Re: [PATCH] Implement SVG plotting

[Jeroen Demeyer <jdemeyer@cage.ugent.be>]

On 2017-01-14 17:56, Bill Allombert wrote:
> How do you envision SVG to be used under GP ?
>
> How libpari program will be able to use graphics ?

1. Graphics in general:

First of all, my latest version of my patches (see the jeroen-svg 
branch) adds a new option to pari_init() called INIT_GRAPHm. This option 
should be used whenever graphics are needed.

Second, some variant of PARI_get_plot_FOO() needs to be called to select 
the plotting backend. For example, PARI_get_plot_X() for X11 or 
PARI_get_plot_svg() for SVG. It is legal to change the plotting backend 
at runtime by calling a different PARI_get_plot_BAR() function.

Now, the PARI plotting functions can be called.


2. SVG specifics:

For SVG plotting, there is a new callback function
void cb_plot_svg(const char *svg)
which will be called whenever an SVG image is produced. The SVG code (as 
0-terminated string) will be passed as the argument. The application can 
then do whatever it wants. By default, cb_plot_svg=pari_puts so the SVG 
will simply be printed.


3. gp specifics:

Within gp, there should probably be a new default to select the plotting 
backend. Something like
default(graphic, "X")
for X11 plotting for example. Then sd_graphic() should call the 
corresponding PARI_get_plot_FOO() function.
For SVG plotting, I suggest to write to a file (analogously to ps 
plotting). So there should be a default(svgfile) and a callback function 
which writes its argument to the svgfile.


4. psplot

Currently, ps plotting is implemented independently from other plotting 
engines with separate functions. In the future, this should probably be 
changed and it should just be another plotting backend.