I have implemented a scroll pane UI that simulates the modern OS X scroll bars that are painted over the viewport rather than occupying their own space in the scroll pane. Overlaying the scroll bars requires that the scroll pane return false from isOptimizedDrawingEnabled(). However, JScrollPane.isOptimizedDrawingEnabled() is hardwired to return true. Although subclassing JScrollPane is a workaround, it is not a good solution, because it breaks the orthogonality of component and component UI. It would mean, for example, that a UI created using the NetBeans UI designer could not use overlay scroll bars.
Another workaround I have thought of but am reluctant to pursue is to install a custom viewport that paints the scroll bars. Given the general ability of a component UI to install a layout manager, it strikes me as odd that isOptimizedDrawingEnabled() is not implemented as an attribute, as it is in JLayeredPane. Is there a reason for this? Any suggestions? Alan
