From 0c84a0b696d7d3bd35cd0d58f90a98a96f153cc3 Mon Sep 17 00:00:00 2001
From: Lukas Matena <lukasmatena@seznam.cz>
Date: Thu, 30 Apr 2020 15:12:59 +0200
Subject: [PATCH] Fixed SLA supports gizmo undo/redo stack broken by 4f43c6d
 even before 2.2.0 release

---
 src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.cpp | 7 +++----
 src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.hpp | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.cpp b/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.cpp
index 496568d51..261738d44 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.cpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.cpp
@@ -66,11 +66,10 @@ void GLGizmoSlaSupports::set_sla_support_data(ModelObject* model_object, const S
 
     ModelObject* mo = m_c->selection_info()->model_object();
 
-    if (mo != m_old_mo) {
+    if (mo && mo->id() != m_old_mo_id) {
         disable_editing_mode();
-        if (mo)
-            reload_cache();
-        m_old_mo = mo;
+        reload_cache();
+        m_old_mo_id = mo->id();
     }
 
     // If we triggered autogeneration before, check backend and fetch results if they are there
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.hpp b/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.hpp
index 917d22a98..b6cad8f9a 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.hpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.hpp
@@ -83,7 +83,7 @@ private:
     float m_density_stash = 0.f;                // and again
     mutable std::vector<CacheEntry> m_editing_cache; // a support point and whether it is currently selected
     std::vector<sla::SupportPoint> m_normal_cache; // to restore after discarding changes or undo/redo
-    const ModelObject* m_old_mo = nullptr;
+    ObjectID m_old_mo_id;
 
     // This map holds all translated description texts, so they can be easily referenced during layout calculations
     // etc. When language changes, GUI is recreated and this class constructed again, so the change takes effect.