1202714 - [OMTC] Firefox doesn't repaint hg.mozilla.org when I autoscroll it slowly

Status: RESOLVED DUPLICATE of bug 1209100

(Core :: Graphics, defect)

Description

[arni2033]

Attachment: video - [OMTC] Firefox doesn't repaint hg.mozilla.org when I autoscroll it slowly.webm

STR:   (Win7_64, Nightly 43, 32bit, ID 20150907030206, new profile, safe mode)
1. Open URL
2. Place mouse in the center of content area
3. Click middle mouse button
4. Move mouse 1-5px below the autoscroll circle

Result:       Page is being scrolled, but elements repaint only when I move mouse over them
Expectations: Page should repaint normally

Workaround:   1) html5.offmainthread -> false
              2) layers.offmainthreadcomposition.async-animations -> false
              3) layers.offmainthreadcomposition.enabled -> false
              4) Restart browser

Comment 1

[Markus Stange [:mstange]]

Does turning off e10s or APZ (layers.async-pan-zoom.enabled) also stop this from happening?

Comment 2

[arni2033]

As you can see on the video, e10s is not enabled. APZ doesn't stop this.
// You asked _me_ because you failed to reproduce this yourself, right?

Comment 3

[Markus Stange [:mstange]]

Correct.

Comment 4

[arni2033]

(In reply to Markus Stange [:mstange] from comment #3)
I saw you're using Mac OS. That's important information and should've been mentioned.

Comment 5

[arni2033]

I figured out that "layers.offmainthreadcomposition.enabled"->false is enough to cure it.

Markus, we have a theory that VM blocks/doesn't allow OMTC. (See bug 1189438 comment 13)

Comment 6

[arni2033]

I created user.js in my profile where I enabled OMTC (just in case) and bisected using that profile.
This was caused by bug 1165185. Regression range:
> https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=cd741d3ae78a7ef127b6baf7c4efc0fff0472267&tochange=f7fca0232ffc4ec5855557cfb7a6d039b28488e4

Comment 7

[arni2033]

Any success reproducing this bug on Windows?

Comment 8

[Markus Stange [:mstange]]

This is the same underlying bug as bug 1209100 - we're failing to recomposite at the bottom end of very large pages.