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[hal] allow for PreMultiplied alpha mode on the web #7993

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[hal] allow for PreMultiplied alpha mode on the web #7993

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5 changes: 4 additions & 1 deletion wgpu-hal/src/gles/adapter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1232,7 +1232,10 @@ impl crate::Adapter for super::Adapter {
} else {
vec![wgt::PresentMode::Fifo] //TODO
},
composite_alpha_modes: vec![wgt::CompositeAlphaMode::Opaque], //TODO
composite_alpha_modes: vec![
wgt::CompositeAlphaMode::Opaque,
wgt::CompositeAlphaMode::PreMultiplied,
], //TODO
Comment on lines +1235 to +1238
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I don't think this is right - without telling this to the runtime at all we can't know if these modes are actually supported. I'm not sure how this works with the various platforms, but I don't think we can just change it.

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It look like premultipliedAlpha is set to true by default https://registry.khronos.org/webgl/specs/latest/1.0/#5.2 and we do not seem to change it

maximum_frame_latency: 2..=2, //TODO, unused currently
current_extent: None,
usage: wgt::TextureUses::COLOR_TARGET,
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5 changes: 4 additions & 1 deletion wgpu/src/backend/webgpu.rs
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Expand Up @@ -3735,7 +3735,10 @@ impl dispatch::SurfaceInterface for WebSurface {
formats,
// Doesn't really have meaning on the web.
present_modes: vec![wgt::PresentMode::Fifo],
alpha_modes: vec![wgt::CompositeAlphaMode::Opaque],
alpha_modes: vec![
wgt::CompositeAlphaMode::Opaque,
wgt::CompositeAlphaMode::PreMultiplied,
],
// Statically set to RENDER_ATTACHMENT for now. See https://gpuweb.github.io/gpuweb/#dom-gpucanvasconfiguration-usage
usages: wgt::TextureUsages::RENDER_ATTACHMENT,
}
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