[news.eclipse.tools] Another PropertySheetViewer bug

["Randy Hudson" <none@xxxxxxx>]

Since the PropertySheetPage is conceptually an extension to your EditPart,
we have gone through great trouble to add Undo/Redo support to it.  The undo
on our page is the same as the one on our Editor, and can undo all changes
made to the application model.  Of course, we couldn't get accelerator's to
work since that is impossible, but we do have the actions on the local
Toolbar.

From this page, selecting Undo/Redo has the potential to modify the selected
objects that were sent to the PropertySheetViewer.  When this happens, the
property sheet viewer does not update with the new selection.  The reason is
that once the PropertySheetViewer gets focus, the Part which was sending it
selection gets essentially "turned off", and cannot send further selection
events.  The PropertySheet will then hang onto the old selection
(PropertySources) which has been deleted from the model.  This can cause any
number of unexpected problems.

This problem seems to be a major flaw in the SelectionProvider model.
Really, the input to the PropertySheetViewer is another Viewer's selection,
yet simply selecting the property sheet cuts off this "feed" from the
source.  The property sheet should continue to get selection events from the
old selection provider (via the selectionService, I suppose) if it itself is
not a provider.  The same probably goes for any View in general that is
interested in the Selection service's, yet doesn't supply selection to the
SelectionService.