Fix T68852: Link select crashes after knife project

Knife project switches out of vertex selection mode, but wouldnt do this
for all participating meshes.
Logic in edbm_select_linked_pick would switch the viewcontext multiple
times and the meshes selectmode was not in sync then, leading e.g.
finding a vertex in 'unified_findnearest' (because last of the meshes
selectmode was SCE_SELECT_VERTEX), but then later in
'EDBM_elem_from_selectmode' other meshes selectmode was not matching
SCE_SELECT_VERTEX, leading to crash...

Reviewers: campbellbarton

Maniphest Tasks: T68852

Differential Revision: https://developer.blender.org/D5536

1 files changed, 16 insertions, 4 deletions

diff --git a/source/blender/editors/mesh/editmesh_knife_project.c b/source/blender/editors/mesh/editmesh_knife_project.c
index 3d34a4ad3b5..a709bd010aa 100644
--- a/source/blender/editors/mesh/editmesh_knife_project.c
+++ b/source/blender/editors/mesh/editmesh_knife_project.c
@@ -22,6 +22,7 @@
  */
 
 #include "DNA_curve_types.h"
+#include "DNA_mesh_types.h"
 #include "DNA_object_types.h"
 
 #include "BLI_math.h"
@@ -142,10 +143,21 @@ static int knifeproject_exec(bContext *C, wmOperator *op)
     /* select only tagged faces */
     BM_mesh_elem_hflag_disable_all(em->bm, BM_VERT | BM_EDGE | BM_FACE, BM_ELEM_SELECT, false);
 
-    /* not essential, but switch out of vertex mode since the
-     * selected regions wont be nicely isolated after flushing.
-     * note: call after de-select to avoid selection flushing */
-    EDBM_selectmode_disable(scene, em, SCE_SELECT_VERTEX, SCE_SELECT_EDGE);
+    CTX_DATA_BEGIN (C, Object *, ob, selected_objects) {
+      if (ob->type == OB_MESH) {
+        Mesh *me = (Mesh *)ob->data;
+        BMEditMesh *embm = me->edit_mesh;
+        if (embm) {
+          /* not essential, but switch out of vertex mode since the
+           * selected regions wont be nicely isolated after flushing.
+           * note: call after de-select to avoid selection flushing.
+           * note: do this on all participating meshes so this is in sync
+           * e.g. for later selection picking, see T68852.*/
+          EDBM_selectmode_disable(scene, embm, SCE_SELECT_VERTEX, SCE_SELECT_EDGE);
+        }
+      }
+    }
+    CTX_DATA_END;
 
     BM_mesh_elem_hflag_enable_test(em->bm, BM_FACE, BM_ELEM_SELECT, true, false, BM_ELEM_TAG);