8377936: VoiceOver Reads Button Incorrectly

[mickleness]

With this PR:
We call CAccessible.valueChanged when we believe the value changed, not when the AccessibleStateSet changed.

Although this is a small refactor: it touches parts of code that span approximately a decade of different bug fixes. At least one of these older bugs was a P2. I tried to note the related issues in the test for reference. (Also in my testing I confirmed JRadioButtons and JToggleButtons work as expected, but I kept the final test simple for the convenience of human testers.)

In 8377936 the problem was:

We had two components, X and Y. When VO transferred the focus from X to Y, it would (ever so briefly) start to announce Y.** Then Swing would update X's AccessibleContext to inform it that X was no longer focused, therefore X's AccessibleStateSet changed. This triggered CAccessible's AXChangeNotifier, which called CAccessible.valueChanged. This resulted in VoiceOver announcing X's state (as if it thought the selected state changed), even though the keyboard focus was now on Y.

The AXChangeNotifier was probably intending to call valueChanged only when AccessibleState.SELECTED or CHECKED or something important was updated. The fact that it called valueChanged for AccessibleState.FOCUSED is probably an oversight***.

** If you comment out the line in CAccessibility.requestFocus that actually requests the focus: then VoiceOver announced Y correctly. But this left the keyboard focus on the wrong component.

*** I also tested triggering AccessibleState.FOCUSABLE, AccessibleState.VISIBLE, and a few other states; none of them resulted in a comparable bug, though.

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Issue

• JDK-8377936: VoiceOver Reads Button Incorrectly (Bug - P5)

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