Hi,
I noticed the trail marks disappear, after the mouse movement. Also the JComponent.setBounds() method API says "This method changes layout-related information, and therefore,
invalidates the component hierarchy." which doesn't happen as soon as the sliding panel moves to the new location. Though I don't understand why there is a delay in invalidating the component hierarchy, it made easy to get a workaround. Calling repaint() manually as shown below, fixes the problem. Hope this helps.