1717297 - Make WebGL canvas opaque when possible

Status: RESOLVED INVALID

(Core :: Graphics: WebRender, enhancement)

Description

[Robert Mader [:rmader]]

Attachment: webgl demo with the Gnome opaque region overlay - green for opaque, purple for transparent

Testing different WebGL demos on https://webglsamples.org/ on Wayland with compositor integration reveals that we currently almost never make WebGL canvases opaque, effectively doubling the blitting bandwidth required in a (system) compositor.

This may be a bug in the sites code, however almost every WebGL canvas I encounter gets composited as not-opaque. It would be great if we could somehow detect cases where we can make the canvas opaque. This should improve performance on all internal or external compositors.

P.S.: to test this on Linux bug 1716044 is required

Comment 1

[Robert Mader [:rmader]]

Attachment: fullscreen webgl doom clone, with purple overlay for non-opaque

Comment 2

[Jeff Muizelaar [:jrmuizel]]

I'm not sure how we'd practically detect opaqueness if the canvas is isn't using the alpha: false context attribute. Do you have anything in mind for how to detect that?

Comment 3

[Robert Mader [:rmader]]

From all I can see it's too late for WebGL :(

I now opened https://github.com/gpuweb/gpuweb/issues/1871 for WebGPU, asking for a MacOS/Wayland/X11/Android style "please composite this assuming the alpha channel is actually all 1, with undefined results if it's not." hint.

Comment 4

[Robert Mader [:rmader]]

Closing this, as there's nothing actionable atm.