[cairo] basic question?

[Carl Worth]

Excerpts from Charles سمير Doutriaux's message of Tue Aug 18 14:09:43 -0700 2009:
> On Aug 18, 2009, at 1:54 PM, David Björkevik wrote:
> > Charles سمير Doutriaux wrote:
> >> For speed reason I'm thinking it would be better to draw "in memory"
> >> on a cairo_image surface and then whenever I need to update copy the
> >> image back to my X11 window.
> >
> > This is not correct. When drawing through X, cairo uses XRENDER  
> > which is
> > hardware accelerated (if your X driver supports it).
> 
> Actually, speed is not the only issue, the way our software is  
> designed there's a LOT of polygons to fill and it is more pleasant to  
> the user to see the image pop up finished instead of looking at it  
> being drawn.

OK, Charles, but you're the one who said "for speed reasons". :-)

As for not making the user look at the thing being drawn, you can also
do that with cairo-xlib by simply creating a Pixmap, directing cairo
at that, and finally copying the Pixmap to the Window when complete.

Of course, using a cairo_image_surface_t should work identically too.

The only result *should* be that the image surface is strictly slower
than the xlib surface, (though sometimes driver bugs do get in the way
and make xlib drawing slower than image).

-Carl
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