1918138 - Ensure that shadows are correctly baked into VT snapshots

Status: RESOLVED FIXED

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

Description

[Nicolas Silva [:nical]]

Normally, if the stacking context has drop shadows we would render the stacking context into an off-screen surface and render the blur under it in the parent picture.

To do this properly with view-transitions we need to either

• bake the shadows into the snapshot.
• add some info about effects such as shadows to the snapshot and draw the shadows whenever the snapshot's image is drawn.

I suspect that the former would be simpler.

Comment 1

[Nicolas Silva [:nical]]

I am concerned that getting this right will require the content side to be able to know the exact inflated bounds of the stacking context to account for the shadow and correctly position and size the image display item of the snapshot.

It may be simpler to implement on the display-list building side instead of WebRender, by snapshotting without the shadows and wrapping the snapshotted images with the shadows.

Comment 2

[Nicolas Silva [:nical]]

Attachment: Bug 1918138 - Add a wrench test for snapshots with shadows. r=#gfx-reviewers

Depends on D231939

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5a7a8a6c90aa
Add a wrench test for snapshots with shadows. r=jnicol

Comment 4

[Atila Butkovits]

Backed out for causing WR bustages.

Backout link: https://hg.mozilla.org/integration/autoland/rev/89c1825a29bcfe5157d543b6425849a8627a6873

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=03b773761f5d40ee501204a1d596c5dde90cb6f7

Failure log:
https://treeherder.mozilla.org/logviewer?job_id=490199534&repo=autoland&lineNumber=48237

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/57020ef53c55
Add a wrench test for snapshots with shadows. r=jnicol

Comment 6

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/57020ef53c55