Simplify uilabel to caller-owned buffers

uilabel no longer owns fixed-size text/sprite arrays or copies text
internally - callers pass in their own buffers and write text
directly, then mark the label dirty. This drops SetText/GetText and
the textMax bound in favor of a single Rebuffer entry point, and lets
widgets like uibutton alias an existing (possibly immutable) label
string instead of duplicating it.

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

src/dusk/ui/widget/uilabel.c

@@ -6,25 +6,25 @@
  */
 
 #include "uilabel.h"
+#include "assert/assert.h"
 #include "util/memory.h"
-#include "util/string.h"
 #include "display/text/text.h"
 #include "display/spritebatch/spritebatch.h"
 #include "display/shader/shaderunlit.h"
 
-void uiLabelInit(uilabel_t *label, const char_t *text) {
+void uiLabelInit(
+  uilabel_t *label,
+  const char_t *text,
+  spritebatchsprite_t *sprites,
+  const int32_t spritesMax
+) {
+  assertNotNull(text, "Text buffer cannot be NULL");
+  assertNotNull(sprites, "Sprites buffer cannot be NULL");
+
   memoryZero(label, sizeof(uilabel_t));
-  uiLabelSetText(label, text);
-}
-
-void uiLabelSetText(uilabel_t *label, const char_t *text) {
-  if(stringCompare(label->text, text) == 0) return;
-  stringCopy(label->text, text, UI_LABEL_TEXT_MAX);
-  label->dirty = true;
-}
-
-const char_t * uiLabelGetText(const uilabel_t *label) {
-  return label->text;
+  label->text = text;
+  label->sprites = sprites;
+  label->spritesMax = spritesMax;
 }
 
 void uiLabelSetX(uilabel_t *label, const float_t x) {
@@ -49,6 +49,19 @@ float_t uiLabelGetY(const uilabel_t *label) {
 
 void uiLabelRebuffer(uilabel_t *label) {
   if(!label->dirty) return;
+
+  textMeasure(label->text, &FONT_DEFAULT, &label->width, &label->height);
+
+  int32_t charIndex = 0;
+  float_t posX = label->x;
+  float_t posY = label->y;
+  label->spriteCount = textBuffer(
+    label->x, label->y, label->text, &FONT_DEFAULT,
+    label->sprites, label->spritesMax,
+    &charIndex, &posX, &posY
+  );
+
+  label->dirty = false;
 }
 
 errorret_t uiLabelRender(uilabel_t *label, const color_t color) {
@@ -62,7 +75,7 @@ errorret_t uiLabelRender(uilabel_t *label, const color_t color) {
     }
   };
   errorChain(spriteBatchBuffer(
-    label->buffer, label->spriteCount, &SHADER_UNLIT, material
+    label->sprites, label->spriteCount, &SHADER_UNLIT, material
   ));
 
   errorOk();

src/dusk/ui/widget/uilabel.h

@@ -10,12 +10,10 @@
 #include "display/spritebatch/spritebatchsprite.h"
 #include "display/color.h"
 
-#define UI_LABEL_TEXT_MAX 128
-
 typedef struct {
-  char_t text[UI_LABEL_TEXT_MAX];
-  spritebatchsprite_t sprites[UI_LABEL_TEXT_MAX];
-  spritebatchsprite_t buffer[UI_LABEL_TEXT_MAX];
+  const char_t *text;
+  spritebatchsprite_t *sprites;
+  int32_t spritesMax;
   uint32_t spriteCount;
   int32_t width;
   int32_t height;
@@ -25,28 +23,23 @@ typedef struct {
 } uilabel_t;
 
 /**
- * Initializes a label.
+ * Initializes a label. The caller owns the text buffer and writes its
+ * contents directly (setting label->dirty afterwards); call
+ * uiLabelRebuffer or uiLabelRender to rebuild the cached sprites.
  *
  * @param label The label to initialize.
- * @param text Display text; copied internally, safe to be transient.
+ * @param text Caller-owned, null-terminated string the label reads from
+ * directly; never written to by the label. Cannot be NULL.
+ * @param sprites Caller-owned sprite buffer the label writes cached
+ * glyph sprites into. Cannot be NULL.
+ * @param spritesMax Number of sprites the sprites buffer can hold.
  */
-void uiLabelInit(uilabel_t *label, const char_t *text);
-
-/**
- * Sets the display text of the label, rebuilding its cached sprites.
- *
- * @param label The label to update.
- * @param text Display text; copied internally, safe to be transient.
- */
-void uiLabelSetText(uilabel_t *label, const char_t *text);
-
-/**
- * Returns the display text of the label.
- *
- * @param label The label to query.
- * @returns The label's text.
- */
-const char_t * uiLabelGetText(const uilabel_t *label);
+void uiLabelInit(
+  uilabel_t *label,
+  const char_t *text,
+  spritebatchsprite_t *sprites,
+  const int32_t spritesMax
+);
 
 /**
  * Sets the screen x position of the label.
@@ -81,10 +74,9 @@ void uiLabelSetY(uilabel_t *label, const float_t y);
 float_t uiLabelGetY(const uilabel_t *label);
 
 /**
- * Rebuffers the label: rebuilds its cached local-space sprites if the
- * text has changed, then re-translates them into its render buffer at
- * its current x/y position. Called internally by uiLabelRender when
- * either dirty flag is set.
+ * Rebuffers the label's cached sprites from its current text at its
+ * current x/y position. No-op unless the label is dirty. Called
+ * internally by uiLabelRender.
  *
  * @param label The label to rebuffer.
  */