Painting gizmos: show painted triangles inside modifier meshes

src/slic3r/GUI/GLCanvas3D.cpp

@@ -5461,6 +5461,20 @@ void GLCanvas3D::_render_objects() const
             });
         }
 
+        // In case a painting gizmo is open, it should render the painted triangles
+        // before transparent objects are rendered. Otherwise they would not be
+        // visible when inside modifier meshes etc.
+        {
+            const GLGizmosManager& gm = get_gizmos_manager();
+            GLGizmosManager::EType type = gm.get_current_type();
+            if (type == GLGizmosManager::FdmSupports
+             || type == GLGizmosManager::Seam) {
+                shader->stop_using();
+                gm.render_painter_gizmo();
+                shader->start_using();
+            }
+        }
+
         m_volumes.render(GLVolumeCollection::Transparent, false, wxGetApp().plater()->get_camera().get_view_matrix());
         shader->stop_using();
     }

src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp

@@ -56,7 +56,7 @@ bool GLGizmoFdmSupports::on_init()
 
 
 
-void GLGizmoFdmSupports::on_render() const
+void GLGizmoFdmSupports::render_painter_gizmo() const
 {
     const Selection& selection = m_parent.get_selection();
 

src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.hpp

@@ -13,14 +13,14 @@ public:
     GLGizmoFdmSupports(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id)
         : GLGizmoPainterBase(parent, icon_filename, sprite_id) {}
 
+    void render_painter_gizmo() const override;
+
 protected:
     void on_render_input_window(float x, float y, float bottom_limit) override;
     std::string on_get_name() const override;
 
 private:
     bool on_init() override;
-    void on_render() const override;
-    void on_render_for_picking() const override {}
 
     void update_model_object() const override;
     void update_from_model_object() override;

src/slic3r/GUI/Gizmos/GLGizmoPainterBase.hpp

@@ -59,6 +59,8 @@ class GLGizmoPainterBase : public GLGizmoBase
 private:
     ObjectID m_old_mo_id;
     size_t m_old_volumes_size = 0;
+    virtual void on_render() const {}
+    virtual void on_render_for_picking() const {}
 
 public:
     GLGizmoPainterBase(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id);
@@ -66,6 +68,12 @@ public:
     void set_painter_gizmo_data(const Selection& selection);
     bool gizmo_event(SLAGizmoEventType action, const Vec2d& mouse_position, bool shift_down, bool alt_down, bool control_down);
 
+    // Following function renders the triangles and cursor. Having this separated
+    // from usual on_render method allows to render them before transparent objects,
+    // so they can be seen inside them. The usual on_render is called after all
+    // volumes (including transparent ones) are rendered.
+    virtual void render_painter_gizmo() const = 0;
+
 protected:
     void render_triangles(const Selection& selection) const;
     void render_cursor() const;

src/slic3r/GUI/Gizmos/GLGizmoSeam.cpp

@@ -46,7 +46,7 @@ std::string GLGizmoSeam::on_get_name() const
 
 
 
-void GLGizmoSeam::on_render() const
+void GLGizmoSeam::render_painter_gizmo() const
 {
     const Selection& selection = m_parent.get_selection();
 

src/slic3r/GUI/Gizmos/GLGizmoSeam.hpp

@@ -13,6 +13,8 @@ public:
     GLGizmoSeam(GLCanvas3D& parent, const std::string& icon_filename, unsigned int sprite_id)
         : GLGizmoPainterBase(parent, icon_filename, sprite_id) {}
 
+    void render_painter_gizmo() const override;
+
 protected:
     void on_render_input_window(float x, float y, float bottom_limit) override;
     std::string on_get_name() const override;
@@ -20,8 +22,6 @@ protected:
 
 private:
     bool on_init() override;
-    void on_render() const override;
-    void on_render_for_picking() const override {}
 
     void update_model_object() const override;
     void update_from_model_object() override;

src/slic3r/GUI/Gizmos/GLGizmosManager.cpp

@@ -437,6 +437,19 @@ void GLGizmosManager::render_current_gizmo() const
     m_gizmos[m_current]->render();
 }
 
+void GLGizmosManager::render_painter_gizmo() const
+{
+    // This function shall only be called when current gizmo is
+    // derived from GLGizmoPainterBase.
+
+    if (!m_enabled || m_current == Undefined)
+        return;
+
+    auto* gizmo = dynamic_cast<GLGizmoPainterBase*>(get_current());
+    assert(gizmo); // check the precondition
+    gizmo->render_painter_gizmo();
+}
+
 void GLGizmosManager::render_current_gizmo_for_picking_pass() const
 {
     if (! m_enabled || m_current == Undefined)

src/slic3r/GUI/Gizmos/GLGizmosManager.hpp

@@ -212,6 +212,7 @@ public:
 
     void render_current_gizmo() const;
     void render_current_gizmo_for_picking_pass() const;
+    void render_painter_gizmo() const;
 
     void render_overlay() const;