fix/workaround [#31811] Subdivision Surface (Apply modifier to editing cage during Editmode) Loop Cut Crash

A correct fix for this bug likely involves changuing how operators are called in the event loop but such changes better not be made just before the release.

3 files changed, 20 insertions, 3 deletions

diff --git a/source/blender/editors/include/ED_mesh.h b/source/blender/editors/include/ED_mesh.h
index 3d15f349f9b..02c7d52f08d 100644
--- a/source/blender/editors/include/ED_mesh.h
+++ b/source/blender/editors/include/ED_mesh.h
@@ -79,6 +79,7 @@ struct BMVert *EDBM_verts_mirror_get(struct BMEditMesh *em, struct BMVert *v);
 void           EDBM_verts_mirror_cache_clear(struct BMEditMesh *em, struct BMVert *v);
 void           EDBM_verts_mirror_cache_end(struct BMEditMesh *em);
 
+void EDBM_mesh_ensure_valid_dm_hack(struct Scene *scene, struct BMEditMesh *em);
 void EDBM_mesh_normals_update(struct BMEditMesh *em);
 void EDBM_mesh_clear(struct BMEditMesh *em);
 
diff --git a/source/blender/editors/mesh/editmesh_loopcut.c b/source/blender/editors/mesh/editmesh_loopcut.c
index 8b13cc61d3e..c0a36e24015 100644
--- a/source/blender/editors/mesh/editmesh_loopcut.c
+++ b/source/blender/editors/mesh/editmesh_loopcut.c
@@ -373,11 +373,12 @@ static void ringsel_exit(bContext *UNUSED(C), wmOperator *op)
 	op->customdata = NULL;
 }
 
+
 /* called when modal loop selection gets set up... */
 static int ringsel_init(bContext *C, wmOperator *op, int do_cut)
 {
 	RingSelOpData *lcd;
-	
+
 	/* alloc new customdata */
 	lcd = op->customdata = MEM_callocN(sizeof(RingSelOpData), "ringsel Modal Op Data");
 	
@@ -392,7 +393,10 @@ static int ringsel_init(bContext *C, wmOperator *op, int do_cut)
 	initNumInput(&lcd->num);
 	lcd->num.idx_max = 0;
 	lcd->num.flag |= NUM_NO_NEGATIVE | NUM_NO_FRACTION;
-	
+
+	/* XXX, temp, workaround for [#	] */
+	EDBM_mesh_ensure_valid_dm_hack(CTX_data_scene(C), lcd->em);
+
 	em_setup_viewcontext(C, &lcd->vc);
 
 	ED_region_tag_redraw(lcd->ar);
diff --git a/source/blender/editors/mesh/editmesh_utils.c b/source/blender/editors/mesh/editmesh_utils.c
index b844ba0baa2..537d463dfbc 100644
--- a/source/blender/editors/mesh/editmesh_utils.c
+++ b/source/blender/editors/mesh/editmesh_utils.c
@@ -48,6 +48,8 @@
 #include "BKE_report.h"
 #include "BKE_tessmesh.h"
 
+#include "BKE_object.h"  /* XXX. only for EDBM_mesh_ensure_valid_dm_hack() which will be removed */
+
 #include "WM_api.h"
 #include "WM_types.h"
 
@@ -102,7 +104,17 @@ void EDBM_redo_state_free(BMBackup *backup, BMEditMesh *em, int recalctess)
 		BMEdit_RecalcTessellation(em);
 }
 
-
+/* hack to workaround multiple operators being called within the same event loop without an update
+ * see: [#31811] */
+void EDBM_mesh_ensure_valid_dm_hack(Scene *scene, BMEditMesh *em)
+{
+	if ((((ID *)em->ob->data)->flag & LIB_ID_RECALC) ||
+	    (em->ob->recalc & OB_RECALC_DATA))
+	{
+		em->ob->recalc |= OB_RECALC_DATA;  /* since we may not have done selection flushing */
+		BKE_object_handle_update(scene, em->ob);
+	}
+}
 
 void EDBM_mesh_normals_update(BMEditMesh *em)
 {