(mgp-users 00123) Re: embarassingly slow tfont handling...

[Luigi Rizzo <luigi@labinfo.iet.unipi.it>]

> >i think we have a small performance problem here... it is most
> >evident when i run mgp with truetype fonts and a not-solid background
> >(e.g. an image):
> >    rendering the slides is very slow!
> 
> 	This is because we do anti-aliasing with freetype, and it is not
> 	trivial to draw anti-aliased text on non-solid background.
> 	(you will need to compute the mixed color, basically)

this still does not explain why as the page is displayed again and
again it takes longer and longer. I am talking about going from 300ms
in the first run, 700ms in the second run, and up to 4-5 seconds and
more then i got bored. The initial 300ms could still be acceptable, is
the 10-15fold increase which is not.

I note, in tfont, a section with a comment
	/* XXX: need optimization */ 

where you copy images one pixel at a time -- there, using XPutImage
should probably be more efficient. But it is not this that is
responsible of the time increase. I really have no idea where is the
problem, also because i dont see the memory occupation grow.

btw the student here who did the windows port also does antialiasing
with windows fonts (perhaps using fewer levels than with ttf).

	luigi
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  Luigi RIZZO                      .
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