Java project diagram doesn't show

[hallvard]

When dragging a package from the Package or Project Explorer to the PlantUML Project Class Diagram, nothing is shown.

[hallvard]

This happens because the view things it's invisible! Since that view isn't linked to the the active part it doesn't attach a PartListener, and hence never gets a notification that sets it's visible flag. The flag should be set when the drop is handled, since then it's obviously visible.