Fixed crash when adding/removing custom normals from pinned mesh

When a mesh is pinned in the properties panel, Blender crashes when you
click the "Add Custom Split Normals Data".

The code calls `ob = ED_object_context(C)` which returns NULL when the
mesh is pinned in the properties panel, causing a segfault when trying
to get the mesh via `ob->data`.

A new function `ED_mesh_context(C)` avoids this by first checking
whether a mesh was pinned in the context. If not, it checks the pinned
object's data. If that's not there, or it's not a mesh, it returns the
active object's mesh. Finally it returns NULL if there is no active
object, or if the active object is not a mesh object.

Reviewed By: brecht, mont29

Differential Revision: https://developer.blender.org/D5223

1 files changed, 7 insertions, 0 deletions

diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index 5fc7979a631..c9a45728bc2 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -74,6 +74,7 @@
 #include "ED_clip.h"
 #include "ED_image.h"
 #include "ED_keyframes_draw.h"
+#include "ED_mesh.h"
 #include "ED_object.h"
 #include "ED_screen.h"
 #include "ED_screen_types.h"
@@ -371,6 +372,12 @@ bool ED_operator_object_active_editable_font(bContext *C)
   return ((ob != NULL) && !ID_IS_LINKED(ob) && !ed_object_hidden(ob) && (ob->type == OB_FONT));
 }
 
+bool ED_operator_editable_mesh(bContext *C)
+{
+  Mesh *mesh = ED_mesh_context(C);
+  return (mesh != NULL) && !ID_IS_LINKED(mesh);
+}
+
 bool ED_operator_editmesh(bContext *C)
 {
   Object *obedit = CTX_data_edit_object(C);