MetaWindowActor: Fix crashes when mapping and unmapping windows
The assumptions made when getting the size of the window for the
paint volume turned out not to be accurate in all cases -
get_paint_volume() could be called on windows without computed
bounds.
Fullscreen and maximized windows never have visible shadows - the only
case where we would ever see them is if they bleed onto an adjacent
monitor and that looks bad.
It's small performance win to avoid computing them, and this also avoids
painting the top shadow for all maximized windows in GNOME Shell - since
the top panel isn't a X window, it doesn't factor into the computation
of what parts of windows are visible and maximized windows are computed
as having a top shadow.
Add meta_window_get_maximized() and meta_window_is_fullscreen()
These functions duplicate existing properties; they are added for
convenience and to avoid the GObject property code on some
performance critical painting paths.
Implement more accurate clipping of obscured shadows
Instead of making optimizing obscured shadows an all-or-none operation,
pass the clip region to meta_shadow_paint() and only paint the 9-slices
that are at least partially visible.
Instead of setting shadow parameters on individual windows, add the
idea of a "shadow class". Windows have default shadow classes based
on their frame and window type, which can be overriden by setting
the shadow-class property.
Each shadow class has separably configurable parameters for the
focused and unfocused state. New shadow classes can be defined with
arbitrary names.
