SHORT SUMMARY:

No Horizontal Mouse Wheel Support In BasicScrollPaneUI

DESCRIPTION:

May need to be broken out into two RFEs

Problem 1:
Few mouse like Apple Mighty Mouse and Trackpads support horizontal scrolling
through its wheel and with a magin mouse, horizontal wheel scrolling can be
done in Windows as well. But there appears to be no support in
MouseWheelEvent to determine horizontal or vertical scrolling. This prevents
us/scrollpane ui in providing such support

Problem 2:
Even if there is no in-built horizontal wheel scrolling through mouse, there
should be a way to do horizontal wheel scrolling (not clicking and dragging
horizontal scroll bar) in Java ScrollPane. With the following code in
BasicScrollPaneUI:

            if (scrollpane.isWheelScrollingEnabled() &&
                e.getWheelRotation() != 0) {
                JScrollBar toScroll = scrollpane.getVerticalScrollBar();
                int direction = e.getWheelRotation() < 0 ? -1 : 1;
                int orientation = SwingConstants.VERTICAL;

                // find which scrollbar to scroll, or return if none
                if (toScroll == null || !toScroll.isVisible()) {
                    toScroll = scrollpane.getHorizontalScrollBar();
                    if (toScroll == null || !toScroll.isVisible()) {
                        return;
                    }
                    orientation = SwingConstants.HORIZONTAL;
                }

the horizontal wheel scrolling is enabled only when vertical scrollbar is not
present. There should be a way to use some modifier like SHIFT/CTRL along
with mouse wheel scrolling to enable horizontal scrolling. For example Google
Chrome does this.