Add experimental global undo speedup.

The feature is hidden behind an experimental option, you'll have to
enable it in the preferences to try it.

This feature is not yet considered fully stable, crashes may happen, as
well as .blend file corruptions (very unlikely, but still possible).

In a nutshell, the ideas behind this code are to:
* Detect unchanged IDs across an undo step.
* Reuse as much as possible existing IDs memory, even when its content
  did change.
* Re-use existing depsgraphs instead of building new ones from scratch.
* Store accumulated recalc flags, to avoid needless re-compute of things
  that did not change, when the ID itself is detected as modified.

See T60695 and D6580 for more technical details.

1 files changed, 9 insertions, 3 deletions

diff --git a/source/blender/blenloader/intern/readblenentry.c b/source/blender/blenloader/intern/readblenentry.c
index a4b96c9e59c..085e500f7e5 100644
--- a/source/blender/blenloader/intern/readblenentry.c
+++ b/source/blender/blenloader/intern/readblenentry.c
@@ -363,17 +363,17 @@ BlendFileData *BLO_read_from_memory(const void *mem,
 BlendFileData *BLO_read_from_memfile(Main *oldmain,
                                      const char *filename,
                                      MemFile *memfile,
-                                     eBLOReadSkip skip_flags,
+                                     const struct BlendFileReadParams *params,
                                      ReportList *reports)
 {
   BlendFileData *bfd = NULL;
   FileData *fd;
   ListBase old_mainlist;
 
-  fd = blo_filedata_from_memfile(memfile, reports);
+  fd = blo_filedata_from_memfile(memfile, params, reports);
   if (fd) {
     fd->reports = reports;
-    fd->skip_flags = skip_flags;
+    fd->skip_flags = params->skip_flags;
     BLI_strncpy(fd->relabase, filename, sizeof(fd->relabase));
 
     /* clear ob->proxy_from pointers in old main */
@@ -384,6 +384,12 @@ BlendFileData *BLO_read_from_memfile(Main *oldmain,
     /* add the library pointers in oldmap lookup */
     blo_add_library_pointer_map(&old_mainlist, fd);
 
+    if ((params->skip_flags & BLO_READ_SKIP_UNDO_OLD_MAIN) == 0) {
+      /* Build idmap of old main (we only care about local data here, so we can do that after
+       * split_main() call. */
+      blo_make_old_idmap_from_main(fd, old_mainlist.first);
+    }
+
     /* makes lookup of existing images in old main */
     blo_make_image_pointer_map(fd, oldmain);