Add accumulated recalc flags to IDs.

Those accumulated flags get cleared every time an undo step is written
to memfile.

Preliminary work for undo-speedup.

Part of T60695/D6580.

3 files changed, 28 insertions, 1 deletions

diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index a92404b2372..1e50cda3eaf 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -703,7 +703,7 @@ void IDP_WriteProperty(const IDProperty *prop, void *wd)
   IDP_WriteProperty_OnlyData(prop, wd);
 }
 
-static void write_iddata(void *wd, const ID *id)
+static void write_iddata(WriteData *wd, ID *id)
 {
   /* ID_WM's id->properties are considered runtime only, and never written in .blend file. */
   if (id->properties && !ELEM(GS(id->name), ID_WM)) {
@@ -731,6 +731,11 @@ static void write_iddata(void *wd, const ID *id)
       }
     }
   }
+
+  /* Clear the accumulated recalc flags in case of undo step saving. */
+  if (wd->use_memfile) {
+    id->recalc_undo_accumulated = 0;
+  }
 }
 
 static void write_previews(WriteData *wd, const PreviewImage *prv_orig)
@@ -1131,6 +1136,11 @@ static void write_nodetree_nolib(WriteData *wd, bNodeTree *ntree)
   for (sock = ntree->outputs.first; sock; sock = sock->next) {
     write_node_socket_interface(wd, sock);
   }
+
+  /* Clear the accumulated recalc flags in case of undo step saving. */
+  if (wd->use_memfile) {
+    ntree->id.recalc_undo_accumulated = 0;
+  }
 }
 
 /**
@@ -2425,6 +2435,11 @@ static void write_collection_nolib(WriteData *wd, Collection *collection)
   for (CollectionChild *child = collection->children.first; child; child = child->next) {
     writestruct(wd, DATA, CollectionChild, 1, child);
   }
+
+  /* Clear the accumulated recalc flags in case of undo step saving. */
+  if (wd->use_memfile) {
+    collection->id.recalc_undo_accumulated = 0;
+  }
 }
 
 static void write_collection(WriteData *wd, Collection *collection)
diff --git a/source/blender/depsgraph/intern/depsgraph_tag.cc b/source/blender/depsgraph/intern/depsgraph_tag.cc
index b019c079dab..8decb9f6b87 100644
--- a/source/blender/depsgraph/intern/depsgraph_tag.cc
+++ b/source/blender/depsgraph/intern/depsgraph_tag.cc
@@ -814,12 +814,16 @@ void DEG_ids_check_recalc(
 
 static void deg_graph_clear_id_recalc_flags(ID *id)
 {
+  /* Keep incremental track of used recalc flags, to get proper update when undoing. */
+  id->recalc_undo_accumulated |= id->recalc;
   id->recalc &= ~ID_RECALC_ALL;
   bNodeTree *ntree = ntreeFromID(id);
   /* Clear embedded node trees too. */
   if (ntree) {
+    ntree->id.recalc_undo_accumulated |= ntree->id.recalc;
     ntree->id.recalc &= ~ID_RECALC_ALL;
   }
+  /* XXX And what about scene's master collection here? */
 }
 
 void DEG_ids_clear_recalc(Main *UNUSED(bmain), Depsgraph *depsgraph)
diff --git a/source/blender/makesdna/DNA_ID.h b/source/blender/makesdna/DNA_ID.h
index 40916cbdc61..f2923c7f144 100644
--- a/source/blender/makesdna/DNA_ID.h
+++ b/source/blender/makesdna/DNA_ID.h
@@ -245,6 +245,12 @@ typedef struct ID {
   int us;
   int icon_id;
   int recalc;
+  /**
+   * Used by undo code. Value of recalc is stored there when reading an ID from memfile, and not
+   * touched by anything, which means it can be used as 'reference' recalc value for the next undo
+   * step, when going backward (i.e. actual undo, redo can just use recalc value directly).
+   */
+  int recalc_undo_accumulated;
 
   /**
    * A session-wide unique identifier for a given ID, that remain the same across potential
@@ -252,6 +258,8 @@ typedef struct ID {
    */
   unsigned int session_uuid;
 
+  char _pad[4];
+
   IDProperty *properties;
 
   /** Reference linked ID which this one overrides. */