1611060 - ScrollingEnd event not fired for scrollable areas other than the document itself

Status: RESOLVED FIXED

(Core :: Disability Access APIs, defect, P2)

Description

[James Teh [:Jamie]]

Reported to me by a ZoomText engineer.
When a document is scrolled in Firefox, we fire EVENT_SCROLLING_END. However, we don't fire any event when scrolling happens within a nested scrollable area.
Impact: This means that the ZoomText cursor enhancement stays in the wrong location when, for example, scrolling a message being composed in the Gmail message composer.

STR:

1. Open this test case:
   data:text/html,<div style="height: 500px; overflow: scroll;"><p>foo</p><hr style="height: 2000px;"><p>bar</p>
2. Monitor for EVENT_SCROLLING_END events.
3. Scroll down from foo.
   • Expected: EVENT_SCROLLING_END should be fired.
   • Actual: It isn't.

Currently, we add a scroll position listener for the document only:
https://searchfox.org/mozilla-central/rev/e878e5b81bb319c141900ce9cfcde732df5c8449/accessible/base/NotificationController.cpp#643
https://searchfox.org/mozilla-central/rev/e878e5b81bb319c141900ce9cfcde732df5c8449/accessible/generic/DocAccessible-inl.h#87
To fix this, we'd need to add a scroll position listener for any Accessible which has a scrollable frame.
Furthermore, document scrolling events are deferred using a timer to avoid flooding. I guess we'd need to do the same for any other scrollable frame.

Comment 1

[James Teh [:Jamie]]

Eitan, any thoughts here?

Comment 2

[Eitan Isaacson [:eeejay]]

Yeah. It seems like scroll events should not be exclusive to documents. I'll take this.

Comment 3

[Eitan Isaacson [:eeejay]]

Attachment: Bug 1611060 - Dispatch a11y scroll events for all DOM scrolls. r?Jamie!

Currently, only documents dispatch scroll events when in reality any
element can have scrollable overflows.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1e75ce1fef67
Dispatch a11y scroll events for all DOM scrolls. r=Jamie

Comment 5

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/1e75ce1fef67