ClutterTexture is full of side effects that have been picked up over the
years; they make improving ClutterTexture harder than necessary, as well
as making subclassing impossible without introducing weird behaviours in
the child classes as well.
Since Clutter 1.10 we have the ClutterImage content type, which is
side-effects free, given that it just paints texture data using the
state of the actor.
Sadly, we still have subclasses of ClutterTexture, both deprecated and
not, so we cannot deprecate ClutterTexture right out; the type and
structures will still be available, like we do for ClutterGroup, but the
whole API should be moved to the deprecated section, waiting for the
time in which we can get rid of it all.
Previously, the Cogl backend was at times a subclass of the X11
backend, and at times a standalone one. Now it is the other way
round, with GDK and X11 backends providing the concrete classes,
layered on top of the generic Cogl backend. A new EglNative backend
was introduced for direct to framebuffer rendering. This greatly
simplifies the API design (at the expense of some casts needed)
and reduces the amount of #ifdefs, without duplicating code.
https://bugzilla.gnome.org/show_bug.cgi?id=657434
