Description trevor campbell 2005-04-03 20:05:00 EDT

I have an aplication that shows a map and pops up a tooltip when the cursor
passes over a place on the map and shows the location description.

In MS Windows this behaves as expected, but in Linux GTK2 a number of things go
funny.  These may be GTK problems rather than SWT problems, I don't know.
1/ The tooltip shows below the control (not below the mouse pointer) If the
control (a canvas) is in a ScrolledComposite then the tooltip is at the bottom
of the canvas, which can be almost anywhere depending on the scrolled position.
2/  Setting the tooltip to null  ( _composite.setToolTipText(""); ) or an empty
string stops the tooltip from working until the mouse leaves and reenters the
control.  
Normally if the mouse hovers over the map ( canvas ) I set the tooltip to the
name of the place on the map and if the mouse hovers over an empty region I set
the tooltip to null.  This works in windows but not at all well in Linux-GTK.

Sample code follows

_canvas = new Canvas(_composite, SWT.NONE);
_composite.setContent(_canvas);
(other initialisation stuff ) 
_canvas.addMouseTrackListener(new MouseTrackAdapter() {
            public void mouseHover(MouseEvent e) {
                for (Point p : _wayPoints.keySet()) {
                    if (Math.abs(p.x - e.x) < 5 && Math.abs(p.y - e.y) < 5) {
                        Waypoint wp = _wayPoints.get(p);
                        _composite.setToolTipText(wp.getName());
			return;
                    }
                }
                _composite.setToolTipText("");
            }
        });