1946361 - Render missing stacking context snapshots as a transparent image

Status: RESOLVED FIXED

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

Description

[Nicolas Silva [:nical]]

There is a long tail of tricky cases where webrender fails to produce a stacking context snapshot. All of the known cases involve WebRender culling the snapshot more aggressively than it should. Typically it involves cases where the sacking context cannot be projected to the screen at the time of snapshotting (but ideally a snapshot should be produced in case the transition changes the transform in a way that makes the snapshot visible and renderable), or simply an empty stacking context (in which case producing a transparent image is the correct thing to do).

It would be best to handle each case specifically, but as we discover and go through new ones, the most graceful way to handle running into these cases is to fall back to rendering a transparent image. This may add transparency fade-in or fade-out transition to the animation that was not intended by the author in some cases, but it is better than crashing or canceling the transition.

Comment 1

[Nicolas Silva [:nical]]

Attachment: Bug 1946361 - Fallback to a transparent image for missing snapshots. r=gw

A followup patch will add debug prefs to panic or use pink instead of transparent
for the fallback image.

Comment 2

[Nicolas Silva [:nical]]

Attachment: Bug 1946361 - Add debug prefs for missing snapshots. r=gw

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7a4f645b7b18
Fallback to a transparent image for missing snapshots. r=gw
https://hg.mozilla.org/integration/autoland/rev/2170cebcbf0a
Add debug prefs for missing snapshots. r=gw

Comment 4

[pstanciu]

https://hg.mozilla.org/mozilla-central/rev/7a4f645b7b18
https://hg.mozilla.org/mozilla-central/rev/2170cebcbf0a