This is a gross hack that typedefs around between GdkRegion and
cairo_region_t and has some evil #ifdefs. This is going to die
immeditately once we can depend on cairo 1.10.
which gets emitted when the item wants to be redrawn:
- Emit "update" it when any item property changes
- Groups connect to their children and forward "update" for them
- The shell connects to its group of canvas items and exposed
the affected area
- Remove gimp_display_shell_expose_item()
- Move all the shell's item group code into gimpdisplayshell-items.c
Michael Natterer