Add recursive submenu support for node library.

pyqtgraph/flowchart/Flowchart.py

@@ -823,16 +823,20 @@ class FlowchartWidget(dockarea.DockArea):
         self.buildMenu()
         
     def buildMenu(self, pos=None):
+        def buildSubMenu(node, rootMenu, subMenus, pos=None):
+            for section, node in node.items():
+                menu = QtGui.QMenu(section)
+                rootMenu.addMenu(menu)
+                if isinstance(node, OrderedDict): 
+                    buildSubMenu(node, menu, subMenus, pos=pos)
+                    subMenus.append(menu)
+                else:
+                    act = rootMenu.addAction(section)
+                    act.nodeType = section
+                    act.pos = pos
         self.nodeMenu = QtGui.QMenu()
-        self.subMenus = []
-        for section, nodes in self.chart.library.getNodeTree().items():
-            menu = QtGui.QMenu(section)
-            self.nodeMenu.addMenu(menu)
-            for name in nodes:
-                act = menu.addAction(name)
-                act.nodeType = name
-                act.pos = pos
-            self.subMenus.append(menu)
+        self.subMenus = []       
+        buildSubMenu(library.getNodeTree(), self.nodeMenu, self.subMenus, pos=pos)
         self.nodeMenu.triggered.connect(self.nodeMenuTriggered)
         return self.nodeMenu