1595965 - White square at bottom right in about:support when os compositor was enabled on Windows.

Status: RESOLVED FIXED

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

Description

[Sotaro Ikeda [:sotaro]]

I saw it with latest nightly.

STR

• [1] Start Firefox with os compositor enabled on Windows.
  • gfx.webrender.compositor: true
• [2] Move to about:support

Actual result

• White square at bottom right in about:support.
• It seemed to happen when Firefox window was a certain size. Then if the problem does not happen, we could try resizing window horizontally.

Expected result

• No white square at bottom right

Comment 1

[Sotaro Ikeda [:sotaro]]

Attachment: screenshot

Screenshot when the white square appeared.

Comment 2

[Sotaro Ikeda [:sotaro]]

I tried mozregression, but I am not sure which change caused the problem.

./mach mozregression --good 2019-10-20 --pref gfx.webrender.all:true gfx.webrender.compositor:true -a about:support

https://hg.mozilla.org/mozilla-central/pushloghtml?changeset=caf55914ccddba34d462a1206530d7868b6c4992

Comment 3

[Sotaro Ikeda [:sotaro]]

There was another STR to cause white square.

STR

• [1] Start Firefox with os compositor enabled on Windows. But window is not maximized.
  • gfx.webrender.compositor: true
• [2] Move to a page like about: support
• [3] Enable menu bar
• [4] Select "Find in This Page" in Edit menu.

Actual result

• White square at bottom in about:support. When window was not maximized, the issue did not happen.
• It seemed to happen when Firefox window was a certain size. Then if the problem does not happen, we could try resizing window horizontally or vertically.

Expected result

• No white square at bottom

Comment 4

[Sotaro Ikeda [:sotaro]]

From the symptom, it seemed that some tiles of content were not rendered.

Comment 5

[Sotaro Ikeda [:sotaro]]

Attachment: screenshot of comment 3

Comment 6

[Sotaro Ikeda [:sotaro]]

:gw, can you reproduce the problem? Comment 3 was easy to reproduce. I could reproduce the issue on my all Win10 PCs.

Comment 7

[Sotaro Ikeda [:sotaro]]

Attachment: temporal patch - Add log

Comment 8

[Glenn Watson [:gw]]

Yes, I can reproduce this. I'll investigate today, thanks for the STR!

Comment 9

[Glenn Watson [:gw]]

Attachment: Bug 1595965 - Fix tile draw order with native compositor mode.

In Draw compositor mode, tiles are placed into a bucket based on
the tile kind and/or opacity. This simplifies the renderer code
for this mode, which uses the z-buffer to reject opaque tiles.

In native compositor mode, the tiles need to be submitted in the
correct draw order. Opacity is a property of the native surface,
and should not affect the order the tiles are added to the visual
tree of the native compositor.

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e7837d7a78c6
Fix tile draw order with native compositor mode. r=sotaro

Comment 11

[Daniel Varga [:dvarga]]

https://hg.mozilla.org/mozilla-central/rev/e7837d7a78c6

Comment 12

[ithompson4]

Fix Verified [testday-20191220]