441a440cbb
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.