We want to be able to map any window coordinate to a root coordinate, not
just the origin, because you can't rely anymore on a simple translation
from window coordinates to parent with offscreen windows. This lets
us e.g. pop up menus in the right place even if they are popped up from
a no-window widget.
We use the offscreen signals for getting parent, picking
children at a point and mapping coordinates between windows
embedding offscreens and offscreens.
This means we have two hierarchies more or less, one visible to apps via
the standard APIs and for drawing where the offscreens are their own
separate toplevels, and another one for event handling where embedded
offscreens appear as if they were children of the embedding window.
3 signals are for offscreen windows
get-offscreen-parent: Get the parent window an offscreen is embedded in
to-parent: Convert coordinates from offscreen to parent
from-parent: Convert coordinates from parent to offscreen
1 signal is for the window embedding offscreens:
pick-offscreen-child: This picks what (if any) offscreen is at a specific position
The last signal is only used if you call gdk_window_set_has_offscreen_children
to tell gdk that the window has embedded offscreen children.
Add get-pointer signal for offscreen window pointer getting
Apps using offscreen windows can connect to get-pointer on offscreen
windows in order to make gdk_window_get_pointer() return correct
values.
Add get-offscreen-parent signal
Add signals for from-parent and to-parent coordinate mapping
Add pick-offscreen-child signal
In the new world offscreen windows are not put in the hierarchy, but are
rather toplevels for themselves. Offscreen hooks don't make any sense
in this model.
The history before this was kind of twisted as several different
approaches were tested, so that was all squashed into this initial
commit to hide the uninteresting changes and files that were later
removed.
