Re: gd.trm png_state.default_font

[Ethan M. <merritt@u.washington.edu>]

On Friday 30 October 2009 05:57:02 Tait wrote:
> 
> Here's a transcript from a recent CVS:
> 
> 	Terminal type set to 'windows'
> 	gnuplot> set term png
> 	Terminal type set to 'png'
> 	Options are 'nocrop font arial 12 size 640,480 '
> 	gnuplot> set term windows
> 	Terminal type set to 'windows'
> 	Options are 'color noenhanced'
> 	gnuplot> set term png
> 	Terminal type set to 'png'
> 	gd.trm: caught initialization error
> 	Options are 'nocrop font arial 12 size 640,480 '

> The initialization error seems to come from term/gd.trm when it discovers
> the default_font pointer is NULL. A FIXME comment just above this
> suggests it should "never happen," from which I surmise this isn't a
> known problem. If I force GD_NEED_LOCAL_FONT_POINTERS to be undefined,
> the gd.trm initialization error goes away and so does the crashing. I'm
> not sure what else, if anything, this breaks.
> 
> What does GD_NEED_LOCAL_FONT_POINTERS do? How are font pointers used 
> and what does it mean for one to be local?

This has to do with linking to a particular windows version of libgd.  
Apparently when building a shared libgd.dll for windows,
there are two different ways to define font pointers.  The conditional
flag GD_NEED_LOCAL_FONT_POINTERS in gnuplot is supposed to signal which
of these two methods the Windows *.dll is using.  My guess is that your
copy of libgd.dll uses one method, while your copy of gnuplot assumes
the other. But that's only a guess. I don't work with Windows, and I'm
hazy on the details.    

On the other hand, these pointers are only used if the terminal falls
back to using a default internal font.  Since you are requesting a specific
external font  "Arial,12", I don't immediately see why this error 
would trigger.  If you can trap a specific source code line number at
which the crash triggers, that might help.


-- 
Ethan A Merritt