1389492 - helper_key_scroll can intermittently time out

Status: RESOLVED FIXED

(Core :: Panning and Zooming, enhancement, P3)

Description

[Kartikaya Gupta (email:[e-mail])]

See Stone's investigation in bug 1351148 comment 156. What he found (which makes sense to me) is that since the VK_END scroll is running on the main thread, waiting for it to finish via waitForApzFlushedRepaints is incorrect. That function is intended to wait for APZ-side stuff to finish. In this case waitForApzFlushedRepaints might run the provided callback while the main-thread AsyncScroll thing is still going and triggering repaints.

I think if we take control of the refresh driver and tick it a few times that should be sufficient to let the AsyncScrollCallback calls finish up. I'm working on a patch to do this.

Comment 1

[Kartikaya Gupta (email:[e-mail])]

Attachment: Bug 1389492 - Ensure the helper_key_scroll waits for repaints from the main-thread scroll to finish before triggering the async scroll.

Review commit: https://reviewboard.mozilla.org/r/167570/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/167570/

Comment 2

[Kartikaya Gupta (email:[e-mail])]

Comment on attachment 8896297 [details]
Bug 1389492 - Ensure the helper_key_scroll waits for repaints from the main-thread scroll to finish before triggering the async scroll.

Stone, can you check if this fixes the problem for you?

Comment 3

[Ryan Hunt [:rhunt]]

Comment on attachment 8896297 [details]
Bug 1389492 - Ensure the helper_key_scroll waits for repaints from the main-thread scroll to finish before triggering the async scroll.

https://reviewboard.mozilla.org/r/167570/#review172808

This seems reasonable to me. Thanks for adding better logging info also.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/eeb77c809dc0
Ensure the helper_key_scroll waits for repaints from the main-thread scroll to finish before triggering the async scroll. r=rhunt

Comment 5

[Ming-Chou Shih [:stone]]

Comment on attachment 8896297 [details]
Bug 1389492 - Ensure the helper_key_scroll waits for repaints from the main-thread scroll to finish before triggering the async scroll.

It works for me. Can't reproduce it in local and on try server. Thanks.

Comment 6

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/eeb77c809dc0

Comment 7

[Gerry Chang [:gchang]]

Too late for 56. Mass won't fix for 56.