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

[Alexey Ivanov]

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