Scenario: Graph: Fix mouse button event.

src/View/Scenarios/GraphWidget.py

@@ -357,8 +357,10 @@ class GraphWidget(QGraphicsView):
         if len(selectable_items) == 0:
             if event.buttons() & Qt.LeftButton:
                 old_p = self.mapToScene(
-                    float(self.m_origin_x),
-                    float(self.m_origin_y)
+                    QPoint(
+                        int(self.m_origin_x),
+                        int(self.m_origin_y)
+                    )
                 )
                 new_p = self.mapToScene(event.pos())
                 translation = new_p - old_p