qt4agg: fix blit bug; closes #506

efiring · efiring · commit e315e90532a5 · 2011-10-05T14:20:02.000-10:00
A simple Cursor test script was causing infinite recursion.
The solution here involves using separate attributes for the
replot flag (meaning an Agg draw is needed) and the blitbox.
This clarifies the logic and removes the need to override
the inherited copy_from_bbox method.
diff --git a/lib/matplotlib/backends/backend_qt4agg.py b/lib/matplotlib/backends/backend_qt4agg.py
@@ -58,6 +58,7 @@ def __init__( self, figure ):
         FigureCanvasAgg.__init__( self, figure )
         self.drawRect = False
         self.rect = []
+        self.blitbox = None
         self.replot = True
         self.setAttribute(QtCore.Qt.WA_OpaquePaintEvent)
 
@@ -77,11 +78,11 @@ def paintEvent( self, e ):
         if DEBUG: print 'FigureCanvasQtAgg.paintEvent: ', self, \
            self.get_width_height()
 
-        # only replot data when needed
-        if type(self.replot) is bool: # might be a bbox for blitting
-            if self.replot:
-                FigureCanvasAgg.draw(self)
+        if self.replot:
+            FigureCanvasAgg.draw(self)
+            self.replot = False
 
+        if self.blitbox is None:
             # matplotlib is in rgba byte order.  QImage wants to put the bytes
             # into argb format and is in a 4 byte unsigned int.  Little endian
             # system is LSB first and expects the bytes in reverse order
@@ -91,7 +92,7 @@ def paintEvent( self, e ):
             else:
                 stringBuffer = self.renderer._renderer.tostring_argb()
 
-            qImage = QtGui.QImage(stringBuffer, self.renderer.width, 
+            qImage = QtGui.QImage(stringBuffer, self.renderer.width,
                                   self.renderer.height,
                                   QtGui.QImage.Format_ARGB32)
             p = QtGui.QPainter(self)
@@ -101,23 +102,21 @@ def paintEvent( self, e ):
             if self.drawRect:
                 p.setPen( QtGui.QPen( QtCore.Qt.black, 1, QtCore.Qt.DotLine ) )
                 p.drawRect( self.rect[0], self.rect[1], self.rect[2], self.rect[3] )
-
             p.end()
-        # we are blitting here
         else:
-            bbox = self.replot
+            bbox = self.blitbox
             l, b, r, t = bbox.extents
             w = int(r) - int(l)
             h = int(t) - int(b)
             t = int(b) + h
-            reg = FigureCanvasAgg.copy_from_bbox(self, bbox)
+            reg = self.copy_from_bbox(bbox)
             stringBuffer = reg.to_string_argb()
             qImage = QtGui.QImage(stringBuffer, w, h, QtGui.QImage.Format_ARGB32)
             pixmap = QtGui.QPixmap.fromImage(qImage)
             p = QtGui.QPainter( self )
             p.drawPixmap(QtCore.QPoint(l, self.renderer.height-t), pixmap)
             p.end()
-        self.replot = False
+            self.blitbox = None
         self.drawRect = False
 
     def draw( self ):
@@ -133,22 +132,11 @@ def blit(self, bbox=None):
         """
         Blit the region in bbox
         """
-
-        self.replot = bbox
+        self.blitbox = bbox
         l, b, w, h = bbox.bounds
         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()
