931504 - Fire touchcancel for everytouch point the apz consumes

Status: RESOLVED FIXED

(Core Graveyard :: Widget: WinRT, defect)

Description

[Jim Mathies [:jimm]]

This fixes a bug where occasionally touch will stop working for content. In the current code, we fire off touchcancels if the apz starts consuming event using the touch list in mTouches. But since this is generated in the async callback touch points might have been removed from mTouches before the touchcancel touch list is generated.

The side effect of this bug is that sometimes the touchcancel event didn't have any touch points in it's array, and this threw off the code in presshell that tracks touch points. Which in turn borked touch for the rest of the browser session since touch points were left in gCaptureTouchList across touch blocks.

These changes make sure that every touch point sent to presshell and subsequently consumed by the apz receives a corresponding touch cancel.

Comment 1

[Jim Mathies [:jimm]]

Attachment: fix v.1

Comment 2

[Jim Mathies [:jimm]]

Attachment: fix v.1

- fix a comment typo.

Comment 3

[Tim Abraldes [:TimAbraldes] [:tabraldes]]

Comment on attachment 822940 [details] [diff] [review]
fix v.1

Review of attachment 822940 [details] [diff] [review]:
-----------------------------------------------------------------

::: widget/windows/winrt/MetroInput.cpp
@@ +1282,5 @@
> +    }
> +    mCanceledIds.AppendElement(id);
> +    if (!touchEvent) {
> +      touchEvent = new WidgetTouchEvent(true, NS_TOUCH_CANCEL, mWidget.Get());
> +    }

nit: This would look prettier to me if we set touchEvent before the loop, then only dispatched it if its 'touches' member was non-zero length.

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/c64f67f306ef