Timelines and Logic Editors are gone. So far they were simply replaced by broken
Info Editors, now they are replaced by Dopesheets in the new Timeline mode.
We reuse ScrArea.butspacetype to temporarily store the space-type identifier of
the deprecated editor (see 9db492de6d). That way we can identify it in
versioning code and replace it nicely.
Action editor creation needs a scene to set the scrolling based on frame range.
Active screen-layouts use the active scene of the window they are displayed in.
Inactive screens simply use the first scene in the main data base.
Note that inactive editors don't need version patching, readfile.c converts them
to SPACE_EMPTY already, so users can't activate them.
Files saved since the editors were removed will still be broken.
Workspace config files saved before this will also crash (will update default
one in followup commit).
The only real reason we need `butspacetype` is while switching areas, where we
need to delay the actual switch to the RNA _update callback since only there we
can access context.
So instead of trying to sync it with `spacetype`, only set while needed and
unset it afterwards (as in set to `SPACE_EMPTY`).
This should also allow us to re-use `butspacetype` in versioning code when
trying to read removed editors. It'll store the space type value of the removed
editor which we can then use on versioning.
For backwards compatibility, we store `butspacetype` with the value of
`spacetype`.
This makes easier to distinguish between different editors
(as oppose to an editor and its regions).
Note action zones look a bit strange with this. I recommend we do next:
* Make sure all 4 corners can be used as action zones.
* Remove their drawing code (or show them only on mouse hover).
- UILayout.popover(.. panel_type ..)
A single panel
- UILayout.popover_group(.. panel categories ..)
Expands all panels matching args.
Currently used in the topbar for redo and paint options.
Requiring context means we can't easily create new editors to replace deprecated
ones in versioning code.
Think it's reasonable to give editors access to scene and area data for their
initial setup though. They mostly need it for setting "the view", as in,
scrolling values.
Also did minor cleanup in top-bar creation function.
Steps to recreate were:
* Create custom transform orientation.
* Change properties editor into 3D View.
* Trigger refresh of 3D view header by mouse hovering it.
Mistake in rB7d055da327b9555f.
