Fix double speaking label in angular checkbox

[feerrenrut]

Link to issue number:

https://bugs.chromium.org/p/chromium/issues/detail?id=995603

Summary of the issue:

The HTML for checkboxes on https://dart-lang.github.io/angular_components/#/material_checkbox have aria-labelledby pointing to a sub-element of the checkbox. Normally, we announce the accessible name as we descend then read the child elements. This results in double speaking the name.

Description of how this pull request fixes the issue:

When rendering the virtual buffer, track the ID's of the nodes. If this node has a label, check if the ID for the label node matches any sub-node then set an attribute labelledByContents. Then in speech.py don't speak the name for a controlField if it has this attribute.

Testing performed:

Simplified test case:

data:text/html,<button>begin</button><div tabindex="0" role="checkbox" aria-labelledby="inner-label"><div style="display:inline" id="inner-label">Simulate evil cat</div></div>

Known issues with pull request:

Change log entry:

Section: New features, Changes, Bug fixes

[michaelDCurran]

I don't quite get what parentIDs does? I get that outIds stores all descendant IDs, and that if the labelledID appears in the list, then you mark it as the label coming from content.
An out of the box idea though:
Since the buffer already stores nodes by ID, rather than using your own ID lists, why not just make use of what the buffer has already. So call GetControlfieldNodeByIdentifier with the label ID, once before all the possible recursions, and then once after, at the end. If a node did not exist before, but does after, than the node is a descendant. Note that getControlFieldNodeByIdentifier is very cheep as it itself just looks up the ID in a map.

[feerrenrut]

I don't quite get what parentIDs does?

While developing this I wasn't sure if I would need to check parent ID's on the child side, and left it in for the symmetry.

I see what you are suggesting, with getControlFieldNodeWithIdentifier, it's a clever approach, but I think it makes the code harder to maintain, since it implicitly depends on how that map is built. Though, looking at how that map is built (via the calls to addControlFieldNode), in the same place I'll build an ID tree.

[maniekins]

I noticed, the aria-labelledby is not working with inner elements after 2019.3 version and it is probably related with this changes. I tested example 2 from https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_aria-labelledby_attribute , added some button next to header, and when we are focusing on that button, main is vocalized but without h1 label.