On Wed, 4 Sep 2024 00:54:16 GMT, Damon Nguyen <[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
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?
test/jdk/javax/swing/JComboBox/JComboBoxScrollFocusTest.java line 85:
> 83: return frame;
> 84: }
> 85: }
EOF newline missing here
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20845#discussion_r1744633549
PR Review Comment: https://git.openjdk.org/jdk/pull/20845#discussion_r1744612747
PR Review Comment: https://git.openjdk.org/jdk/pull/20845#discussion_r1744613060
