Fix T76416: Armature Deform parenting option doesn't work with Grease Pencil objects

If we parent with type `PAR_ARMATURE` (where vertexgroups are already
set up and named correctly according to the corresponding bones), we
still need an armature modifier. This just wasnt added.

In contrast to meshes [which add their armature modifier early in
`ED_object_parent_set`], grease pencil used to do this (adding the
armature modifier) in `ED_gpencil_add_armature_weights`.

Now split ED_gpencil_add_armature_weights in two:
- ED_gpencil_add_armature
- ED_gpencil_add_armature_weights (which calls ED_gpencil_add_armature)
- use ED_gpencil_add_armature for the PAR_ARMATURE case

Maniphest Tasks: T76416

Differential Revision: https://developer.blender.org/D7625

1 files changed, 16 insertions, 4 deletions

diff --git a/source/blender/editors/gpencil/gpencil_armature.c b/source/blender/editors/gpencil/gpencil_armature.c
index 1528c448c0b..ab8b1a9719b 100644
--- a/source/blender/editors/gpencil/gpencil_armature.c
+++ b/source/blender/editors/gpencil/gpencil_armature.c
@@ -481,8 +481,7 @@ static void gpencil_object_vgroup_calc_from_armature(const bContext *C,
   DEG_relations_tag_update(CTX_data_main(C));
 }
 
-bool ED_gpencil_add_armature_weights(
-    const bContext *C, ReportList *reports, Object *ob, Object *ob_arm, int mode)
+bool ED_gpencil_add_armature(const bContext *C, ReportList *reports, Object *ob, Object *ob_arm)
 {
   Main *bmain = CTX_data_main(C);
   Scene *scene = CTX_data_scene(C);
@@ -516,11 +515,24 @@ bool ED_gpencil_add_armature_weights(
       return false;
     }
   }
+  return true;
+}
+
+bool ED_gpencil_add_armature_weights(
+    const bContext *C, ReportList *reports, Object *ob, Object *ob_arm, int mode)
+{
+  if (ob == NULL) {
+    return false;
+  }
+
+  bool success = ED_gpencil_add_armature(C, reports, ob, ob_arm);
 
   /* add weights */
-  gpencil_object_vgroup_calc_from_armature(C, ob, ob_arm, mode, DEFAULT_RATIO, DEFAULT_DECAY);
+  if (success) {
+    gpencil_object_vgroup_calc_from_armature(C, ob, ob_arm, mode, DEFAULT_RATIO, DEFAULT_DECAY);
+  }
 
-  return true;
+  return success;
 }
 /* ***************** Generate armature weights ************************** */
 static bool gpencil_generate_weights_poll(bContext *C)