From 4d0dbab5b1bfcef76d14c43f4659792841be12c0 Mon Sep 17 00:00:00 2001
From: Alexander Gavrilov <angavrilov@gmail.com>
Date: Wed, 8 Feb 2023 14:27:43 +0200
Subject: [PATCH] Mesh Edit: implement X symmetry in the Propagate To Shapes
 operator.

Since the operator affects shape keys rather than current mesh
coordinates, this only symmetrizes the selection.

Pull Request #105421
---
 source/blender/editors/mesh/editmesh_tools.cc | 23 ++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/source/blender/editors/mesh/editmesh_tools.cc b/source/blender/editors/mesh/editmesh_tools.cc
index e50b9987d2f..1d286b5622f 100644
--- a/source/blender/editors/mesh/editmesh_tools.cc
+++ b/source/blender/editors/mesh/editmesh_tools.cc
@@ -3703,7 +3703,7 @@ void MESH_OT_remove_doubles(wmOperatorType *ot)
  * \{ */
 
 /* BMESH_TODO this should be properly encapsulated in a bmop.  but later. */
-static bool shape_propagate(BMEditMesh *em)
+static bool shape_propagate(BMEditMesh *em, bool use_symmetry)
 {
   BMIter iter;
   BMVert *eve = nullptr;
@@ -3716,7 +3716,12 @@ static bool shape_propagate(BMEditMesh *em)
 
   BM_ITER_MESH (eve, &iter, em->bm, BM_VERTS_OF_MESH) {
     if (!BM_elem_flag_test(eve, BM_ELEM_SELECT) || BM_elem_flag_test(eve, BM_ELEM_HIDDEN)) {
-      continue;
+      BMVert *mirr = use_symmetry ? EDBM_verts_mirror_get(em, eve) : NULL;
+
+      if (!mirr || !BM_elem_flag_test(mirr, BM_ELEM_SELECT) ||
+          BM_elem_flag_test(mirr, BM_ELEM_HIDDEN)) {
+        continue;
+      }
     }
 
     for (int i = 0; i < totshape; i++) {
@@ -3748,10 +3753,22 @@ static int edbm_shape_propagate_to_all_exec(bContext *C, wmOperator *op)
     }
     tot_selected_verts_objects++;
 
-    if (shape_propagate(em)) {
+    const bool use_symmetry = (me->symmetry & ME_SYMMETRY_X) != 0;
+
+    if (use_symmetry) {
+      const bool use_topology = (me->editflag & ME_EDIT_MIRROR_TOPO) != 0;
+
+      EDBM_verts_mirror_cache_begin(em, 0, false, true, false, use_topology);
+    }
+
+    if (shape_propagate(em, use_symmetry)) {
       tot_shapekeys++;
     }
 
+    if (use_symmetry) {
+      EDBM_verts_mirror_cache_end(em);
+    }
+
     EDBMUpdate_Params params{};
     params.calc_looptri = false;
     params.calc_normals = false;