Fix visibility icon for link elements

The visibility of link elements must be set with setElementVisible.
This will first try to use that API otherwise it falls back to setting
the Visibility property.

src/Gui/Tree.cpp

@@ -1622,12 +1622,25 @@ void TreeWidget::mousePressEvent(QMouseEvent* event)
 
             // If the visibility icon was clicked, toggle the DocumentObject visibility
             if (iconRect.contains(mousePos)) {
-                auto vp = objitem->object();
-                if (vp->isShow()) {
-                    vp->hide();
-                } else {
-                    vp->show();
+                auto obj = objitem->object()->getObject();
+                char const* objname = obj->getNameInDocument();
+
+                App::DocumentObject* parent = nullptr;
+                std::ostringstream subName;
+                objitem->getSubName(subName, parent);
+
+                // Try the ElementVisible API, if that is not supported toggle the Visibility property
+                int visible = -1;
+                if (parent) {
+                    visible = parent->isElementVisible(objname);
                 }
+                if (parent && visible >= 0) {
+                    parent->setElementVisible(objname, !visible);
+                } else {
+                    visible = obj->Visibility.getValue();
+                    obj->Visibility.setValue(!visible);
+                }
+
                 event->setAccepted(true);
                 return;
             }