Specified that XRWebGLLayer framebuffers always use premultiplied alpha #840
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Manishearth
reviewed
Sep 12, 2019
| @@ -1684,6 +1684,7 @@ An <dfn>opaque framebuffer</dfn> functions identically to a standard {{WebGLFram | |||
| - An [=opaque framebuffer=] initialized with {{XRWebGLLayerInit/depth}} <code>false</code> will not have an attached depth buffer. | |||
| - An [=opaque framebuffer=] initialized with {{XRWebGLLayerInit/stencil}} <code>false</code> will not have an attached stencil buffer. | |||
| - An [=opaque framebuffer=]'s color buffer will have an alpha channel if and only if {{XRWebGLLayerInit/alpha}} is <code>true</code>. | |||
| - The [=XR Compositor=] will assume the [=opaque framebuffer=] contains colors with premultiplied alpha. This is true regardless of the {{WebGLContextAttributes|premultipliedAlpha}} value set in the {{XRWebGLLayer/context}}'s [=actual context parameters=]. | |||
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If we do this we should probably also recommend a warning be displayed in this situation to properly fix #837
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I wondered about that, but it seems like recommending that the UA output a warning to the console falls outside of what specs typically dictate. At best we could put a non-normative note in that suggests it, but I'm not sure if the group feels like that's necessary?
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Yeah, a non normative note is what I meant. "UAs may want to show a warning to the console when a context created with premultipliedAlpha: false is passed to new XRWebGLLayer()"
We can also make it a hard error, but that might be too large a hammer.
thetuvix
approved these changes
Sep 16, 2019
NellWaliczek
approved these changes
Sep 19, 2019
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Not intended for merge until discussed at TPAC /facetoface
Would fix #837 and #838 if the working group's decision is that
XRWebGLLayers are always treated as using premultiplied alpha regardless of the source context's flags. Preparing this for easy approval should that be the case.