Sculpt: Implement undo of Apply Base during sculpt session

The idea is to push both base mesh geometry and PBVH coordinates
so it is possible to undo everything without loosing data which was
not flushed from sculpt session to base mesh.

It is possible do memory optimization to avoid push custom data
layers which are not touched by operator, but before doing that
better to ensure this is a correct and working approach.

Differential Revision: https://developer.blender.org/D7381

1 files changed, 93 insertions, 1 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_undo.c b/source/blender/editors/sculpt_paint/sculpt_undo.c
index 340f7191b95..c07ebf790d4 100644
--- a/source/blender/editors/sculpt_paint/sculpt_undo.c
+++ b/source/blender/editors/sculpt_paint/sculpt_undo.c
@@ -55,6 +55,9 @@
 #include "BKE_subsurf.h"
 #include "BKE_undo_system.h"
 
+// XXX: Ideally should be no direct call to such low level things.
+#include "BKE_subdiv_eval.h"
+
 #include "DEG_depsgraph.h"
 
 #include "WM_api.h"
@@ -552,7 +555,9 @@ static void sculpt_undo_geometry_free_data(SculptUndoNodeGeometry *geometry)
 
 static void sculpt_undo_geometry_restore(SculptUndoNode *unode, Object *object)
 {
-  SCULPT_pbvh_clear(object);
+  if (unode->geometry_clear_pbvh) {
+    SCULPT_pbvh_clear(object);
+  }
 
   if (unode->applied) {
     sculpt_undo_geometry_restore_data(&unode->geometry_modified, object);
@@ -740,6 +745,10 @@ static void sculpt_undo_restore_list(bContext *C, Depsgraph *depsgraph, ListBase
     }
   }
 
+  if (subdiv_ccg != NULL) {
+    BKE_subdiv_eval_refine_from_mesh(subdiv_ccg->subdiv, ob->data, NULL);
+  }
+
   if (update || rebuild) {
     bool tag_update = false;
     /* We update all nodes still, should be more clever, but also
@@ -1079,6 +1088,7 @@ static SculptUndoNode *sculpt_undo_geometry_push(Object *object, SculptUndoType
 {
   SculptUndoNode *unode = sculpt_undo_find_or_alloc_node_type(object, type);
   unode->applied = false;
+  unode->geometry_clear_pbvh = true;
 
   SculptUndoNodeGeometry *geometry = sculpt_undo_geometry_get(unode);
   sculpt_undo_geometry_store_data(geometry, object);
@@ -1510,3 +1520,85 @@ static UndoSculpt *sculpt_undo_get_nodes(void)
 }
 
 /** \} */
+
+/* -------------------------------------------------------------------- */
+/** \name Undo for changes happening on a base mesh for multires sculpting.
+ *
+ * Use this for multires operators which changes base mesh and which are to be
+ * possible. Example of such operators is Apply Base.
+ *
+ * Usage:
+ *
+ *   static int operator_exec((bContext *C, wmOperator *op) {
+ *
+ *      ED_sculpt_undo_push_mixed_begin(C, op->type->name);
+ *      // Modify base mesh.
+ *      ED_sculpt_undo_push_mixed_end(C, op->type->name);
+ *
+ *      return OPERATOR_FINISHED;
+ *   }
+ *
+ * If object is not in sculpt mode or sculpt does not happen on multires then
+ * regular ED_undo_push() is used.
+ * *
+ * \{ */
+
+static bool sculpt_undo_use_multires_mesh(bContext *C)
+{
+  if (BKE_paintmode_get_active_from_context(C) != PAINT_MODE_SCULPT) {
+    return false;
+  }
+
+  Object *object = CTX_data_active_object(C);
+  SculptSession *sculpt_session = object->sculpt;
+
+  return sculpt_session->multires.active;
+}
+
+static void sculpt_undo_push_all_grids(Object *object)
+{
+  SculptSession *ss = object->sculpt;
+  PBVHNode **nodes;
+  int totnodes;
+
+  BKE_pbvh_search_gather(ss->pbvh, NULL, NULL, &nodes, &totnodes);
+  for (int i = 0; i < totnodes; i++) {
+    SculptUndoNode *unode = SCULPT_undo_push_node(object, nodes[i], SCULPT_UNDO_COORDS);
+    unode->node = NULL;
+  }
+
+  MEM_SAFE_FREE(nodes);
+}
+
+void ED_sculpt_undo_push_multires_mesh_begin(bContext *C, const char *str)
+{
+  if (!sculpt_undo_use_multires_mesh(C)) {
+    return;
+  }
+
+  Object *object = CTX_data_active_object(C);
+
+  SCULPT_undo_push_begin(str);
+
+  SculptUndoNode *geometry_unode = SCULPT_undo_push_node(object, NULL, SCULPT_UNDO_GEOMETRY);
+  geometry_unode->geometry_clear_pbvh = false;
+
+  sculpt_undo_push_all_grids(object);
+}
+
+void ED_sculpt_undo_push_multires_mesh_end(bContext *C, const char *str)
+{
+  if (!sculpt_undo_use_multires_mesh(C)) {
+    ED_undo_push(C, str);
+    return;
+  }
+
+  Object *object = CTX_data_active_object(C);
+
+  SculptUndoNode *geometry_unode = SCULPT_undo_push_node(object, NULL, SCULPT_UNDO_GEOMETRY);
+  geometry_unode->geometry_clear_pbvh = false;
+
+  SCULPT_undo_push_end();
+}
+
+/** \} */