Describe tight-packing of image-copy ops, including depth/stencil

kainino0x · kainino0x · commit 189c73a45d2f · 2021-11-19T17:13:58.000-08:00
Fixes #652
diff --git a/spec/index.bs b/spec/index.bs
@@ -5983,6 +5983,11 @@ dictionary GPUImageCopyExternalImage {
 WebGPU provides {{GPUCommandEncoder/copyBufferToTexture()}} for buffer-to-texture copies and
 {{GPUCommandEncoder/copyTextureToBuffer()}} for texture-to-buffer copies.
 
+Pixels are tightly-packed in the linear-memory layout of each row of an image copy.
+This includes [[#depth-formats|copies to/from specific aspects of depth/stencil textures]]:
+stencil values are tightly packed in an array of bytes;
+depth values are tightly packed in an array of the appropriate type ("depth16unorm" or "depth32float").
+
 The following definitions and validation rules apply to both {{GPUCommandEncoder/copyBufferToTexture()}}
 and {{GPUCommandEncoder/copyTextureToBuffer()}}.
 
@@ -9960,7 +9965,8 @@ and {{GPUTextureUsage/STORAGE_BINDING|GPUTextureUsage.STORAGE_BINDING}} usage re
 
 ### Depth/stencil formats ### {#depth-formats}
 
-All depth formats support {{GPUTextureUsage/COPY_SRC}}, {{GPUTextureUsage/COPY_DST}}, {{GPUTextureUsage/TEXTURE_BINDING}}, and {{GPUTextureUsage/RENDER_ATTACHMENT}} usage. However, the source/destination is restricted based on the format.
+All depth formats support {{GPUTextureUsage/COPY_SRC}}, {{GPUTextureUsage/COPY_DST}}, {{GPUTextureUsage/TEXTURE_BINDING}}, and {{GPUTextureUsage/RENDER_ATTACHMENT}} usage.
+However, the source/destination of copy operations is restricted based on the format.
 
 None of the depth formats can be filtered.
 
