Add layer observer based on raw-window-metal

[madsmtm]

After #6107, resizing is still broken, and the right way to fix it is to create a sublayer that resizes itself based on the superlayer using key-value observing (see this for an introduction).

I have written a crate for this already, called raw-window-metal and filed #6210, but that crate depends on objc2, which is still under review by Firefox/Mozilla. So in the meantime, let's fix this directly in Wgpu.

Fixes #7011 and a few other issues, and should be fairly cleanly backport-able to v23 or v24 if desired.

I didn't write all that much documentation and safety comments here, and was kinda sloppy in some places, because the hope is that this fix will be temporary.

Testing
Tested by cherry-picking onto v23.1.0, and running Bevy's mobile example in the iOS simulator.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy.
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[teoxoy]

The changes look fine to me but it would be nice to get some confirmation from original reporters that this indeed fixes their issues.

cc @polina4096 & I will leave a comment in bevyengine/bevy#16604 as well.

[extrawurst]

I would love to test this but just a normal bevy example (sprite) now fails using that branch:

cargo r --example sprite

...

thread 'main' panicked at /Users/stephan/.cargo/git/checkouts/wgpu-be909407e42442b4/41b4b0f/wgpu/src/backend/wgpu_core.rs:1082:26:
wgpu error: Validation Error

Caused by:
  In Device::create_bind_group_layout, label = 'mesh_view_layout'
    Bind groups may not contain both a binding array and a dynamically offset buffer

just to make sure i have not missed a crate, these are the ones i patched:

[patch.crates-io]
wgpu = { git = "https://github.com/madsmtm/wgpu.git", branch = "metal-layer-observer" }
wgpu-types = { git = "https://github.com/madsmtm/wgpu.git", branch = "metal-layer-observer" }
naga = { git = "https://github.com/madsmtm/wgpu.git", branch = "metal-layer-observer" }

[teoxoy]

That is a new restriction for binding arrays added in #6811.

You could try an example that doesn't use binding arrays or find a way to turn off binding array usage.

@cwfitzgerald - I doubt the new restriction will be a blocker for bevy - but putting it on your radar just in case.

[cwfitzgerald]

Yeah I'll let them know about it

[cwfitzgerald]

If no one has tested this by next maintainers meeting, we'll merge it.

[HackerFoo]

I've tested that this PR works by cherry picking on top of wgpu-v24.0.1, and trying both my app on a device, and the Bevy example in the iOS simulator.

[cwfitzgerald]

Amazing! Thank you!