1946487 - "Layer Compositor" makes transparent windows have a black backdrop

Status: VERIFIED FIXED

(Core :: Widget: Win32, defect)

Description

[Mayank Bansal]

enable mica
Set gfx.webrender.layer-compositor = TRUE (this is off for now, but will become true in 1-2 days). Bug 1945683.

AR: The tab bars are black
ER: Not so.

Comment 1

[Mayank Bansal]

Attachment: Screenshot 2025-02-06 213920.png

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Glenn is it expected that the layer compositor doesn't support transparency?

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Mayank do you know if non-native alerts (alerts.useSystemBackend = true) show the same issue? (No shadow, black backdrop?)

Comment 4

[Mayank Bansal]

(In reply to Emilio Cobos Álvarez (:emilio) from comment #3)

Mayank do you know if non-native alerts (alerts.useSystemBackend = true) show the same issue? (No shadow, black backdrop?)

This preference is already true for me. I dont know how to test it though. Are these web notifications ?
I tried with https://cleverpush.com/en/test-notifications/, and the notifications look fine.

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Sorry I should've written alerts.useSystemBackend = false, ugh. https://www.bennish.net/web-notifications.html is my go-to page to test notifications. They should show an alert window drawn by Firefox rather than the windows notifications.

Comment 6

[Mayank Bansal]

Attachment: Screenshot 2025-02-06 220048.png

this is what i
They also stack on top of each other.
While disappearing, they sort of shimmer, turn black and then disappear.

Comment 7

[Emilio Cobos Álvarez (:emilio)]

Yeah, so not mica specific. There should be shadows rather than black borders.

Comment 8

[Glenn Watson [:gw]]

(In reply to Mayank Bansal from comment #6)

Created attachment 9464423 [details]
Screenshot 2025-02-06 220048.png

this is what i
They also stack on top of each other.
While disappearing, they sort of shimmer, turn black and then disappear.

I can't reproduce this locally with layer compositor enabled on current nightly, which is interesting. Does it still occur for you, and are there any other repro steps you can think of that may be relevant?

Comment 9

[Glenn Watson [:gw]]

Oh, never mind - I had incorrectly set the alerts backend pref, I can reproduce now, thanks.

Comment 10

[Glenn Watson [:gw]]

Attachment: Bug 1946487 - Fix transparent top level windows with layer compositor

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4a1a53ae485e
Fix transparent top level windows with layer compositor r=gfx-reviewers,lsalzman

Comment 12

[Mayank Bansal]

The autoland build also seems to fix all of the other regressio bugs i filed! I will wait for this patch to hit Nightly before duping them over.

Comment 13

[amarc]

https://hg.mozilla.org/mozilla-central/rev/4a1a53ae485e

Comment 14

[Mayank Bansal]

This is fixed on the latest Nightly.