CompressedTextures example fails assertion in Metal

[certik]

When running the CompressedTextures example on macOS, in the build directory:

$ make && ./SDL_gpu_examples
[...]
[  2%] Building C object CMakeFiles/SDL_gpu_examples.dir/Examples/CompressedTextures.c.o
[  5%] Linking C executable SDL_gpu_examples
[100%] Built target SDL_gpu_examples
2025-10-25 17:17:03.232 SDL_gpu_examples[20138:33017644] Welcome to the SDL_GPU example suite!
2025-10-25 17:17:03.232 SDL_gpu_examples[20138:33017644] Press A/D (or LB/RB) to move between examples!
2025-10-25 17:17:03.238 SDL_gpu_examples[20138:33017644] STARTING EXAMPLE: ClearScreen
2025-10-25 17:17:03.239 SDL_gpu_examples[20138:33017644] Metal API Validation Enabled
2025-10-25 17:17:07.601 SDL_gpu_examples[20138:33017644] STARTING EXAMPLE: CompressedTextures
-[MTLDebugBlitCommandEncoder validateCopyFromBuffer:sourceOffset:sourceBytesPerRow:sourceBytesPerImage:sourceSize:toTexture:destinationSlice:destinationLevel:destinationOrigin:options:]:806: failed assertion `Copy From Buffer Validation
totalBytesUsed(17888) must be <= [sourceBuffer length](16384).
'

This can be fixed by:

--- a/Examples/CompressedTextures.c
+++ b/Examples/CompressedTextures.c
@@ -1,7 +1,7 @@
 #include "Common.h"

 #define BC_IMAGE_COUNT 12
-#define ASTC_IMAGE_COUNT 14
+#define ASTC_IMAGE_COUNT 13

 static SDL_GPUTexture* SrcTextures[BC_IMAGE_COUNT + ASTC_IMAGE_COUNT];
 static SDL_GPUTexture* DstTextures[BC_IMAGE_COUNT + ASTC_IMAGE_COUNT];
@@ -32,7 +32,7 @@ static SDL_GPUTextureFormat TextureFormats[BC_IMAGE_COUNT + ASTC_IMAGE_COUNT] =
        SDL_GPU_TEXTUREFORMAT_ASTC_8x6_UNORM,
        SDL_GPU_TEXTUREFORMAT_ASTC_8x8_UNORM,
        SDL_GPU_TEXTUREFORMAT_ASTC_10x5_UNORM,
-       SDL_GPU_TEXTUREFORMAT_ASTC_10x6_UNORM,
+       //SDL_GPU_TEXTUREFORMAT_ASTC_10x6_UNORM,
        SDL_GPU_TEXTUREFORMAT_ASTC_10x8_UNORM,
        SDL_GPU_TEXTUREFORMAT_ASTC_10x10_UNORM,
        SDL_GPU_TEXTUREFORMAT_ASTC_12x10_UNORM,

Probably the image size returned by the ASTC reader is incorrect for this particular case.

With this workaround every example works.