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
ClutterCanvas is a ClutterContent interface implementation; this means
that it can be created and modified regardless of whether it is
associated to a specific actor or a stage. For this reason, we cannot
walk the hierarchy and get the window scaling factor for high DPI
density displays out of the ClutterStage when we create the Cairo
surface that we will use to draw the canvas contents on.
We can use ClutterSettings:window-scaling-factor instead, since it's
what each ClutterStage will use anyway.
This will get slightly more complicated when we support per-output
window scaling factors (like on Wayland), but that will require changes
in the entire settings architecture anyway.
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().
The example code that is meant to be XIncluded into the API reference
should not be part of the interactive test suite: it's code that it is
meant to be used as a reference implementation - whereas the interactive
test suite should be allowed to be lean and test behaviour even in nasty
ways. In short: the test suite should not be the place where we show off
idiomatic code for educational purposes.
The ClutterCanvas content implementation should be used instead, to
avoid stringing along the ClutterTexture API and implementation.
This change requires some minor surgery, as the deprecated section
already contains an header for the previously deprecated methods; plus,
we don't want to deprecate clutter_cairo_set_source_color(). This means
creating a new header to be used for Cairo-related API.
This also avoids the warning
Cogl-WARNING **: ./cogl-buffer.c:215: GL error (1285): Out of memory
generated by cogl_buffer_map when the CoglBuffer has zero length.
Both ClutterCanvas and ClutterImage should use the minification and
magnification filters set on the actor, just like the use the content
box and the paint opacity.
