678134 - With GL layers on X11/NVIDIA, selecting text erases the text

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Benoit Jacob [:bjacob] (mostly away)]

STR:
1. enable GL layers, restart browser
2. Go to any web page that has text. I got this on bugzilla.mozilla.org main page, on about:memory, ...
3. play with selecting and deselecting text on that page. After a while (every roughly 5-10 tries) you can get into a situation where the text you had selected completely disappears when you deselect it.

Comment 1

[Benoit Jacob [:bjacob] (mostly away)]

Note: this is with NVIDIA 270.41.19 on a Quadro FX 880M

Comment 2

[Benoit Jacob [:bjacob] (mostly away)]

In MOZ_GL_DEBUG mode, it's almost impossible to reproduce the bug. Had to try for a couple minutes. This hints at a possible synchronization problem between GL and X, given that the main difference that MOZ_GL_DEBUG makes is that it calls glFinish after every GL function.

There always is a little bit of flicker when selecting text. The selected text disappears for a very short time before being repainted in the selection. In MOZ_GL_DEBUG that problem is more visible, but that could be just a consequence of MOZ_GL_DEBUG being slow.

There is no GL error at all.

Comment 3

[Benoit Jacob [:bjacob] (mostly away)]

The problem still occurs with NVIDIA 280.13.

In some cases I've had only a triangle of text rendered. My understanding is that we're rendering quads as 2 triangles and in this case only one of the two triangles had been painted by the time we did the compositing.

This hints strongly toward a syncing issue (see comment 2).

Comment 4

[Benoit Jacob [:bjacob] (mostly away)]

Attachment: screenshot for the "triangle effect" that I started seeing with NVIDIA 280.13

It's worth saying that I didn't really see the "triangle effect" before the NVIDIA 280.13 upgrade. Before that, only whole quads were missing.

Comment 5

[Matt Woodrow (:mattwoodrow)]

The only time we render triangles is when drawing textures onto our window. Swapping the buffers at the end of compositing should wait for all of these operations to finish.

That said, it's a pretty bizarre looking screenshot.

Comment 6

[Benoit Jacob [:bjacob] (mostly away)]

This is fixed by the patch v2 in bug 675474 !

Comment 7

[Benoit Jacob [:bjacob] (mostly away)]

Should be fixed by 675474, will verify in tomorrow's nightly.