Yes, we do can undo an ID deletion now.
However, this requires extra care in UI 'remapping' to new IDs step
(when undoing, we do not fully reload the UI from saved .blend).
Otherwise, new UI (i.e. one from saved .blend file) might reference
IDs that where freed in old bmain (the one before the undo), we cannot
use those to get ID name then, that would be a nasty use-after-free!
To prevent this, we generate a GSet of all valid ID pointers at that
time (i.e. those found in both old and new Main's), and ensure any ID
we try to remap by its name is in that GSet. Otherwise, there is no
possible remapping, just return NULL.
BF-admins agree to remove header information that isn't useful,
to reduce noise.
- BEGIN/END license blocks
Developers should add non license comments as separate comment blocks.
No need for separator text.
- Contributors
This is often invalid, outdated or misleading
especially when splitting files.
It's more useful to git-blame to find out who has developed the code.
See P901 for script to perform these edits.
Was using O(n^2) lookup on ID's with undo.
This caused undo to hang with 1000's of data-blocks
(especially with heavy scenes & outliner-space, which doesn't even need to be visible to cause a slow-down).
Internally this uses a ghash per id-type, which is lazy-initialized.
Each key uses the name and library since there may be name collisions between libraries.
Developer Notes:
- Adds small `BKE_main_idmap_*` API.
- Needed to change linking order for this to build.
