[Bf-blender-cvs] [2d9ab46e0b6] master: Fix T77328: Crash on undo Draw Face Sets stroke with dyntopo active

[Pablo Dobarro]

Commit: 2d9ab46e0b6e417b3f9603d047c523cd7677bb20
Author: Pablo Dobarro
Date:   Wed Jun 10 01:08:35 2020 +0200
Branches: master
https://developer.blender.org/rB2d9ab46e0b6e417b3f9603d047c523cd7677bb20

Fix T77328: Crash on undo Draw Face Sets stroke with dyntopo active

Draw Face Sets does not work in Dyntopo and the sculpt API should be
responsible for that without needing to add checks all over the code,
but it was doing an undo push of type SCULPT_UNDO_FACE_SETS which is not
supported, causing the crash.

Reviewed By: sergey

Maniphest Tasks: T77328

Differential Revision: https://developer.blender.org/D7924

===================================================================

M	source/blender/editors/sculpt_paint/sculpt.c

===================================================================

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 75c88047914..84fa46e5b6b 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -5322,7 +5322,14 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush, UnifiedPaintSe
    * and the number of nodes under the brush influence. */
   if (brush->sculpt_tool == SCULPT_TOOL_DRAW_FACE_SETS && ss->cache->first_time &&
       ss->cache->mirror_symmetry_pass == 0 && !ss->cache->alt_smooth) {
-    SCULPT_undo_push_node(ob, NULL, SCULPT_UNDO_FACE_SETS);
+
+    /* Dyntopo does not support Face Sets data, so it can't store/restore it from undo. */
+    /* TODO (pablodp606): This check should be done in the undo code and not here, but the rest of
+     * the sculpt code is not checking for unsupported undo types that may return a null node. */
+    if (BKE_pbvh_type(ss->pbvh) != PBVH_BMESH) {
+      SCULPT_undo_push_node(ob, NULL, SCULPT_UNDO_FACE_SETS);
+    }
+
     if (ss->cache->invert) {
       /* When inverting the brush, pick the paint face mask ID from the mesh. */
       ss->cache->paint_face_set = SCULPT_active_face_set_get(ss);