[NETBEANS-5756] Wheel Scrolling broken from 8.2

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 12.4
• Component/s: ide - UI
• Assignee: Unassigned
• Reporter: Nicolas Gouteux
• Created: 06/Jun/21 17:20
• Updated: 06/Jun/21 17:20

Description

In 8.2, the UI was using BasicScrollPaneUI
the handler of mouse wheel was returning if viewport was null

JViewport vp = scrollpane.getViewport();
if (vp == null) { return; }

In later versions, you introduced SmoothScrollPaneUI
the handler of mouse wheel was returning if viewport is null
but also if the instance is not Scrollable:

JViewport viewport = this.scrollpane.getViewport();
if (viewport != null && viewport.getView() instanceof Scrollable) {

As a result, the wheel stop to function on non scrollable components
Whereas it used to work in the past, as if component was not scrollable it went to

else {
// Viewport's view is not a Scrollable, or fast wheel
// scrolling is not enabled.
BasicScrollBarUI.scrollByUnits(toScroll, direction,
units, limitScroll);
}

To avoid this regression, Netbeans code should mimic default swing behavior which is to scroll even if viewport's view is not a Scrollable.