1421472 - Flickering text rendering in text area

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[(not currently active) Ted Mielczarek]

Attachment: flickering

I pasted some text into a Bugzilla attachment textarea on another bug, and I noticed that when I scrolled to the top there was part of a line of text visible at the bottom and it was flickering. Attached is a short screen capture of the flickering.

STR:
- Paste some text into the text area on the Bugzilla attachment screen such that a partial line of text is visible when scrolled to the top.
- Scroll down then back up

Comment 1

[(not currently active) Ted Mielczarek]

Attachment: contents of about:support

I forgot to mention, this is on today's nightly on Windows 10.

Comment 2

[Darkspirit]

> NVIDIA Quadro M2000

Comment 3

[Darkspirit]

Attachment: 2017-11-29_01-27-41.mp4

Confirmed in
Nightly 59 x64 20171128100440 de_DE 5b33b070378ae0806bed0b5e5e34de429a29e7db @ Debian Testing (KDE, Radeon RX480).
fresh profile: layers.acceleration.force-enabled, gfx.webrender.enabled, gfx.webrender.blob-images, image.mem.shared, gfx.webrender.debug.alpha-primitives, gfx.webrender.highlight-painted-layers

https://bugzilla.mozilla.org/enter_bug.cgi?product=Core

See attached video.

Fixed by disabling WebRender.

Comment 4

[Darkspirit]

Attachment: 2017-11-29_01-31-17.mp4

(Wanted to test layout.display-list.retain;false here.)

This is a wonderful example where the blinking cursor (above "STR:" at the bottom) is the cause.

Comment 5

[Markus Stange [:mstange]]

This is caused by a limitation in WebRender's API which is tracked by bug 1409442. Setting dependency.

(The caret and the text should be clipped by two different clips but scrolled by the same scroll frame. Due to the limitation, whenever the caret is visible, the text is clipped to the same clip as the caret (instead of something smaller) and is drawn outside of where it should be.)

Comment 8

[Jeff Muizelaar [:jrmuizel]]

This, as expected, appears to be fixed by bug 1409442.