On Wed, 4 Sep 2024 23:58:02 GMT, Harshitha Onkar <[email protected]> wrote:
>> In a JComboBox, if the user opens the dropdown list and clicks and holds the
>> down-button, then ALT-TABs to switch focus, when the user re-focuses the
>> frame with the JComboBox and opens the dropdown list again, the list will
>> still be scrolling even though the down-button isn't pressed.
>>
>> This isn't OS or L&F specific, although Aqua L&F does not have any
>> directional arrows in the dropdown list (and is thus exempt). This led me to
>> believe it could be handled in BasicComboBoxUI where focusLost and focusGain
>> are used or isPopupVisible but the scroll behavior cannot be altered here.
>> Likewise for BasicComboPopup where `autoscroll` is used. However, this
>> behavior isn't related to autoscroll and is actually found in the JScrollbar
>> of the JScrollpane inside of the JComboBox. The timer for the scroll action
>> starts but is never stopped if focus is lost, so a new listener is created
>> and used. The proposed solution uses `KeyboardFocusManager` to track the
>> focus owner. The listener stops the `scrollTimer` when the `focusOwner`
>> property is changed. With this change, the list no longer automatically
>> scrolls when re-focused and instead opens normally.
>>
>> The included test is manual due to the need to confirm that the list still
>> scrolls after ALT-TABing. The L&F is set to Metal since it is the
>> cross-platform lookandfeel and has directional buttons for the JScrollPane
>> list.
>
> src/java.desktop/share/classes/javax/swing/plaf/basic/BasicScrollBarUI.java
> line 1238:
>
>> 1236: // Stop scrolling if no longer focus owner
>> 1237: if (e.getNewValue() == null &&
>> scrollTimer.isRunning()) {
>> 1238: scrollTimer.stop();
>
> In some places `scrollTimer.stop()` is followed by
> `scrollbar.setValueIsAdjusting(false)`. Is this applicable for
> KeyboardFocusListener ?
> For instance:
> https://github.com/openjdk/jdk/blob/0cc3caf2b49426bb6738a9792c88275c0cc7774a/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicScrollBarUI.java#L1608
You're right. I added this to my fix, but didn't get it pushed yet. Thanks for
the reminder.
> test/jdk/javax/swing/JComboBox/JComboBoxScrollFocusTest.java line 59:
>
>> 57: UnsupportedLookAndFeelException, ClassNotFoundException,
>> 58: InstantiationException, IllegalAccessException, AWTException,
>> 59: InterruptedException, InvocationTargetException {
>
> Can this be simplified to throw generic Exception?
Good point.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20845#discussion_r1745789070
PR Review Comment: https://git.openjdk.org/jdk/pull/20845#discussion_r1745789363
