1438068 - Scrolled area canvas blank repaint while scrolling

Status: RESOLVED DUPLICATE of bug 1437374

(Core :: Graphics, defect, P3)

Description

[Karl Dubost💡 :karlcow]

This is a spin off of https://webcompat.com/issues/15396


Seems like a recent regression: been using Nightly and Devdocs before and cannot recall such apparent 'tearing'.
Observed such blank scrolled layer 'flashes' on other sites as well, but with very varying reproducibility. Mostly just brief flash of blankness occurs during (manual) scroll, but here at devdocs I've observer "persistent blankness until scrollbar was dropped".

Nightly 60.0a1 build 20180211220056

Screengrab if attachment fails (yes, it fails):
https://i.imgur.com/giiiN3N.gif

gfx.webrender.all: false
gfx.webrender.blob-images: 1
gfx.webrender.enabled: false
image.mem.shared: 2

Comment 1

[Emilio Cobos Álvarez [:emilio]]

Sounds like graphics to me, off-hand :)

Comment 2

[Timothy Nikkel (:tnikkel)]

Since it only happens at the start I suspect that scrollframe didn't get a displayport until after it was scrolled.

Comment 3

[Michal Čaplygin [:myf]]

Attachment: about_support.json

Comment 4

[Michal Čaplygin [:myf]]

Attachment: nightly-2018-02-12-scroll-paint-blank-canvas.gif

Comment 5

[Michal Čaplygin [:myf]]

(In reply to Timothy Nikkel (:tnikkel) from comment #2)
> Since it only happens at the start (…)

Actually, it happens even when returning to once rendered area: see the gif, the the second scrolling up. It is the moment when actual paint occurs when the left mouse button holding scrollbar is released.

It happens quite randomly, sometimes I scroll page and get painted borders but not text. And very rarely I got partially blank page area (after scroll mostly) with content painted only after some interaction - sometimes only selecting part of the invisible text content makes whole layer appear. But it is really hard to reproduce. (My graphics otherwise works OK, drivers are actual, and as I mentioned, started observing this glitch just recently. Attached support json and actual screengrab gif for reference.)

Comment 6

[Michal Čaplygin [:myf]]

Attachment: Nightly_unpainted-text-layer-appears-after-selection-2018-02-15.gif

Got lucky and managed to capture the "invisible until selected" glitch described above; attaching the capture, page recorded is https://webcompat.com/issues/15396 .

Comment 7

[Timothy Nikkel (:tnikkel)]

Could be a dupe of bug 1437374.

Comment 8

[Michal Čaplygin [:myf]]

(In reply to Timothy Nikkel (:tnikkel) from comment #7)
> Could be a dupe of bug 1437374.

Yes, seems like; fix for it is shipped to Nightly and I can confirm I cannot reproduce both testcases from here. (Hooray!)