This commit affects:
* Reading undo steps from memfile (aka 'Global Undo');
* Handling of UI IDs (WindowManager, Workspaces and Screens) when
opening a .blend file.
While no major changes are expected from a user PoV, there may be some
unexpected changes in rare edge-cases. None has been identified so far.
Undo step loading should be marginally faster (`setup_app_data` itself
is 2-3 times faster, as it does not do remapping anymore, which makes the
whole 'read undo step' process about 20% faster - but the most
time-consuming step on undo is the depsgraph processing, which remains
unchanged here).
This commit also solves some bugs (crashes) in some relatively uncommon
cases, like e.g. if the WM had an IDProperty pointing at an object and
UI is not loaded when opening a new .blend file with the 'Load UI' option
enabled (as in previous code on file opening WM ID would never be
remapped).
From a more technical side, this commit aims mainly at cleaning things
up, in preparation for the introduction of new 'no undo, no readfile'
type of handling (as part of the Brush Assets project):
- Prevent WM code from doing (too much) horrible ID 'management' on
its WM when opening a new file. It used to remove current WM from
the Main database, store it in a temporary own list, and then free
it itself...
- Trying to make the complex logic behind WM handling on file reading a
bit more easy to follow, at least way more documented in code.
- Keep the handling of 'IDs being re-used from old Main' in a single
place, as much as possible:
-- Readfile code itself in undo case (because it's more efficient,
and undo case is in a way simpler than actual .blend file
reading case). The whole `blo_lib_link_restore` block of code
is also removed.
-- (Mostly) setup_app_data code in actual file reading case.
- Sanitize the usage of the 'libmap' in readfile code in undo case
(waaaaay too many pointers were added there, which was hiding some
other issues in the related code, and potentially causing (in
rare cases) memory addresses collisions.
Bastien Montagne