RFR: 8348936: [Accessibility,macOS,VoiceOver] VoiceOver doesn't announce untick on toggling the checkbox with "space" key on macOS

[Abhishek Kumar]

On Tue, 4 Feb 2025 13:24:29 GMT, Artem Semenov <asemenov at openjdk.org> wrote:

>> VoiceOver doesn't announce the _untick state_ when Checkbox is `deselected` using **space** key. When CheckBox is deselected, the state change is not notified to a11y client (VoiceOver) and so the state is not announced by VO. 
>> 
>> Screen Magnifier is also unable to magnify the unchecked state of JCheckBox due to same reason and is captured as separate bug [JDK-8345728](https://bugs.openjdk.org/browse/JDK-8345728).
>> 
>> Proposed fix is to send the state change notification to a11y client when checkbox is deselected, this resolves the problem for VoiceOver and Screen Magnifier.
>> 
>> Similar issue observed for JToggleButton. So, I extended the fix for JToggleButton as well.
>> 
>> The proposed change can be verified the manual test in the PR.
>> 
>> CI pipeline testing is `OK`, link posted in JBS.
>
> src/java.desktop/macosx/classes/sun/lwawt/macosx/CAccessible.java line 186:
> 
>> 184:                     if (thisRole == AccessibleRole.CHECK_BOX) {
>> 185:                         if ((newValue != null && !newValue.equals(oldValue)) ||
>> 186:                                 oldValue != null && !oldValue.equals(newValue)) {
> 
> At first glance, these conditions look like the same thing. equals() above will return false if oldValue is null. oldValue.equals(newValue) and newValue.equals(oldValue) are also the same thing. Try to rewrite this condition more clearly.

When CheckBox state is `checked`, `newValue is Checked` and `oldValue is null` and the existing condition `if (newValue != null && !newValue.equals(oldValue))` works well. But when CheckBox is `unchecked`, `newValue is null` and `oldValue is checked`, the existing condition returns `false` when `newValue != null` is evaluated.

oldValue.equals(newValue) and newValue.equals(oldValue) looks same but when newValue is null, newValue.equals(oldValue) throws NPE.

So, I think these conditions are not exactly same. We need to evaluate the `oldValue!=null` when CheckBox is unchecked for the correct behaviour.

@aivanov-jdk suggested simpler way for comparing oldValue and newValue [here](https://github.com/openjdk/jdk/pull/23436#discussion_r1941484674). I will check and update.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23436#discussion_r1942299553