From 12bde317f4c94d48a154c8815ad910ccdd73be74 Mon Sep 17 00:00:00 2001
From: Hans Goudey <h.goudey@me.com>
Date: Fri, 24 Jun 2022 16:39:58 -0500
Subject: Fix T98949: Deleting vertex group in geometry nodes affects others

The vertex group indices stored in the weights need to be accounted for
when the vertex group list on the mesh changes.
---
 source/blender/blenkernel/intern/geometry_component_mesh.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/source/blender/blenkernel/intern/geometry_component_mesh.cc b/source/blender/blenkernel/intern/geometry_component_mesh.cc
index 88ea1af8a8d..9e64acf218b 100644
--- a/source/blender/blenkernel/intern/geometry_component_mesh.cc
+++ b/source/blender/blenkernel/intern/geometry_component_mesh.cc
@@ -1092,6 +1092,11 @@ class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
     for (MDeformVert &dvert : MutableSpan(mesh->dvert, mesh->totvert)) {
       MDeformWeight *weight = BKE_defvert_find_index(&dvert, index);
       BKE_defvert_remove_group(&dvert, weight);
+      for (MDeformWeight &weight : MutableSpan(dvert.dw, dvert.totweight)) {
+        if (weight.def_nr > index) {
+          weight.def_nr--;
+        }
+      }
     }
     return true;
   }
-- 
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