Cache transform buffer to avoid per-frame malloc

[jserv]

This implements transform buffer cache in twin_pixmap_t to eliminate malloc and free on every transform compositing operation. Previous code allocated and freed the xform buffer for each transformation, creating unnecessary allocation overhead in the render loop.

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Summary by cubic

Cached the transform buffer in twin_pixmap_t to stop per-frame malloc/free during compositing. This reduces allocation overhead in the render loop and should improve frame stability.

• Refactors
  • Added xform_cache and xform_cache_size to twin_pixmap_t.
  • Reuse or grow the cached buffer in twin_pixmap_init_xform; twin_pixmap_free_xform is now a no-op.
  • Initialize cache in pixmap_create and pixmap_create_const; free it in twin_pixmap_destroy.

[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="include/twin.h">

<violation number="1" location="include/twin.h:259">
`xform_cache_size` is stored in a 16-bit `twin_coord_t`, so large transform buffers overflow the cached size and lead to undersized allocations; please store this size in a wider type (e.g., size_t) and adjust the related calculations.</violation>
</file>

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[cubic-dev-ai]

xform_cache_size is stored in a 16-bit twin_coord_t, so large transform buffers overflow the cached size and lead to undersized allocations; please store this size in a wider type (e.g., size_t) and adjust the related calculations.

Prompt for AI agents

Address the following comment on include/twin.h at line 259:

<comment>`xform_cache_size` is stored in a 16-bit `twin_coord_t`, so large transform buffers overflow the cached size and lead to undersized allocations; please store this size in a wider type (e.g., size_t) and adjust the related calculations.</comment>

<file context>
@@ -253,6 +253,10 @@ typedef struct _twin_pixmap {
+
+    /* Transform buffer cache for compositing operations */
+    void *xform_cache;             /**&lt; Cached xform buffer */
+    twin_coord_t xform_cache_size; /**&lt; Cached xform buffer size in bytes */
 } twin_pixmap_t;
 
</file context>

✅ Addressed in 3a21d01