Re: Octave 3.1.55: printing to pdf

[Ben A. <bpa...@ma...>]

On Apr 5, 2009, at 2:14 PM, Ethan A Merritt wrote:

> On Sunday 05 April 2009, Ben Abbott wrote:
>>
>> On Apr 5, 2009, at 3:47 AM, Petr Mikulik wrote:
>>
>>> Printing to pdf (via gnuplot backend) is broken in Octave 3.1.55
>>> even though
>>> gnuplot accepts "set term pdf" via "pdfcairo" terminal.
>>>
>>>
>>>> plot(1:100); print a.pdf -dpdf
>>>
>>> error: gnuplot_drawnow: the gnuplot terminal, "pdf", is not  
>>> available.
>>> error: called from:
>>> error:
>>> /opt/octave/octave-3.1.55/share/octave/3.1.55/m/plot/
>>> gnuplot_drawnow.m at
>>> line 72, column 7
>>>
>>>
>>> It seems that gnuplot_drawnow.m requires exact match of terminal
>>> names in
>>> 3.1.55. However, gnuplot names the pdf terminal "pdf" or "pdfcairo"
>>> according to the library it was compiled against. In both cases "set
>>> term
>>> pdf" works.
>>>
>>> I think gnuplot_drawnow.m should test presence of "pdfcairo" if
>>> "pdf" has
>>> not been found.
>>>
>>> If I try
>>> 	print zz.png -dpngcairo
>>> 	print zz.pdf -dpdfcairo
>>> it produces these two files:
>>> 	pngcairo:zz.png
>>> 	pdfcairo:zz.pdf
>>> Why the prefix there?
>>>
>>> ---
>>> PM
>>
>> Petr,
>>
>> For "set term png" if there is no "png" present does gnuplot
>> substitute "pngcairo" as well?
>
> yes
>
>> I notice the cairo terminals default options are different from the
>> non-cairo terminals. Specifically, there is no default font-name
>> specified, in GPVAL_TERMOPTIONS, for the cairo terminals. This will
>> interfere with the rendering of different font-sizes when the
>> anonymous font-name "*" is associated to an Octave text object.
>
> The cairo terminals default to font "Sans".
> Why does this make a difference?

Octave would prefer to specify the font-name and font-size for all  
text objects. Unfortunately, Octave has no way to determining that  
font-names are available to a particular gnuplot terminal. If a font- 
name is specified that a terminal does not have access to, errors/ 
warnings result. In addition, the text generally does not show up.

To alleviate this, the current implementation of Octave uses an  
anonymous default font-name, "*". When this anonymous font-name is  
associated with a text object,  neither the font-name or font-size are  
passed on to gnuplot. The exceptions to this are the x11 and wxt  
terminals which apparently have no problem with the fontname "*".

> Would you like this to be echoed back by "show term"?
> All gnuplot terminals should accept a font-size request with a blank  
> font
> name as referring to the current (perhaps default) font.
> E.g.
>     set term png enhanced font ",11"
>     set title "Big Title" font ",20"
> should give you the default font in size 11 points, and a title in the
> same font with size 20 points.

Ok! I'll prepare a changeset to fix how Octave handles a font-name of  
"*".

Thanks for the information. This will simplify things quite a bit.

Ben