1229039 - Scrolling contacts sidebar in gmail doesn't work properly with APZ

Status: RESOLVED FIXED

(Core :: Panning and Zooming, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

It seems like it can get stuck at the top or bottom after scrolling through it the first time.

Comment 1

[Markus Stange [:mstange]]

This might be caused by the new preventDefault behavior that bug 1193062 introduced - calling preventDefault on a single scroll event will now cancel the whole scroll gesture. It's not clear whether that was a good idea.

Comment 2

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

I was able to repro this. It has to be repro'd in the hangouts contacts pane, which requires (AFAICT) a non-enterprise gmail account. From the log it doesn't look like it's a preventDefault that's causing it, more like the pan gesture block is getting prematurely discarded. I'll investigate.

Comment 3

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

I was wrong, it is a preventDefault that's causing it. The pan gesture block gets interrupted and so subsequent events are not processed in APZ until a new pan gesture block starts.

Comment 4

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

I discussed this with Markus and Botond and I think the way forward here is to treat pan inputs much like we do wheel inputs in the APZ. That is, a preventDefault for a pan input should just cause us to start new pan input block rather than dumping the rest of the inputs in that block. Right now once a pan input block is "interrupted" it basically goes away and the rest of the inputs go into the APZ black hole at [1] - they still get sent to content but with a 0 input block id which is not good, and they are ignored in the APZ code. I wrote patches to just create a new pan input block and it fixes the problem. Try push at [2].

[1] https://dxr.mozilla.org/mozilla-central/rev/0babaa3edcf908c393b68a3dc2d1c2a2450c31ed/gfx/layers/apz/src/InputQueue.cpp#329
[2] https://treeherder.mozilla.org/#/jobs?repo=try&revision=e96fb5c416b1

Comment 5

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

Attachment: Part 1 - Misc logging stuff

Comment 6

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

Attachment: Part 2 - Start a new pan gesture block if the old one was interrupted

Comment 7

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/6847b131a14b
https://hg.mozilla.org/integration/mozilla-inbound/rev/3e5a07114c82

Comment 8

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/6847b131a14b
https://hg.mozilla.org/mozilla-central/rev/3e5a07114c82