Cut down on boilerplate by using the (no longer that) new helper
macros. We don't care about breaking ABI in private libraries, so
use G_DECLARE_FINAL_TYPE even where the class struct used to be
exposed in the header, except for types we inherit from ourselves
(obviously) or where the class exposes any vfuncs (where changes
could affect inheritance in extensions).
Base ShellStack on StContainer rather than ClutterGroup, so that it
has StWidget-y features (and so we don't have to "cheat" in
shell_stack_allocate()). Implement navigate_focus() to only ever pass
focus into the top-most child, since doing otherwise would be
surprising.
https://bugzilla.gnome.org/show_bug.cgi?id=646934
ShellDrawingArea is a size-independent wrapper for a ClutterCairoTexture.
Useful when drawing non-fixed size areas.
ShellStack is a simple container class which holds items
in a completely overlapping Z stack. The main difference
from ClutterGroup is that items will be constrained to
(and allocated) the size of the stack, not getting their
preferred size always.
