Addition of a "lock" property in the groups API.

Polyhedron/demo/Polyhedron/Scene.cpp

@@ -127,12 +127,14 @@ Scene::replaceItem(Scene::Item_id index, CGAL::Three::Scene_item* item, bool emi
 Scene::Item_id
 Scene::erase(Scene::Item_id index)
 {
+  CGAL::Three::Scene_item* item = m_entries[index];
+  if(item->parentGroup()
+     && item->parentGroup()->isChildLocked(item))
+    return -1;
     clear();
     index_map.clear();
     if(index < 0 || index >= m_entries.size())
         return -1;
-
-    CGAL::Three::Scene_item* item = m_entries[index];
     CGAL::Three::Scene_group_item* group =
             qobject_cast<CGAL::Three::Scene_group_item*>(item);
   if(group)
@@ -173,6 +175,9 @@ Scene::erase(QList<int> indices)
 
     max_index = (std::max)(max_index, index);
     CGAL::Three::Scene_item* item = m_entries[index];
+    if(item->parentGroup()
+       && item->parentGroup()->isChildLocked(item))
+      continue;
     if(!to_be_removed.contains(item))
       to_be_removed.push_back(item);
   }
@@ -747,7 +752,9 @@ bool Scene::dropMimeData(const QMimeData * /*data*/,
   Q_FOREACH(int i, selected_items_list)
   {
     if(!groups_children.contains(i))
+    {
       items << item(i);
+    }
   }
   //Gets the group at the drop position
   CGAL::Three::Scene_group_item* group =
@@ -1108,7 +1115,11 @@ void Scene::changeGroup(Scene_item *item, CGAL::Three::Scene_group_item *target_
 {
     //remove item from the containing group if any
     if(item->parentGroup())
-        item->parentGroup()->removeChild(item);
+    {
+      if(item->parentGroup()->isChildLocked(item))
+        return;
+      item->parentGroup()->removeChild(item);
+    }
     //add the item to the target group
     target_group->addChild(item);
     item->moveToGroup(target_group);

Polyhedron/demo/Polyhedron/Scene_c3t3_item.cpp

@@ -1165,10 +1165,12 @@ void Scene_c3t3_item::show_spheres(bool b)
     connect(spheres, SIGNAL(destroyed()), this, SLOT(reset_spheres()));
     last_known_scene->addItem(spheres);
     last_known_scene->changeGroup(spheres, this);
+    lockChild(spheres);
     compute_spheres();
   }
   else if (!b && spheres!=NULL)
   {
+    unlockChild(spheres);
     last_known_scene->erase(last_known_scene->item_id(spheres));
   }
   Q_EMIT redraw();

Polyhedron/demo/Polyhedron/Scene_group_item.cpp

@@ -213,3 +213,23 @@ void Scene_group_item::draw_splats(CGAL::Three::Viewer_interface* viewer) const
       child->draw_splats(viewer);
   }
 }
+
+void Scene_group_item::lockChild(Scene_item *child)
+{
+  if(!children.contains(child))
+    return;
+  child->setProperty("lock", true);
+}
+void Scene_group_item::unlockChild(Scene_item *child)
+{
+  if(!children.contains(child))
+    return;
+  child->setProperty("lock", false);
+}
+bool Scene_group_item::isChildLocked(Scene_item *child)
+{
+  if(!children.contains(child)
+     || (!child->property("lock").toBool()) )
+    return false;
+  return true;
+}

Three/include/CGAL/Three/Scene_group_item.h

@@ -46,6 +46,22 @@ public :
     bool isFinite() const;
     //!Returns true to avoid disturbing the BBox of the scene.
     bool isEmpty() const ;
+    /*!
+     * \brief Locks a child
+     * A locked child cannot be moved out of the group nor can it be deleted.
+     */
+    void lockChild(CGAL::Three::Scene_item*);
+    /*!
+     * \brief Unlocks a child
+     * @see lockChild()
+     */
+    void unlockChild(CGAL::Three::Scene_item*);
+    /*!
+     * \brief Tells if a child is locked.
+     * \return true if the child is locked.
+     * @see lockChild()
+     */
+    bool isChildLocked(CGAL::Three::Scene_item*);
     //!Returns if the group_item is currently expanded or collapsed in the view.
     //! True means expanded, false means collapsed.
     //! @see setExpanded.
@@ -122,6 +138,8 @@ public :
     //!@see getChildren @see addChild
     void removeChild( Scene_item* item)
     {
+     if(isChildLocked(item))
+      return;
       update_group_number(item,0);
       children.removeOne(item);
     }