Network: Add undo command for node move.

src/View/Network/GraphWidget.py

@@ -669,14 +669,15 @@ class GraphWidget(QGraphicsView):
         if self._state == "move":
             self._selected_new_edge_src_node = None
 
-            self.mouse_origin_x = pos.x()
-            self.mouse_origin_y = pos.y()
-
             items = self.items(event.pos())
             if items and type(items[0]) == EdgeItem:
                 edge = items[0]
                 if edge:
                     self.set_current_edge(edge)
+            elif items and type(items[0]) == NodeItem:
+                self._mouse_origin_x = pos.x()
+                self._mouse_origin_y = pos.y()
+                self._current_moved_node = items[0]
 
         # Add nodes and edges
         elif self._state == "add":
@@ -712,6 +713,17 @@ class GraphWidget(QGraphicsView):
     def mouseReleaseEvent(self, event):
         self.clicked = False
 
+        if self._state == "move":
+            pos = self.mapToScene(event.pos())
+            self._undo.push(
+                SetNodePosCommand(
+                    self._current_moved_node,
+                    (pos.x(), pos.y()),
+                    (self._mouse_origin_x,
+                     self._mouse_origin_y)
+                )
+            )
+
         self.update()
         super(GraphWidget, self).mouseReleaseEvent(event)