1136734 - Bypass compositor for WebGL canvas elements in fullscreen mode.

Status: NEW

(Core :: Graphics: CanvasWebGL, defect, P3)

Description

[Mike de Boer [:mikedeboer]]

See URL for the relevant thread on the WebGL mailing list.

Quote from the first message in that tread:
"One of the issues with WebGL in particular on mobile is because WebGL has to be composited it loses a lot of performance. What I mean is WebGL renders to a texture. That texture is then drawn into the backbuffer in the correct order with other HTML elements. This effectively means a fullscreen WebGL app is drawing an entire extra screen worth of pixels vs a native app."

So once a canvas element goes fullscreen, it is expected that we can get quite the performance boost and framerate improvement if we can bypass the Gecko layout pipeline - the compositor - and write to the (GL) backbuffer directly.

This was also discussed on the dev-platform mailing list, starting here: https://lists.mozilla.org/pipermail/dev-platform/2015-January/008277.html

Comment 1

[Thibaut Despoulain]

Thank you for bringing this discussion here too, we'll be following this one closely as well!
Again, if you ever need a real-life example of such usage or potentially a testbed game, feel free to send me a mail and we'll give you access to Project Atlas' closed alpha.

Comment 2

[Kelsey Gilbert [:jgilbert]]

Yep, this is the plan. It'll take a little work, but it'd be really nice for a number of reasons. Hopefully something for Q2.

Comment 3

[Josh Carpenter [:jcarpenter]]

I can also provide large numbers of WebVR test cases.

Comment 4

[:kip (Kearwood Gilbert)]

I am removing the [webvr] tag as a VR specific rendering path that bypasses the compositor has been implemented as part of the WebVR 1.0 support in Bug 1250244.

Perhaps the VR specific implementation may be a good reference for someone implementing the general purpose WebGL case.