call render in main thread by function callAfter(hint by @Vojtech)

src/slic3r/GUI/Gizmos/GLGizmoBase.cpp

@@ -157,9 +157,8 @@ void GLGizmoBase::update(const UpdateData& data)
 
 bool GLGizmoBase::update_items_state()
 {
-    std::lock_guard<std::mutex> g(m_dirty_access); 
     bool res = m_dirty;
-    m_dirty = false;
+    m_dirty  = false;
     return res;
 };
 
@@ -218,8 +217,7 @@ std::string GLGizmoBase::format(float value, unsigned int decimals) const
     return Slic3r::string_printf("%.*f", decimals, value);
 }
 
-void GLGizmoBase::set_dirty() { 
-    std::lock_guard<std::mutex> g(m_dirty_access); 
+void GLGizmoBase::set_dirty() {
     m_dirty = true;
 }
 

src/slic3r/GUI/Gizmos/GLGizmoBase.hpp

@@ -1,7 +1,6 @@
 #ifndef slic3r_GLGizmoBase_hpp_
 #define slic3r_GLGizmoBase_hpp_
 
-#include <mutex>
 #include "libslic3r/Point.hpp"
 
 #include "slic3r/GUI/I18N.hpp"
@@ -154,6 +153,8 @@ public:
     bool is_dragging() const { return m_dragging; }
 
     void update(const UpdateData& data);
+
+    // returns True when Gizmo changed its state
     bool update_items_state();
 
     void render() { m_tooltip.clear(); on_render(); }
@@ -190,10 +191,11 @@ protected:
 
     std::string format(float value, unsigned int decimals) const;
 
+    // Mark gizmo as dirty to Re-Render when idle()
     void set_dirty();
-
 private:
-    std::mutex m_dirty_access;
+    // Flag for dirty visible state of Gizmo
+    // When True then need new rendering
     bool m_dirty;
 };
 

src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp

@@ -253,7 +253,7 @@ void GLGizmoSimplify::process()
     plater->clear_before_change_mesh(m_obj_index);
     m_progress = 0;
     if (m_worker.joinable()) m_worker.join();
-    m_worker = std::thread([&]() {
+    m_worker = std::thread([this]() {
         // store original triangles        
         uint32_t triangle_count = (m_configuration.use_count) ? m_configuration.wanted_count : 0;
         float    max_error      = (m_configuration.use_error) ? 
@@ -264,10 +264,16 @@ void GLGizmoSimplify::process()
                 throw SimplifyCanceledException();
             }
         };
-        std::function<void(int)> statusfn = [&](int percent) { 
+
+        std::function<void(int)> statusfn = [this](int percent) {
             m_progress = percent;
-            set_dirty();
-            m_parent.schedule_extra_frame(0);
+
+            // check max 4fps
+            static int64_t last = 0;
+            int64_t now = m_parent.timestamp_now();
+            if ((now - last) < 250) return;
+
+            request_rerender();
         };
 
         indexed_triangle_set collapsed;
@@ -290,9 +296,8 @@ void GLGizmoSimplify::process()
             // set state out of main thread
             m_state = State::settings; 
         }
-        // need to render last status fn to change bar graph to buttons
-        set_dirty();
-        m_parent.schedule_extra_frame(0);
+        // need to render last status fn to change bar graph to buttons        
+        request_rerender();
     });
 }
 
@@ -335,6 +340,9 @@ void GLGizmoSimplify::on_set_state()
 
         // invalidate selected model
         m_volume = nullptr;
+    } else if (GLGizmoBase::m_state == GLGizmoBase::On) {
+        // when open by hyperlink it needs to show up
+        request_rerender();
     }
 }
 
@@ -360,4 +368,11 @@ void GLGizmoSimplify::create_gui_cfg() {
     m_gui_cfg = cfg;
 }
 
+void GLGizmoSimplify::request_rerender() {
+    wxGetApp().plater()->CallAfter([this]() {
+        set_dirty();
+        m_parent.schedule_extra_frame(0);
+    });
+}
+
 } // namespace Slic3r::GUI

src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp

@@ -35,6 +35,7 @@ private:
     void process();
     void set_its(indexed_triangle_set &its);
     void create_gui_cfg();
+    void request_rerender();
 
     bool m_is_valid_result; // differ what to do in apply
     volatile int m_progress; // percent of done work