Tweaks to selection from 3D scene

src/slic3r/GUI/GLCanvas3D.cpp

@@ -2569,8 +2569,7 @@ void GLCanvas3D::on_mouse(wxMouseEvent& evt)
                         m_selection.remove(m_hover_volume_id);
                     else
                     {
-                        bool add_as_single = !already_selected && !ctrl_down;
+                        m_selection.add(m_hover_volume_id, !ctrl_down);
-                        m_selection.add(m_hover_volume_id, add_as_single);
                         m_mouse.drag.move_requires_threshold = !already_selected;
                         if (already_selected)
                             m_mouse.set_move_start_threshold_position_2D_as_invalid();

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -1979,7 +1979,7 @@ void ObjectList::update_selections()
         if (selection.is_single_full_object() && 
             m_objects_model->GetIdByItem(m_objects_model->GetParent(item)) == selection.get_object_idx())
             return; 
-        if (selection.is_single_volume() || selection.is_modifier()) {
+        if (selection.is_single_volume() || selection.is_any_modifier()) {
             const auto gl_vol = selection.get_volume(*selection.get_volume_idxs().begin());
             if (m_objects_model->GetVolumeIdByItem(m_objects_model->GetParent(item)) == gl_vol->volume_idx())
                 return;
@@ -2014,7 +2014,7 @@ void ObjectList::update_selections()
             }
         }
     }
-    else if (selection.is_single_volume() || selection.is_modifier() || selection.is_multiple_volume()) 
+    else if (selection.is_any_volume() || selection.is_any_modifier())
     {
         for (auto idx : selection.get_volume_idxs()) {
             const auto gl_vol = selection.get_volume(idx);

src/slic3r/GUI/Selection.cpp

@@ -109,19 +109,20 @@ void Selection::add(unsigned int volume_idx, bool as_single_selection)
     if (is_wipe_tower() && volume->is_wipe_tower)
         return;
 
-    bool keep_instance_mode = (m_mode == Instance) && !as_single_selection && (is_single_full_instance() || is_multiple_full_instance());
+    bool keep_instance_mode = (m_mode == Instance) && !as_single_selection;
+    bool already_contained = contains_volume(volume_idx);
 
     // resets the current list if needed
-    bool needs_reset = as_single_selection;
+    bool needs_reset = as_single_selection && !already_contained;
     needs_reset |= volume->is_wipe_tower;
     needs_reset |= is_wipe_tower() && !volume->is_wipe_tower;
-    needs_reset |= !keep_instance_mode && !is_modifier() && volume->is_modifier;
+    needs_reset |= as_single_selection && !is_any_modifier() && volume->is_modifier;
-    needs_reset |= is_modifier() && !volume->is_modifier;
+    needs_reset |= is_any_modifier() && !volume->is_modifier;
 
     if (needs_reset)
         clear();
 
-    if (!contains_volume(volume_idx))
+    if (!already_contained || needs_reset)
     {
         if (!keep_instance_mode)
             m_mode = volume->is_modifier ? Volume : Instance;

src/slic3r/GUI/Selection.hpp

@@ -213,7 +213,7 @@ public:
 
     bool is_empty() const { return m_type == Empty; }
     bool is_wipe_tower() const { return m_type == WipeTower; }
-    bool is_modifier() const { return (m_type == SingleModifier) || (m_type == MultipleModifier); }
+    bool is_any_modifier() const { return is_single_modifier() || is_multiple_modifier(); }
     bool is_single_modifier() const { return m_type == SingleModifier; }
     bool is_multiple_modifier() const { return m_type == MultipleModifier; }
     bool is_single_full_instance() const;
@@ -222,6 +222,7 @@ public:
     bool is_multiple_full_object() const { return m_type == MultipleFullObject; }
     bool is_single_volume() const { return m_type == SingleVolume; }
     bool is_multiple_volume() const { return m_type == MultipleVolume; }
+    bool is_any_volume() const { return is_single_volume() || is_multiple_volume(); }
     bool is_mixed() const { return m_type == Mixed; }
     bool is_from_single_instance() const { return get_instance_idx() != -1; }
     bool is_from_single_object() const;