From 7e72f30179744ebb2b62603ee6a016d9bf22f1bc Mon Sep 17 00:00:00 2001
From: Teodor Tanasoaia <28601907+teoxoy@users.noreply.github.com>
Date: Fri, 3 Mar 2023 18:24:17 +0100
Subject: [PATCH] Allow copying of textures with copy-compatible formats
 (#3528)

Co-authored-by: Connor Fitzgerald <connorwadefitzgerald@gmail.com>
---
 CHANGELOG.md                      |  1 +
 wgpu-core/src/command/transfer.rs | 19 ++++++++++---------
 wgpu-hal/src/metal/command.rs     | 12 ++++++++++--
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6af899b529..d09a341267 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -94,6 +94,7 @@ By @teoxoy in [#3534](https://github.com/gfx-rs/wgpu/pull/3534)
 - Added `TextureFormatFeatureFlags::MULTISAMPLE_X16`. By @Dinnerbone in [#3454](https://github.com/gfx-rs/wgpu/pull/3454)
 - Support stencil-only views and copying to/from combined depth-stencil textures. By @teoxoy in [#3436](https://github.com/gfx-rs/wgpu/pull/3436)
 - Added `Features::SHADER_EARLY_DEPTH_TEST`. By @teoxoy in [#3494](https://github.com/gfx-rs/wgpu/pull/3494)
+- Allow copying of textures with copy-compatible formats. By @teoxoy in [#3528](https://github.com/gfx-rs/wgpu/pull/3528)
 - Improve attachment related errors. By @cwfitzgerald in [#3549](https://github.com/gfx-rs/wgpu/pull/3549)
 - Make error descriptions all upper case. By @cwfitzgerald in [#3549](https://github.com/gfx-rs/wgpu/pull/3549)
 
diff --git a/wgpu-core/src/command/transfer.rs b/wgpu-core/src/command/transfer.rs
index 5354485901..dee1ce35f6 100644
--- a/wgpu-core/src/command/transfer.rs
+++ b/wgpu-core/src/command/transfer.rs
@@ -120,9 +120,9 @@ pub enum TransferError {
     #[error("The entire texture must be copied when copying from depth texture")]
     InvalidDepthTextureExtent,
     #[error(
-        "Source format ({src_format:?}) and destination format ({dst_format:?}) are not copy-compatible"
+        "Source format ({src_format:?}) and destination format ({dst_format:?}) are not copy-compatible (they may only differ in srgb-ness)"
     )]
-    MismatchedTextureFormats {
+    TextureFormatsNotCopyCompatible {
         src_format: wgt::TextureFormat,
         dst_format: wgt::TextureFormat,
     },
@@ -1036,13 +1036,14 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
             .get(destination.texture)
             .map_err(|_| TransferError::InvalidTexture(source.texture))?;
 
-        // src and dst texture format must be the same.
-        let src_format = src_texture.desc.format;
-        let dst_format = dst_texture.desc.format;
-        if src_format != dst_format {
-            return Err(TransferError::MismatchedTextureFormats {
-                src_format,
-                dst_format,
+        // src and dst texture format must be copy-compatible
+        // https://gpuweb.github.io/gpuweb/#copy-compatible
+        if src_texture.desc.format.remove_srgb_suffix()
+            != dst_texture.desc.format.remove_srgb_suffix()
+        {
+            return Err(TransferError::TextureFormatsNotCopyCompatible {
+                src_format: src_texture.desc.format,
+                dst_format: dst_texture.desc.format,
             }
             .into());
         }
diff --git a/wgpu-hal/src/metal/command.rs b/wgpu-hal/src/metal/command.rs
index 25e355a32b..1b83f0f112 100644
--- a/wgpu-hal/src/metal/command.rs
+++ b/wgpu-hal/src/metal/command.rs
@@ -1,5 +1,5 @@
 use super::{conv, AsNative};
-use std::{mem, ops::Range};
+use std::{borrow::Cow, mem, ops::Range};
 
 // has to match `Temp::binding_sizes`
 const WORD_SIZE: usize = 4;
@@ -187,6 +187,14 @@ impl crate::CommandEncoder<super::Api> for super::CommandEncoder {
     ) where
         T: Iterator<Item = crate::TextureCopy>,
     {
+        let dst_texture = if src.format != dst.format {
+            let raw_format = self.shared.private_caps.map_format(src.format);
+            Cow::Owned(objc::rc::autoreleasepool(|| {
+                dst.raw.new_texture_view(raw_format)
+            }))
+        } else {
+            Cow::Borrowed(&dst.raw)
+        };
         let encoder = self.enter_blit();
         for copy in regions {
             let src_origin = conv::map_origin(&copy.src_base.origin);
@@ -199,7 +207,7 @@ impl crate::CommandEncoder<super::Api> for super::CommandEncoder {
                 copy.src_base.mip_level as u64,
                 src_origin,
                 extent,
-                &dst.raw,
+                &dst_texture,
                 copy.dst_base.array_layer as u64,
                 copy.dst_base.mip_level as u64,
                 dst_origin,