Re: the right way to draw in a drawingarea

[Paul Davis <pjdavis engineering uiowa edu>]

Foster, Gareth wrote:

> > the display flickers, even when drawing a simple square.
> >
> >    
>
> Doesn't this often mean you need to be double buffering?
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This is a point I am completely unsure about.  I haven't the foggiest on 
Gtk internals and the ramifications of a simple call such as 
draw_rectangle.  I've used double buffering in both OpenGL and Java.  
I've just never really seen any real reference to it in gtk.  Now that 
I've had a couple beers, I seem to rememeber some reference to getting 
an offscreen graphics context, drawing to that, and then switching the 
main gc with it back and forth.  But I could be completely making that 
up. ( the beer )

Double buffering isn't really that hard of a concept.  I'm just not sure 
of if its needed.  Because its more than possible that gtk has its own 
buffering scheme burried somewhere.  I've actually written a couple 
programs to animate image data using Gtkmm.  I've never had a problem 
with flickering that wasn't because I was doing something silly like 
clearing and then redrawing.  So the answer is I dunno.  Its possible.  
If I get time I'll write a test program to try and play with the idea.

And if I had thought to take a moment to google something as silly as 
gtkmm double buffering, I would have noticed that the gtkmm docs specify 
that widgets are double buffered by default.  In which case, no double 
buffering will not solve this problem cause its already being done.  
Which goes to show that yes, I was making up the graphics context 
thing.  Must be something from java I was thinking of.
http://www.gtkmm.org/docs/gtkmm-2.4/docs/reference/html/classGtk_1_1Widget.html#a175

In other news, Unleashed wasn't half bad if anyone cares.

Cheers,
Paul