Revert all the work that happened on the master branch.
Sadly, this is the only way to merge the current development branch back
into master.
It is now abundantly clear that I merged the 1.99 branch far too soon,
and that Clutter 2.0 won't happen any time soon, if at all.
Since having the development happen on a separate branch throws a lot of
people into confusion, let's undo the clutter-1.99 → master merge, and
move back the development of Clutter to the master branch.
In order to do so, we need to do some surgery to the Git repository.
First, we do a massive revert in a single commit of all that happened
since the switch to 1.99 and the API version bump done with the
89a2862b05 commit. The history is too long
to be reverted commit by commit without being extremely messy.
At least for the time being, we only expose the parts of the API that we
want to use internally and for new, out-of-tree Content implementations.
The full PaintNode tree API will be made public in 1.12 once we branch
master.
Now that we have a proper scene graph API, we should split out the
rendering part from the logical and event handling part.
ClutterPaintNode is a lightweight fundamental type that encodes only the
paint operations: pipeline state and geometry. At its most simple, is a
way to structure setting up the programmable pipeline using a
CoglPipeline, and submitting Cogl primitives. The important take away
from this API is that you are not allowed to call Cogl API like
cogl_set_source() or cogl_primitive_draw() directly.
The interesting approach to this is that, in the future, we should be
able to move to a purely retained mode: we will decide which actors need
to be painted, they will update their own branch of the render graph,
and we'll take the render graph and build all the rendering commands
from that.
For the 1.x API, we will have to maintain invariants and the existing
behaviour, but as soon as we can break API, the old paint signal will
just go away, and Actors will only be allowed to manipulate the render
tree.
