1524117 - Skip mix-blend modes when we're blending on top of transparency

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement)

Description

[Matt Woodrow (:mattwoodrow)]

From the formula at https://drafts.fxtf.org/compositing-1/#generalformula

If the backdrop alpha is 0 (as it will be if the mix-blend mode container is the first primitive in a stacking context), then the blend mode parameter gets multiplied by 0, and no longer matters.

We can do less work in some cases because of this.

Hoving over client logos on singlesprout.com GPU time goes from 2ms -> 1.4ms on my machine with this.

Comment 1

[Matt Woodrow (:mattwoodrow)]

Attachment: Bug 1524117 - Skip mix-blend mode operators in WebRender if we're sure they won't have any effect. r?gw

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/869fbaef1042
Skip mix-blend mode operators in WebRender if we're sure they won't have any effect. r=gw

Comment 3

[Narcis Beleuzu [:NarcisB]]

Backed out for wrench bustages on canvas.yaml.

Backout link: https://hg.mozilla.org/integration/autoland/rev/fa658b3963898dd0c8122092174a7266ca19027b
Push link: https://hg.mozilla.org/integration/autoland/rev/869fbaef1042f1872c6b8245c0edf10ad57a97c2
Log link: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=225163555&repo=autoland&lineNumber=2603

Comment 4

[Matt Woodrow (:mattwoodrow)]

Attachment: Bug 1524117 - Remove special handling for mix-blend modes on the root WebRender stacking context, since Gecko handles this already. r?gw

Depends on D18157

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1f1e882ed243
Skip mix-blend mode operators in WebRender if we're sure they won't have any effect. r=gw
https://hg.mozilla.org/integration/autoland/rev/4224ec9c27d3
Remove special handling for mix-blend modes on the root WebRender stacking context, since Gecko handles this already. r=gw

Comment 6

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/1f1e882ed243
https://hg.mozilla.org/mozilla-central/rev/4224ec9c27d3

Comment 7

[Paul Rouget [:paul]]

This broke some Servo tests: https://github.com/servo/webrender/issues/3594