ui: Enable/Disable undo/redo contextmenu

src/lib_gui/qt/utility/QtContextMenu.cpp

@@ -56,6 +56,16 @@ void QtContextMenu::addAction(QAction* action)
 	m_menu.addAction(action);
 }
 
+void QtContextMenu::enableUndo(bool enabled)
+{
+	s_undoAction->setEnabled(enabled);
+}
+
+void QtContextMenu::enableRedo(bool enabled)
+{
+	s_redoAction->setEnabled(enabled);
+}
+
 void QtContextMenu::addUndoActions()
 {
 	addAction(s_undoAction);

src/lib_gui/qt/utility/QtContextMenu.h

@@ -25,6 +25,9 @@ public:
 
 	void show();
 
+	static void enableUndo(bool enabled);
+	static void enableRedo(bool enabled);
+
 private slots:
 	void undoActionTriggered();
 	void redoActionTriggered();