1887790 - [UIA] Expose live regions

Status: RESOLVED FIXED

(Core :: Disability Access APIs, task)

Description

[James Teh [:Jamie] (away returning 12 Jan)]

We need to expose live regions to UIA clients. This will involve the LiveSetting property and the LiveRegionChanged event. However, exactly how these should be used to expose all live region semantics is rather unclear, so some investigation will be needed.

Comment 1

[James Teh [:Jamie] (away returning 12 Jan)]

This isn't clearly documented, but as well as the LiveSetting property, we need to do (at least) the following to get live regions working in Narrator:

1. IsControlElement/IsContentElement must return true for live regions. Otherwise, Narrator will fail to find changes inside them.
2. AriaProperties must always expose the value of aria-atomic; e.g. atomic=false. Otherwise, Narrator will assume the region is atomic and read the entire thing, rather than just updates.

StructureChanged events don't seem to make a difference. There might be more to learn as I do more complex testing.

Comment 2

[James Teh [:Jamie] (away returning 12 Jan)]

Attachment: Bug 1887790 part 1: Remove nsAccUtils::IsARIALive.

This isn't used any more and only works for LocalAccessible.

Comment 3

[James Teh [:Jamie] (away returning 12 Jan)]

Attachment: Bug 1887790 part 2: Implement the UIA LiveSetting property.

Comment 4

[James Teh [:Jamie] (away returning 12 Jan)]

Attachment: Bug 1887790 part 3: Expose aria-atomic via the UIA AriaProperties property.

UIA doesn't have a native property to expose aria-atomic, so we need to expose this via AriaProperties.
If it's not exposed, Narrator will assume true, so we must expose it even if it's not explicitly present.

As part of this, I removed the local-only implementation of AriaProperties.
While it was more complete, it's not useful to have this supported only for LocalAccessible.
In addition, it didn't expose implicit default values, which this atomic case proves we need in some cases.
We'll add more properties as needed.

Comment 5

[James Teh [:Jamie] (away returning 12 Jan)]

Attachment: Bug 1887790 part 4: Treat a live region root as a UIA control element.

Otherwise, Narrator will fail to traverse the live region when looking for its content.

Comment 6

[James Teh [:Jamie] (away returning 12 Jan)]

Attachment: Bug 1887790 part 5: Fire UIA LiveRegionChanged events.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/deee94263a33
part 1: Remove nsAccUtils::IsARIALive. r=nlapre
https://hg.mozilla.org/integration/autoland/rev/84c448c765fa
part 2: Implement the UIA LiveSetting property. r=nlapre
https://hg.mozilla.org/integration/autoland/rev/2d77157cf946
part 3: Expose aria-atomic via the UIA AriaProperties property. r=nlapre
https://hg.mozilla.org/integration/autoland/rev/b75c10fb749c
part 4: Treat a live region root as a UIA control element. r=nlapre
https://hg.mozilla.org/integration/autoland/rev/17ea92320f6b
part 5: Fire UIA LiveRegionChanged events. r=nlapre

Comment 8

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/deee94263a33
https://hg.mozilla.org/mozilla-central/rev/84c448c765fa
https://hg.mozilla.org/mozilla-central/rev/2d77157cf946
https://hg.mozilla.org/mozilla-central/rev/b75c10fb749c
https://hg.mozilla.org/mozilla-central/rev/17ea92320f6b