701812 - Text sometimes unclear, but OK after window move

Status: RESOLVED INCOMPLETE

(Core :: Graphics, defect)

Description

[Ben Bucksch (:BenB)]

Sometimes, when I change the virtual screen back and look at Thunderbird, the chrome text in the folder pane and thread pane looks very ugly, "frayed".

However, as soon as I move the window, everything is OK and crisp again.

Regression:
This appeared when I upgraded from Thunderbird 7.0 to 8.0. I have never seen this bug before, it didn't exist in TB 7.0.

OS environment:
I'm on Linux, with nouveau driver, Ubuntu 10.04. I think there is no or minimal 3D acceleration in this driver.

Comment 1

[Ben Bucksch (:BenB)]

xref bug 677144, bug 675840

Comment 2

[Ben Bucksch (:BenB)]

Attachment: Screenshot of live window, the same window having good and bad text

I had it again, this time after other windows were covering TB. Now I have a window which is partially with bad text and partially OK, quite odd. Where is a screenshot. You can clearly see the difference, where the text is OK and normal, and where the bug appears. This screen is not doctored or combined in any way (apart from blacking out private information), this appeared as you see it.

Please note that although you would suspect an OS / window system bug, my system didn't change (I didn't even reboot), and the bug never appeared on TB 7.0, but did appear several times since I changed to TB 8.0 today.

Also, given that the text is partially OK and partially not, this is clearly not a bug in Thunderbird, but in the Gecko rendering engine.

Comment 3

[Ben Bucksch (:BenB)]

Hello? This is a major bug by any standard. It's very ugly and very visible. Could somebody please fix this? Who's responsible for this component?

Comment 4

[Jonathan Kew [:jfkthame]]

It looks like some of the text has been painted/composited onto its background multiple times in such a way that faint antialiasing pixels have become much darker/more opaque than they should be.

Something to do with the invalidation and refreshing of layers when a (partially-obscured?) window is repainted, maybe? Roc, maybe you'd know where to look, or who could investigate?

Ben, if it's possible to describe an explicit sequence of steps that will consistently reproduce the problem, that would be helpful.

Comment 5

[Ben Bucksch (:BenB)]

It's most often when I change virtual workspaces. I don't have a 100% reproduction, I don't know what *exactly* triggers it, sorry, but it happens very often, I see it many times per day.
I have sometimes also seen it just with overlapping windows (screenshot attached), but much less often so.

Comment 6

[Ben Bucksch (:BenB)]

Here's my setup, in case that clues anybody in: 
From comment 0:
> OS environment:
> I'm on Linux, with nouveau driver, Ubuntu 10.04. I think there is no or minimal 3D
> acceleration in this driver.

2 identical TFT monitors, 1920x1200, DVI, both on the same nvidia graphics card.
X.Org X Server 1.7.6, nouveau driver, xrandr.
6 workspaces, changing often between them.

---

Thunderbird is sometimes covered by other windows, sometimes entirely visible when I change to the workspace. It think something along those lines, but more complex, is what triggers the bug.

Comment 7

[Ben Bucksch (:BenB)]

Attachment: GNOME anti-aliasing font settings

> text has been painted/composited onto its background multiple times in such a > way that faint antialiasing pixels have become much darker/more opaque than
> they should be.

Good theory. Here are my AA settings in GNOME.

> Something to do with the invalidation and refreshing of layers when
> a (partially-obscured?) window is repainted, maybe?

Most definitely related to repaints.
As said, once I move another window over it, the effect is gone. In fact, even a mouse over fixed it, right now.

Oh, and I have Thunderbird windows on several workspaces, in case that matters.

Comment 8

[Ryan VanderMeulen [:RyanVM]]

Safe to say this went away on its own?

Comment 9

[Ryan VanderMeulen [:RyanVM]]

Closing this as incomplete due to inactivity and lack of response from the reporter. Feel free to reopen the bug if the issue still reproduces on a current build.