backend_qt4agg: eliminate duplicate call to FigureCanvasAgg.draw()

efiring · efiring · commit 6938b0025583 · 2011-01-17T07:13:37.000Z
The basic problem is that the most efficient way to eliminate the
duplication appears to be to do the Agg drawing in the paintEvent,
not in draw(); but then a draw() followed by copy_from_bbox may
result in a copy being made before the Agg draw has occurred.
The solution here is to do that drawing inside copy_from_bbox
when necessary.

Side note: it seems that by using the update() method, the
qt4agg draw() is acting more like draw_idle() than like the draw()
methods in the other interactive backends.


svn path=/trunk/matplotlib/; revision=8922
diff --git a/lib/matplotlib/backends/backend_qt4agg.py b/lib/matplotlib/backends/backend_qt4agg.py
@@ -110,7 +110,7 @@ def paintEvent( self, e ):
             w = int(r) - int(l)
             h = int(t) - int(b)
             t = int(b) + h
-            reg = self.copy_from_bbox(bbox)
+            reg = FigureCanvasAgg.copy_from_bbox(self, bbox)
             stringBuffer = reg.to_string_argb()
             qImage = QtGui.QImage(stringBuffer, w, h, QtGui.QImage.Format_ARGB32)
             pixmap = QtGui.QPixmap.fromImage(qImage)
@@ -127,7 +127,6 @@ def draw( self ):
 
         if DEBUG: print "FigureCanvasQtAgg.draw", self
         self.replot = True
-        FigureCanvasAgg.draw(self)
         self.update()
 
     def blit(self, bbox=None):
@@ -140,6 +139,16 @@ def blit(self, bbox=None):
         t = b + h
         self.repaint(l, self.renderer.height-t, w, h)
 
+    def copy_from_bbox(self, *args):
+        """
+        If a draw() has been called but the update() has not
+        occurred, draw into the agg canvas before copying.
+        """
+        if self.replot:
+            FigureCanvasAgg.draw(self)
+            self.replot = False
+        return FigureCanvasAgg.copy_from_bbox(self, *args)
+
     def print_figure(self, *args, **kwargs):
         FigureCanvasAgg.print_figure(self, *args, **kwargs)
         self.draw()
