Re: crash bug in pdf terminal

[Daniel J S. <dan...@ie...>]

Daniel J Sebald wrote:

>> Another possible ingredient to this is the infamous signed vs. unsigned
>> confusion that infests practically all of gnuplot. 
>
>
> makes me wonder now.  They wouldn't say "too large" if in fact they 
> meant "negative" as the source of the problem.  So I think you are right.


I suspect that may be it.  The PDF library seems to be robust on the 
placement of text partially off the top of the canvas.  Also, the 
placement of tics far off the top:

set xtics offset 0,graph 10

causes no problems for PDFlib.

I think I see the issue now... what you all were probably talking about 
but I paid no attention.  In the terminal directory, the .trm files all 
have "unsigned" for coordinates, e.g.,

TERM_PUBLIC void
PDF_put_text (unsigned int x, unsigned int y, const char *str)

So, the question is, how is it that the PostScript terminal *works 
properly*?  Because it shouldn't.  It works because it is printing the 
unsigned numbers as signed:

    sprintf(abso, "%d %d M\n", x, y);
    sprintf(rel, "%d %d R\n", dx, dy);

So, the importance of the signed/unsigned issue isn't until its use. 
 (Conversion from signed int to unsigned int or vice versa doesn't do 
anything.  Only when it is interpretted is it important.)  The 
PDF_put_text fails because it has to do the conversion:

    double h = x, v = y;

near the top.


OK.  I'm getting the feeling this is case of someone having to go 
through the pain of changing all those "unsigned" coordinate values 
inside the terminal drivers to "signed".  At least I don't think it 
should wreck any working behavior.  It can only make bad behavior better.

If that's the case.  I'd suggest someone announce "I'm going to do this 
huge patch today, so nobody change anything in CVS for the day".  Then 
after that, we'll all shake the bugs out of the thing.

...

And I just tried a fix that sort of confirms the problem.  Inside the 
PDF terminal driver, I made the following change to the first few lines 
and the PDFlib abort goes away:

TERM_PUBLIC void
PDF_put_text (unsigned int ux, unsigned int uy, const char *str)
{
    char *alignment = NULL;
    int x = ux, y = uy;
    double h = x, v = y;

If people are happy with that as a fix, I'm fine with it too.  [Or it 
could be just

    double h = (signed) x, v = (signed) y;

if x and y are used no further down the road.]  Whether it says "signed" 
or "unsigned" in the function, no big deal to me.  However, who knows if 
all compilers behave the same regarding the signed/unsigned conversion.

Dan