From c76219a37d471c38fc22f804973f1b9f4bb201e6 Mon Sep 17 00:00:00 2001
From: Holger Vogt <holger.vogt@uni-due.de>
Date: Sun, 9 Aug 2026 14:15:15 +0200
Subject: [PATCH] pyplot: If on MSVC the top graph limit is slightly less (due
 to double precision deviations) than the vector contents, the graph will not
 be plotted in this area. Therefore extend the limits a bit (0.5%). Gnuplot:
 Use snprintf instead of sprintf. Reduce limits extension to 0.005.

---
 src/frontend/plotting/gnuplot.c | 8 +++++---
 src/frontend/plotting/pyplot.c  | 7 +++++--
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/frontend/plotting/gnuplot.c b/src/frontend/plotting/gnuplot.c
index 662edb43f..b7b17f5b5 100644
--- a/src/frontend/plotting/gnuplot.c
+++ b/src/frontend/plotting/gnuplot.c
@@ -298,7 +298,10 @@ void ft_gnuplot(double *xlims, double *ylims,
         contours = has_contour_data(vecs);
     }
 
-    extrange = 0.05 * (ylims[1] - ylims[0]);
+    if (ylims)
+        extrange = 0.005 * (ylims[1] - ylims[0]);
+    else
+        extrange = 0.;
 
     if (!cp_getvar("gnuplot_terminal", CP_STRING,
             terminal, sizeof(terminal))) {
@@ -626,8 +629,7 @@ void ft_gnuplot(double *xlims, double *ylims,
 
 #if defined(__MINGW32__) || defined(_MSC_VER)
     /* for external fcn system() */
-    // (void) sprintf(buf, "start /B wgnuplot %s -" ,  filename_plt);
-    (void) sprintf(buf, "start /B wgnuplot -persist %s " ,  filename_plt);
+    (void) snprintf(buf, sizeof(buf), "start /B wgnuplot -persist %s " ,  filename_plt);
     _flushall();
 #else
     /* for external fcn system() from LINUX environment */
diff --git a/src/frontend/plotting/pyplot.c b/src/frontend/plotting/pyplot.c
index 16dd1d3ce..cc86313ce 100644
--- a/src/frontend/plotting/pyplot.c
+++ b/src/frontend/plotting/pyplot.c
@@ -278,8 +278,11 @@ void ft_pyplot(double *xlims, double *ylims,
         fprintf(file, "    _ax.grid(True, which='both')\n");
     if (xlims)
         fprintf(file, "    _ax.set_xlim(%e, %e)\n", xlims[0], xlims[1]);
-    if (ylims && !ylog)
-        fprintf(file, "    _ax.set_ylim(%e, %e)\n", ylims[0], ylims[1]);
+    /* expand the limits a little (0.5%) to avoid double precision deviation on Windows */
+    if (ylims && !ylog) {
+        double extrange = (ylims[1] - ylims[0]) * 0.005;
+        fprintf(file, "    _ax.set_ylim(%e, %e)\n", ylims[0] - extrange, ylims[1] + extrange);
+    }
     fprintf(file, "    _ax.legend()\n");
     if (xlabel) {
         text = cp_unquote(xlabel);