Mozilla/5.0 (X11; Linux i686; en-US; rv:2.0b2pre) Gecko/20100718 Minefield/4.0b2pre STEPS TO REPRODUCE: 1. Load http://tests.themasta.com/tinderboxpushlog/ 2. Scroll up and down, keeping a close eye on the colorful letters. ACTUAL RESULTS: During scrolling, some of the letters repaint with a darker 1px-wide stripe on their left edge. Once the scroll completes, the letters seem to "settle" in to their final no-stripe rendering. See upcoming screenshots. I first noticed this right around when retained layers landed -- given that this is a scrolling-dependent repaint bug, I think this is likely to be a regression from that. Marking as blocking that bug.

Here's a screenshot taken after the scroll completed, to demonstrate what tbpl normally looks like, for comparison vs. the buggy screenshot. (I took this screenshot a few minutes after the last one, actually, so the content changed slightly, but not very much.)

Probably just no-AA rendering. Do you get the same results with rendering text into an opacity:0.99 surface?

Ah! Yes, I do.

Here's the screenshot of what I see in the attached testcase, in case it looks different on other platforms. Note the stripe along the left edge of the "B" characters on the first line.

Note: I get the same results on the attached testcase in a 1.9.2 build... Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.7pre) Gecko/20100630 Namoroka/3.6.7pre ...but I haven't been able to reproduce the tbpl issue in 1.9.2. (though tbpl scrolls faster in 1.9.2, so maybe it's just less noticeable there)

Retained layers made the non-AA rendering kick in while scrolling. I can fix that for tbpl, but not everywhere. Should probably morph this into a bug on better text rendering in translucent X surfaces.

This works for me on Ubuntu 10.04; does it depend on X drivers?

Broken for me on both nvidia & ATI drivers. dbaron just thought to check font-settings too, and it turns out that's the difference that kept him from seeing the bug in comment 9. I have Subpixel Smoothing enabled (the default), whereas he had "Best Shapes". When dbaron turns on Subpixel Smoothing, then he sees this bug.

Also, for anyone else testing this: after changing font settings in gnome-appearance-properties, you only need to refresh the testcase to get an updated (working or broken) rendering. (No need to restart Firefox.)

Is this still broken? We fixed some things related to this.

No, no broken anymore - hooray! Testcase is WORKSFORME (no dark bars) in today's nightly: Mozilla/5.0 (X11; Linux x86_64; rv:2.0b12pre) Gecko/20110209 Firefox/4.0b12pre (I also verified that it's still broken in an older nightly (20101224) on this machine, to make sure that I'm not just inadvertently working around it somehow.) Resolving WORKSFORME (but feel free to change to FIXED if you know what fixed it).