2.0.13: dynamic linking with gnuplot

[Ilya Zakharevich <ilya@math.ohio-state.edu>]

Math::Pari Perl module uses a specific way to allow plotting: instead
of compiling plotnull.c (sp?) it compiles plotgnuplot.c with a special
flag -DDYNAMIC_PLOTTING.

When this flag is present, no external plotting functions are
mentioned in plotgnuplot.c (thus the effect is the same as for
plotnull.c - no external libraries are needed).  However, there is a
function which may be called to initialize 2 variables (sic, only two)
with addresses of a change-terminal function, and the GNUPLOT's table
of dispatch.

Thus the linking with high-resolution plotting is delayed until
runtime, when an external DLL may load GNUPLOT library, then call the
mentioned function in plotgnuplot.c with (now known) addresses.  

This is the way Math::Pari module works: it may load the Term::Gnuplot
low-level plotting Perl module, and initialize the variables with the
data taken from the Term::Gnuplot.

Unfortunately, the gnuplot-output-file setting I added breaks this
harmony, since set_output_file() is called directly, without
redirection.  The following patch fixes this.

Note that currently it is not possible to use the PARI function
plotfile() from Math::Pari.  An extra change to Term::Gnuplot is
needed - it needs to export the address of term_set_output().
However, Term::Gnuplot has an independent way to set the output file.

Enjoy,
Ilya

--- pari-2.0.13.alpha/src/graph/plotgnuplot.c~	Tue Dec 15 10:30:11 1998
+++ pari-2.0.13.alpha/src/graph/plotgnuplot.c	Thu Dec 17 02:28:56 1998
@@ -140,7 +140,7 @@ term_set(char *s)
 	reset();
   strcpy(pari_plot.name,s);
   if (!termset( s ))
-      err(talker,"error setting terminal \"\%s\"", s);
+      err(talker,"error setting terminal \"%s\"", s);
   do_init();				/* Init terminal. */
   setpointsize(pointsize);
 
--- pari-2.0.13.alpha/src/graph/Gnuplot.h~	Wed Dec  9 11:23:02 1998
+++ pari-2.0.13.alpha/src/graph/Gnuplot.h	Thu Dec 17 02:57:31 1998
@@ -281,11 +281,33 @@ static struct termentry dummy_term_tbl[]
 };
 static struct termentry *my_term_tbl = dummy_term_tbl;
 
+#  define term_set_output (*term_set_outputp)
+static void
+myterm_set_output(char *s)
+{
+    croak("Change terminal not implemented yet with dynamic gnuplot");
+}
+
+typedef void (*TSET_FP)(char *s);
+TSET_FP term_set_outputp = &myterm_set_output;
+
 /* This function should be called before any graphic code can be used... */
 set_term_funcp(FUNC_PTR change_p, struct termentry *term_p)
 {
     my_term_tbl = term_p;
     change_term_p = change_p;
+    /* XXXX Need to set term_set_outputp as well */
+}
+
+/* This function should be called before any graphic code can be used... */
+set_term_funcp3(FUNC_PTR change_p, struct termentry *term_p, TSET_FP tchange)
+{
+    my_term_tbl = term_p;
+    change_term_p = change_p;
+    if (tchange) {
+	term_set_outputp = tchange;
+    }
+    /* XXXX Need to set term_set_outputp as well */
 }
 
 #else /* !DYNAMIC_PLOTTING */