Allow copying from depth textures (#901)

* Allow copying from depth textures

* Rename TextureFormat::is_depth_format to just is_depth

* Only allow Depth32Float format for copying, and only as source

wgpu-core/src/command/transfer.rs

@@ -84,6 +84,10 @@ pub enum TransferError {
     InvalidRowsPerImage,
     #[error("source and destination layers have different aspects")]
     MismatchedAspects,
+    #[error("copying from textures with format {0:?} is forbidden")]
+    CopyFromForbiddenTextureFormat(wgt::TextureFormat),
+    #[error("copying to textures with format {0:?} is forbidden")]
+    CopyToForbiddenTextureFormat(wgt::TextureFormat),
 }
 
 /// Error encountered while attempting to do a copy on a command encoder.
@@ -480,6 +484,11 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         )?;
 
         let (block_width, _) = conv::texture_block_size(dst_texture.format);
+        if !conv::is_valid_copy_dst_texture_format(dst_texture.format) {
+            Err(TransferError::CopyToForbiddenTextureFormat(
+                dst_texture.format,
+            ))?
+        }
 
         let buffer_width = (source.layout.bytes_per_row / bytes_per_block) * block_width;
         let region = hal::command::BufferImageCopy {
@@ -594,6 +603,11 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         )?;
 
         let (block_width, _) = conv::texture_block_size(src_texture.format);
+        if !conv::is_valid_copy_src_texture_format(src_texture.format) {
+            Err(TransferError::CopyFromForbiddenTextureFormat(
+                src_texture.format,
+            ))?
+        }
 
         let buffer_width = (destination.layout.bytes_per_row / bytes_per_block) * block_width;
         let region = hal::command::BufferImageCopy {

wgpu-core/src/conv.rs

@@ -439,11 +439,10 @@ pub fn texture_block_size(format: wgt::TextureFormat) -> (u32, u32) {
         | Tf::Rgba16Float
         | Tf::Rgba32Uint
         | Tf::Rgba32Sint
-        | Tf::Rgba32Float => (1, 1),
-
-        Tf::Depth32Float | Tf::Depth24Plus | Tf::Depth24PlusStencil8 => {
-            unreachable!("unexpected depth format")
-        }
+        | Tf::Rgba32Float
+        | Tf::Depth32Float
+        | Tf::Depth24Plus
+        | Tf::Depth24PlusStencil8 => (1, 1),
 
         Tf::Bc1RgbaUnorm
         | Tf::Bc1RgbaUnormSrgb
@@ -562,6 +561,22 @@ pub fn is_power_of_two(val: u32) -> bool {
     val != 0 && (val & (val - 1)) == 0
 }
 
+pub fn is_valid_copy_src_texture_format(format: wgt::TextureFormat) -> bool {
+    use wgt::TextureFormat as Tf;
+    match format {
+        Tf::Depth24Plus | Tf::Depth24PlusStencil8 => false,
+        _ => true,
+    }
+}
+
+pub fn is_valid_copy_dst_texture_format(format: wgt::TextureFormat) -> bool {
+    use wgt::TextureFormat as Tf;
+    match format {
+        Tf::Depth32Float | Tf::Depth24Plus | Tf::Depth24PlusStencil8 => false,
+        _ => true,
+    }
+}
+
 pub fn map_texture_dimension_size(
     dimension: wgt::TextureDimension,
     wgt::Extent3d {

wgpu-core/src/device/queue.rs

@@ -313,6 +313,9 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
             size,
         )?;
         let (block_width, block_height) = conv::texture_block_size(texture_format);
+        if !conv::is_valid_copy_dst_texture_format(texture_format) {
+            Err(TransferError::CopyToForbiddenTextureFormat(texture_format))?
+        }
         let width_blocks = size.width / block_width;
         let height_blocks = size.height / block_width;