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.
and use it to set visibility of guides and sample points, so this
reression is fixed.
- return NULL extents for invisible items and never draw them
- do nothing for invisible items in more places, like the group
While hacking this, it turned out that it was a braino to collect an
item's region before and after a change in
dispatch_properties_changed(), so a new update had to be devised:
- add a "change count" and new API begin_change()/end_change()
- in begin_change(), remember the item's extents before the change
- in end_change(), combine old and current extents and emit "update"
- add some protected function to emit "update", and to figure if
it makes sense at all to emit "update" on an item.
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
In order to avoid visually overlapping lines:
- GimpCanvasItem got a "suspend_stroking" API that allows to skip
stroking and instead starts a new sub-path
- GimpCanvasGroup got a "group_stroking" API that sets suspend_stroking
on all its children and does one stroke after calling all items'
draw().
