arni2033 Reporter
	Description • 8 years ago

>>>   My Info:   Win7_64, Nightly 49, 32bit, ID 20160526082509
STR_1:
1. Extract attached "testcase 1" in a folder with short full name
2. Open .htm file


STR_2:  (origin of STR_1)
1. Open any imgur image, e.g. http://imgur.com/0Cw7aKJ or http://imgur.com/a/fTif0
2. Hover mouse over section with "Most viral images"
3. Rotate mouse wheel down once
4. Hover mouse over a not selected item in section (which isn't placed directly below mouse pointer)
5. Repeat steps 3-5


AR:  Fake scrollbar briefly (~0.5s) compresses/twitches by 1px to left and right
ER:  Fake scrollbar should not move horizontally. Shouldn't twitch/compress.

This is regression. Firefox 28 is unaffected, Nightly 49 is affected.

	Ciprian Muresan [:cmuresan], Ecosystem QA
	Comment 2 • 8 years ago

Narrowed nightly regression window from [2014-07-23, 2014-07-25] (2 days) to [2014-07-23, 2014-07-24] (1 days) (~0 steps left)
Got as far as we can go bisecting nightlies...
Last good revision: 82df3654cd80 (2014-07-23)
First bad revision: a91ec42d6a9c (2014-07-24)
Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=82df3654cd80&tochange=a91ec42d6a9c

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 3 • 8 years ago

I don't see any compression/twitching of the scrollbar, however I see that the rounded corners on the scrollbar seem to get pixellated when I scroll. It's barely visible, but the rounding is slightly less-than-perfect, and if I move the mouse to hover over a different item the scrollbar (presumably) gets repainted and goes back to looking perfect. Assuming that the bug I'm seeing has the same root cause, and based on the regression range in comment 2 I suspect this might be an invalidation/repainting bug.