<Swing Dev> [9] Review request for 8136998: JComboBox prevents wheel mouse scrolling of JScrollPane

[Alexander Potochkin]

Hello Alexey

The scrollerMouseWheelListener field is only initialized in the 
installScrollerListeners() method
which is called from the protected configureScroller().

So if a customer UI delegate overrides configureScroller() method,
the scrollerMouseWheelListener may not be initialized.

Could you add the null checks?

Thanks
alexp

On 5/11/2016 17:29, Alexey Ivanov wrote:
> Hello Swing team,
>
> Could you please review the fix for jdk9:
>     bug: https://bugs.openjdk.java.net/browse/JDK-8136998
>     webrev: http://cr.openjdk.java.net/~aivanov/8136998/jdk9/webrev.00/
>
>
> Problem description:
> When JComboBox is added into a JScrollPane, scroll pane is not 
> scrolled by mouse wheel if mouse over JComboBox.
>
> The fix to https://bugs.openjdk.java.net/browse/JDK-8033069 added 
> MouseWheelListener to JComboBox, and combo box consumes MOUSE_WHEEL 
> events therefore these events do not reach JScrollPane beneath JComboBox.
>
> The fix:
> Remove MouseWheelListener from JComboBox. To prevent the combo box 
> popup from being closed by rotating mouse wheel over the JComboBox, 
> MouseWheelListener is added when the popup is about to be displayed 
> and is removed when the popup is about to be hidden.
>
>
> Regards,
> Alexey