We need to provide an escape hatch to ClutterCanvas so that it's
possible to override the window-scaling-factor ClutterSetting. This is
going to be useful in the future in case the user has better knowledge
of the window scaling factor that is going to be used with a specific
set of ClutterCanvas contents (e.g. on different outputs or stages).
https://bugzilla.gnome.org/show_bug.cgi?id=705915
Currently, clutter_canvas_set_size() causes invalidation of the canvas
contents only if the newly set size is different. There are cases when
we want to invalidate the content regardless of the size set, but we
cannot do that right now without possibly causing two invalidations,
for instance:
clutter_canvas_set_size (canvas, new_width, new_height);
clutter_content_invalidate (canvas);
will cause two invalidations if the newly set size is different than
the existing one. One way to work around it is to check the current
size of the canvas and either call set_size() or invalidate() depending
on whether the size differs or not, respectively:
g_object_get (canvas, "width", &width, "height", &height, NULL);
if (width != new_width || height != new_height)
clutter_canvas_set_size (canvas, new_width, new_height);
else
clutter_content_invalidate (canvas);
this, howevere, implies knowledge of the internals of ClutterCanvas,
and of its optimizations — and encodes a certain behaviour in third
party code, which makes changes further down the line harder.
We could remove the optimization, and just issue an invalidation
regardless of the surface size, but it's not something I'd be happy to
do. Instead, we can add a new function specifically for ClutterCanvas
that causes a forced invalidation regardless of the size change. If we
ever decide to remove the optimization further down the road, we can
simply deprecate the function, and make it an alias of invalidate()
or set_size().
