canvas/nodeitem: Keep track of the text, avoid unnecessary updates

Author: ales-erjavec

Orange/canvas/canvas/items/nodeitem.py

@@ -691,6 +691,7 @@ def __init__(self, *args, **kwargs):
         super(NameTextItem, self).__init__(*args, **kwargs)
         self.__selected = False
         self.__palette = None
+        self.__content = ""
 
     def paint(self, painter, option, widget=None):
         if self.__selected:
@@ -753,6 +754,11 @@ def __updateDefaultTextColor(self):
             role = QPalette.WindowText
         self.setDefaultTextColor(self.palette().color(role))
 
+    def setHtml(self, contents):
+        if contents != self.__content:
+            self.__content = contents
+            super().setHtml(contents)
+
 
 class NodeItem(QGraphicsObject):
     """