[racket] Slideshow's current-font-size 1-255

I've changed the limit to 1024, which brings it back in sync with
`font%'.

The 256 limit was an old platform-imposed constraint. Also, some other
platforms could immediately exhaust memory when given a large enough
font size.

The actually platform limit now is probably about 1000 times larger
(constrained by a C datatype) than 1024. I'm not yet sure that there
are no resource issues with large font sizes, though, so that's why the
limit isn't higher. I'll continue investigating.

At Fri, 16 Mar 2012 01:46:03 -0300, Rodolfo Carvalho wrote:
> Hello,
> 
> I was trying to make a slide with a large symbol on it.
> 
> #lang slideshow
> (slide
>  (parameterize ([current-font-size 280])
>    (t "\u2623")))
> 
> That gives a contract violation, saying that current-font-size isn't
> (between/c 1 255).
> 
> Why can't we have font sizes larger than 255?
> 
> 
> BTW, I am able to get a large pict by scaling (though, then, with rough
> edges):
> 
> (slide
>  (scale/improve-new-text (t "\u2623") 20))
> 
> 
> []'s
> 
> Rodolfo Carvalho
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