wgpu: Allow wgpu on web and various improvements

[Herschel]

This is working towards several wgpu changes:

• Bump to latest wgpu 0.11, using the new wgpu-hal.
• Replace the use of push constants with uniforms.
  • Push constants are not part of the current WebGPU spec, and are provided as an extension in wgpu that is unfortunately not supported on most backends.
  • We'll need to do this to support WebGPU in the browser.
• The OpenGL backend should now function on Linux.
• Support sRGB surface formats by allowing shaders to perform the sRGB->linear conversion.
  • OpenGL does not support the non-sRGB surface format.
• Add web support for the wgpu backend.
  • wgpu feature added to ruffle_web.
  • Web will try to create wgpu renderer, WebGL renderer, and canvas renderer, in that order.
  • WebGPU currently requires Chrome Canary/Firefox Nightly with the proper flags enabled.
• Rewrite all shaders in WGSL.

Let's hold off on merging this until either the DX11 backend is re-enabled, or the OpenGL backend works on Windows.

[torokati44]

About the surface format issue: My experience was that only sRGBA formats were supported on OpenGL.

[Herschel]

Bumped to wgpu 0.11.

[torokati44]

After the bump to 0.11, it still works fine for me on native Linux; on both Vulkan with HW acceleration, and on OpenGL - with or without HW acceleration.
Now I only get these warnings, but they don't seem to matter:

[2021-10-11T20:25:07Z WARN  ruffle_render_wgpu] Open GL graphics backend support may not be fully supported.
[2021-10-11T20:25:07Z WARN  wgpu_core::instance] Missing downlevel flags: READ_ONLY_DEPTH_STENCIL
    The underlying API or device in use does not support enough features to be a fully compliant implementation of WebGPU. A subset of the features can still be used. If you are running this program on native and not in a browser and wish to limit the features you use to the supported subset, call Adapter::downlevel_properties or Device::downlevel_properties to get a listing of the features the current platform supports.
[2021-10-11T20:25:07Z WARN  wgpu_core::validation] Unexpected varying type: Array { base: [1], size: Constant([5]), stride: 4 }
[2021-10-11T20:25:07Z WARN  wgpu_core::validation] Unexpected varying type: Array { base: [1], size: Constant([5]), stride: 4 }
[2021-10-11T20:25:07Z WARN  wgpu_core::validation] Unexpected varying type: Array { base: [1], size: Constant([7]), stride: 4 }
[2021-10-11T20:25:07Z WARN  wgpu_core::validation] Unexpected varying type: Array { base: [1], size: Constant([7]), stride: 4 }
[2021-10-11T20:25:07Z WARN  wgpu_core::device] Surface does not support present mode: Mailbox, falling back to FIFO
[2021-10-11T20:25:07Z WARN  wgpu_core::device] Surface does not support present mode: Mailbox, falling back to FIFO

[Herschel]

I've converted all of the shaders over to WSGL. I don't think it's worth waiting for DX11 support, so this is more or less ready to go; unfortunately I'm getting errors on DX12 at the moment that I need to investigate.

@torokati44 Could you give this another try on your machine with OpenGL?

[torokati44]

Still works fine for me on all four [OpenGL, Vulkan] x [HW, SW] combinations.

[torokati44]

BTW is running with DX11 any better than OpenGL on Windows?
I'm not sure raw performance is that important for most content, I'm asking more about compatibility.

[Herschel]

Unfortunately wgpu OpenGL backend doesn't function on Windows (it uses egl for the context management, it would need to use wgl on Windows). And I don't think it's really on their roadmap to support OpenGL on Windows.

I don't know what machines would support DX11 but not DX12; DX12 was back-ported to Windows 7, and I think even integrated GPUs would support both DX11 and 12. But not 100% sure.

[Herschel]

To answer my own question a little bit, Intel provides this page indicating which APIs their chips support:
https://www.intel.com/content/www/us/en/support/articles/000005524/graphics.html

You actually don't need to fully support DX12 feature set to use DirectX 12; the versions are more like feature levels nowadays, and ostensibly you can use the DirectX12 API with the DX11 feature set. wgpu itself only requests D3D_FEATURE_LEVEL_11_0 which should in theory go all the way back to HD Graphics 2500.

HD Graphics 2000 is the first to only support DX10, and that's dating to 2011, so I think that's far enough back to be okay ignoring it.

[Herschel]

My DX12 issue mentioned above was kindly fixed in gfx-rs/wgpu#2103.

Unfortunately as far as Win7 goes, looks like Microsoft's D3D12on7 wrapper is required to use DX12 API on older Windows -- I mistakenly thought MS had seamlessly backported it. So this would require these pre-Win10 users to have Vulkan. Consulting back to the Intel support page, the chipsets that supposedly support Vulkan date back to only ~2015.

[Herschel]

Let's go ahead and merge this, with pre-emptive apologies to any users on older Win 7 systems.