[wxPython-users] Re: Not quite understanding buffered DCs

[Robin Dunn]

Jeffrey Barish wrote:
> Robin Dunn wrote:

>> It is all for convenience.  That one line in the example replaces about 
>> 4 lines it would take to do it without a wx.BufferedPaintDC.  In fact, 
>> all of the buffered dc classes are entirely for convenience.  You can do 
>> everything they do yourself with just a bitmap, a MemoryDC and a 
>> ClientDC or PaintDC.
> 
> Sure, in general it takes all those elements.  But in this case, isn't it
> true that we don't need the MemoryDC?  The image that we want to draw is
> already whole in self.bitmap, so we should be able to blit it to the
> PaintDC without having to worry about flicker:
> 
> dc = wx.PaintDC()
> w, h = self.buffer.GetSize()
> dc.Blit(0, 0, w, h, self.buffer, 0, 0)

No, the 5th parameter of Blit is a DC, not a bitmap.  You could do it 
with dc.DrawBitmap instead of Blit, but that just creates a MemoryDC 
internally on most platforms anyway.

> Also, is it true that the additional overhead associated with
> creating the buffered device context (that is, the overhead associated with
> creating the MemoryDC) is small? 

Yes.

-- 
Robin Dunn
Software Craftsman
http://wxPython.org  Java give you jitters?  Relax with wxPython!