+}

src/dusk/save/autosave.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 "error/error.h"
+
+typedef struct {
+  /** True from autoSaveQueue() until the queued write starts. */
+  bool_t pending;
+  /** True while the queued write is actually in flight. */
+  bool_t saving;
+  /**
+   * True while the forced no-save-device prompt is up after a queued
+   * write failed - see autoSaveUpdate(). World simulation must pause
+   * while this is true (see rpgUpdate()).
+   */
+  bool_t blocking;
+} autosave_t;
+
+extern autosave_t AUTO_SAVE;
+
+/**
+ * Queues an autosave to run on a future engine tick. Safe to call as
+ * often as needed (e.g. after every map transition or story event) -
+ * repeated calls before the queued save starts just collapse into one.
+ */
+void autoSaveQueue(void);
+
+/**
+ * Pumps the queued autosave: starts the write once nothing else is
+ * using the save system, and if that write fails (e.g. a GameCube with
+ * no memory card inserted), forces the same no-save-device prompt the
+ * initial boot scene uses and pauses world simulation until the player
+ * resolves it. Must be called every engine frame, after saveUpdate().
+ */
+void autoSaveUpdate(void);
+
+/**
+ * True while a queued autosave's write is actually in progress. Intended
+ * for UI to show a "Saving" indicator.
+ *
+ * @return true if an autosave write is currently in flight.
+ */
+bool_t autoSaveIsSaving(void);
+
+/**
+ * True while a failed autosave is forcing the no-save-device prompt and
+ * waiting on the player's decision. Intended for the world simulation to
+ * pause while this is true.
+ *
+ * @return true if an autosave is currently blocking on player input.
+ */
+bool_t autoSaveIsBlocking(void);

src/dusk/ui/overlay/CMakeLists.txt

@@ -8,4 +8,5 @@ target_sources(${DUSK_LIBRARY_TARGET_NAME}
     uicrop.c
     uifullbox.c
     uiloading.c
+    uiautosave.c
 )

src/dusk/ui/overlay/uiautosave.c

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "uiautosave.h"
+#include "save/autosave.h"
+#include "display/text/text.h"
+#include "display/screen/screen.h"
+#include "display/spritebatch/spritebatch.h"
+
+// TODO: Localize once this grows beyond a placeholder indicator.
+#define UI_AUTOSAVE_TEXT "SAVING"
+
+errorret_t uiAutoSaveDraw(void) {
+  if(!autoSaveIsSaving()) errorOk();
+
+  int32_t textW, textH;
+  textMeasure(UI_AUTOSAVE_TEXT, &FONT_DEFAULT, &textW, &textH);
+
+  float_t x = (float_t)SCREEN.scanX + UI_AUTOSAVE_MARGIN;
+  float_t y = (float_t)(SCREEN.scanY + SCREEN.scanHeight) -
+    (float_t)textH - UI_AUTOSAVE_MARGIN;
+
+  errorChain(textDraw(x, y, UI_AUTOSAVE_TEXT, COLOR_WHITE, &FONT_DEFAULT));
+  return spriteBatchFlush();
+}

src/dusk/ui/overlay/uiautosave.h

@@ -0,0 +1,20 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+
+#define UI_AUTOSAVE_MARGIN 8.0f
+
+/**
+ * Draws a "Saving" indicator in the bottom-left corner of the screen
+ * while an autosave write is in flight (see save/autosave.h). No-op
+ * otherwise.
+ *
+ * @return Any error that occurs.
+ */
+errorret_t uiAutoSaveDraw(void);

src/dusk/ui/uielement.c

@@ -12,6 +12,7 @@
 #include "engine/engine.h"
 #include "ui/overlay/uifullbox.h"
 #include "ui/overlay/uiloading.h"
+#include "ui/overlay/uiautosave.h"
 #include "ui/debug/uiplayerpos.h"
 #include "ui/overlay/uicrop.h"
 #include "ui/transition/uitransition.h"
@@ -129,11 +130,13 @@ uielement_t UI_ELEMENTS[] = {
     .draw = uiCropDraw
   },
 
+  { .draw = uiAutoSaveDraw },
+
   // Debug items
   { .draw = uiConsoleDraw },
   { .draw = uiFPSDraw },
   { .draw = uiPlayerPosDraw },
-  
+
   { 0 } // Null terminator
 };