While most compositors handle instantiated but not-yet-mapped
sub-surfaces correctly, e.g. kwin does not.
For example, it will incorrectly offset the main surface both
horizontally and vertically with a couple of pixels, leaving two
transparent areas at the top and left, between the SSDs and the main
surface.
Note that a workaround is to position the sub-surfaces inside the main
surface while they're unmapped. However, since the surfaces may be
larger than the main surface (the CSDs, for examples, always are),
this doesn't quite work since kwin, at least, resizes the window to
include the sub-surfaces, even when unmapped.
So, instead we instantiate all sub-surfaces on demand, when we know
where to position them, and when they should be mapped.
For now, this behavior is controlled with an ifdef. At least kwin
seems very buggy when the decorations are positioned like this (but
normally you'd use server-side decorations with kwin anyway).
This commit also changes 'use_csd' to be a tri-state variable;
when instantiating a window it is set to 'unknown'.
If there's no decoration manager available (e.g. weston), we
immediately set it to 'yes' (use CSDs).
Otherwise, we wait for the decoration manager callback to indicate
whether we should use CSDs or not.
We draw the CSDs in a darker color when we're inactive.
Weston seems to be buggy with synchronized subsurfaces, so temporarily
reconfigure them to desynchronized surfaces.
It seems kwin expects a wl_surface_commit() for each
xdg_surface_ack_configure().
We don't want to commit before we've rendered a resized surface. So,
if we *did* change the window size, let the normal rendering path do
the surface commit.
Only when we did *not* change the window size do we need to explicitly
commit the surface in xdg_surface_configure().
Call render_resize_force() when the decoration type changes
run-time. This ensures the CSDs are drawn when changing from server ->
client side decorations, and removed when going the other way.
This is needed to handle pointer motion and button events correctly,
since mouse actions in e.g. CSD surfaces are very different from mouse
actions in the main window.
