1713686 - Reduce forced redraws in SW-WR/RenderCompositorSWGL on Wayland

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement, P3)

Description

[Robert Mader [:rmader]]

IIUC similar to bug 1696101. Right now, at least on Linux, RenderCompositorOGLSWGL already reports significant less damage the system compositor compared to RenderCompositorSWGL. We should be able perform similarly.

Comment 1

[Robert Mader [:rmader]]

Attachment: Gnome damage overlay RenderCompositorSWGL

Comment 2

[Robert Mader [:rmader]]

Attachment: Gnome damage overlay RenderCompositorOGLSWGL

Comment 3

[Robert Mader [:rmader]]

So a bit of digging revealed that the culprit lies in this line: https://searchfox.org/mozilla-central/source/gfx/wr/webrender/src/render_backend.rs#1455-1458

should_redraw_on_invalidation is true for RenderCompositorSWGL but not for RenderCompositorOGLSWGL. Now I'll need to find out:

• why should_redraw_on_invalidation is different
• why invalidate_rendered_frame()[1] gets called in the first place (on both backends) and if that's a bug

1: https://searchfox.org/mozilla-central/source/gfx/wr/webrender/src/render_api.rs#376-378

Comment 4

[Robert Mader [:rmader]]

Turns out this a "regression" from bug 1690216 / https://phabricator.services.mozilla.com/D106246 - apparently the should_redraw_on_invalidation is necessary in some situations when the whole window gets unmapped on X11.

Unfortunately on sites like testufo.com we get a lot of invalidations from https://searchfox.org/mozilla-central/source/gfx/layers/wr/WebRenderBridgeParent.cpp#1469-1476.

Now I wonder if we should try to reduce the invalidations or rather limit should_redraw_on_invalidation to platforms that really need it (IIUC Wayland should not, while X11 might do).

Lee, as you wrote that patch, do you have any idea here?

Comment 5

[Robert Mader [:rmader]]

Attachment: Bug 1713686 - Disbale redraw_on_invalidation in RenderCompositorSWGL on Wayland, r=lsalzman,#gfx-reviewers

This was introduced in D106246, but it is not obvious that any
backend but X11 actually needs it. Notably the Wayland backend
most likely does not.

Removing it makes RenderCompositorSWGL behave (more) equally to
RenderCompositorOGLSWGL, massively reducing overpaint on certain
websites like testufo.com.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d39eb2d0e9d8
Disbale redraw_on_invalidation in RenderCompositorSWGL on Wayland, r=lsalzman,gfx-reviewers

Comment 7

[Marian-Vasile Laza]

https://hg.mozilla.org/mozilla-central/rev/d39eb2d0e9d8

Comment 8

[Robert Mader [:rmader]]

Dear sheriffs, please back out this patch from beta (91). For nightly/92 we have a fix, but it will need testing.

Comment 9

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Julien, Pascal, can you take the backout request for beta with the next batch of uplifts, please?

Comment 10

[Pascal Chevrel:pascalc]

Backed out changeset d39eb2d0e9d8 (bug 1713686) on beta for causing a regression (bug 1717351) a=backout
https://hg.mozilla.org/releases/mozilla-beta/rev/881ec252e382