Pipelined Rendering: bevy does not request surface compatibility from wgpu

[branan]

Bevy version

pipelined-rendering HEAD

Operating system & version

Ubuntu 20.04

What you did

• Set prime to intel-only mode
• cargo run --example 3d_scene_pipelined

What you expected to happen

3d_scene_pipelined demo to be rendered on the Intel GPU

What actually happened

thread 'main' panicked at 'Error in Surface::configure: surface does not support the adapter's queue family', /home/branan/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.11.0/src/backend/direct.rs:204:9

Additional information

The reason that wgpu selects the intel GPU even though it cannot present to it is because Bevy does not request surface compatibility when initializing the wgpu adapter.

This happens in my case because wgpu is overly-aggressive in disabling presentation on Intel GPUs on systems with prime/optimus. However, I believe that this lack of an explicit compatibility check could potentially cause wgpu to select an incorrect Vulkan device in other situations where there are GPUs which cannot present.

[branan]

To be clear I believe there's both a wgpu bug and a bevy bug here:

• Bevy should explicitly request surface compatibility when initializing the renderer alongside winit. This isn't needed for headless rendering, obviously
• wgpu should be more targeted in its workaround for bad prime configurations

[branan]

Were I to attempt to fix this in Bevy myself, I think I'd:

• Reorder things so that the winit plugin is initialized before the renderer plugin
• Have the winit plugin do the primary window creation in its plugin setup, rather than waiting for the first run tick
• Have the renderer plugin query for windows in its own setup and use that to ask for compatibility from wgpu

This could still cause a non-compatible GPU to be selected when an initially-windowless app creates its first window later, but that's much more of an edge case.

This feels like a big refactor, though.

[bjorn3]

Since #3039 surface compatibility should be requested.

[superdump]

Does this work on current main?