When viewing a large log file containing just text (here if that matters), occasionally a single line of text grows an extra line. It's at the bottom only and only at certain times. Looks like a rounding error, but I notice that it's always the same line that renders this way.

Using WebRender, Nvidia 1080 GPU. Happy to attach about:support if that helps.

I'd guess this is happening at "seams" between separately-painted tiles, or something like that. This isn't a Text problem, it would affect any content; it's just much easier to notice it when it runs through a line of text.

In the distant past we had problems that looked very similar whenever we did a scroll by some amount that wasn't exactly an integral number of display pixels -- this would result in moving part of what was displayed and then repainting the newly-visible area in a way that didn't perfectly line up. With today's architecture I could imagine something similar happening with tile boundaries rather painting rectangles that result from scrolling. Or it could be something entirely different...

That said, I've been seeing this as well... although now I'm forgetting which platform (Windows or Linux) I was seeing it on!

I'm curious what you mean by "at the bottom only" -- since that sounds like one of the old scrolling problems. If we decided to scroll to "exactly the bottom" of the page, rather than the bottom of the page rounded to an integer number of pixels -- that was once one of our major sources of non-integer scroll offsets.

Could be a dupe of: bug 1565473

(Martin Thomson [:mt:] from comment #0)

Using WebRender, Nvidia 1080 GPU.