Reduce flicker in svg demos

demo/SVGImage_Bitmap.py

@@ -21,6 +21,8 @@ class SVGBitmapDisplay(wx.Panel):
         sbox = wx.StaticBoxSizer(wx.VERTICAL, self, label)
         sbox.Add(self.statbmp)
         self.SetSizer(sbox)
+        if not self.IsDoubleBuffered():
+            self.SetDoubleBuffered(True)  # Reduce flicker on size event.
 
 
     def UpdateSVG(self, svg_filename):

demo/SVGImage_Render.py

@@ -33,7 +33,7 @@ class SVGRenderPanel(wx.Panel):
 
 
     def OnPaint(self, event):
-        dc = wx.PaintDC(self)
+        dc = wx.BufferedPaintDC(self)
         dc.Clear()
 
         iw, ih = (self._img.width, self._img.height) if self._img else (100,100)