gd.trm png_state.default_font

[Tait]

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 '
        gnuplot> set term windows
        Terminal type set to 'windows'
        Options are 'color noenhanced'
        gnuplot> set term png
        Terminal type set to 'png'
        Options are 'nocrop font arial 12 size 640,480 '
        gnuplot> set output 'sinx.png'
        gnuplot> plot sin(x)
        gnuplot> unset output
        gnuplot> set term windows enhanced
        Terminal type set to 'windows'
        Options are 'color enhanced'
        gnuplot>


If I attempt to plot after the _first_ "set term png" gnuplot will crash,
every time. If I wait until after the "caught initialization" error as
above, plotting works fine -- valid PNG results and no crash. (There are
certain combinations of options I can give to the PNG terminal to avoid
this crash, but I haven't narrowed down exactly what they are.)

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?

Tait


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[Ethan Merritt]

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

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[Petr Mikulik]

> 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
>
> If I attempt to plot after the _first_ "set term png" gnuplot will crash,
> every time. If I wait until after the "caught initialization" error as
> above, plotting works fine -- valid PNG results and no crash. (There are
> certain combinations of options I can give to the PNG terminal to avoid
> this crash, but I haven't narrowed down exactly what they are.)

I've compiled gnuplot with static gd library and it works correctly.

---
PM

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