There is now a preference option that determines whether windows
should be opened on the same monitor as before. It should be disabled
when the machine gets monitors plugged/unplugged dynamically ("laptop")
and enabled when there is a static multi-monitor setup ("wokstation").
This is merely the current simplistic policy on top of the newly added
underlying infrastructure:
- pass integer monitor numbers around in all places where we already
pass around a GdkScreen. Pass the "current" monitor to these changed
APIs, where "current" is either the monitor where the action-triggering
widget is, or if that is unavailable the monitor where the mouse is.
- add gimp_widget_get_monitor() in order to easily get to the monitor,
just like gtk_widget_get_screen().
- add screen and monitor parameters in some places that were missed
before.
- in sessionrc, save all window positions relative to the window's
monitor, and save the monitor separately, if it's not the screen's
primary monitor.
- when restoring window positions, use the stored monitor when the new
prefs options says so (use the screen's primary monitor if there is
no stored monitor), otherwise use current monitor that is now passed
around.
Also make some of GimpToolGui's memory management proper, there was
no leak but it needs to be proper in order to add runtime switching
between dialog and overlay.
