--- a/scripts/plot/util/print.m	Mon Jan 30 18:55:51 2023 +0100
+++ b/scripts/plot/util/print.m	Tue Jan 31 20:11:12 2023 +0100
@@ -157,6 +157,20 @@
 ## Caution: If Octave was built against Qt version earlier than 5.13,
 ## @option{-svgconvert} may lead to inaccurate rendering of image objects.
 ##
+## @item -polymerge
+## @itemx -nopolymerge
+## @itemx -polymerge-all
+##   When using the SVG based backend @option{-svgconvert}, faces are rendered
+## as triangles.  In some cases, some viewers might display fine lines where
+## those triangles share an edge.  These options control whether all triangles
+## that share edges are merged into polygons (@option{-polymerge-all} which
+## might take some time for graphics consisting of many triangles -- including
+## line markers), only consecutive polygons are merged (@option{-polymerge}),
+## or no triangles are merged at all (@option{-no-polymerge}).  By default,
+## only consecutive triangles sharing an edge are merged, unless the printed
+## figure contains patch or surface graphics objects in which case all
+## triangles that are sharing an edge are merged.
+##
 ## @item  -portrait
 ## @itemx -landscape
 ##   Specify the orientation of the plot for printed output.
@@ -1160,7 +1174,8 @@
     cmd = sprintf ('%s - %%s %3.2f "%s" %d "%%s"', ...
                    undo_string_escapes (opts.svgconvert_binary), ...
                    get (0, "screenpixelsperinch"), ...
-                   undo_string_escapes (fullfile (fontdir, "FreeSans.otf")), 1);
+                   undo_string_escapes (fullfile (fontdir, "FreeSans.otf")),
+                   opts.polymerge);
 
     if (opts.debug)
       fprintf ("svgconvert command: '%s'\n", cmd);

--- a/scripts/plot/util/private/__print_parse_opts__.m	Mon Jan 30 18:55:51 2023 +0100
+++ b/scripts/plot/util/private/__print_parse_opts__.m	Tue Jan 31 20:11:12 2023 +0100
@@ -59,6 +59,7 @@
   arg_st.ghostscript.antialiasing_textalphabits = 4;
   arg_st.ghostscript.antialiasing_graphicsalphabits = 1;
   arg_st.lpr_binary = __quote_path__ (__find_binary__ ("lpr"));
+  arg_st.polymerge = 1;
   arg_st.name = "";
   arg_st.orientation = "";
   arg_st.pstoedit_binary = __quote_path__ (__find_binary__ ("pstoedit"));
@@ -88,6 +89,11 @@
     varargin(1) = [];
   endif
 
+  if (! isempty (findall (arg_st.figure, "type", "patch", ...
+                          "-or", "type", "surface")))
+    arg_st.polymerge = 2;
+  endif
+
   for i = 1:numel (varargin)
     if (! ischar (varargin{i}) && ! iscellstr (varargin{i}))
       error ("print: input arguments must be a graphics handle or strings.");
@@ -127,6 +133,12 @@
         arg_st.svgconvert = true;
       elseif (strcmp (arg, "-nosvgconvert"))
         arg_st.svgconvert = false;
+      elseif (strcmp (arg, "-polymerge"))
+        arg_st.polymerge = 1;
+      elseif (strcmp (arg, "-nopolymerge"))
+        arg_st.polymerge = 0;
+      elseif (strcmp (arg, "-polymerge-all"))
+        arg_st.polymerge = 2;
       elseif (strcmp (arg, "-textspecial"))
         arg_st.special_flag = "textspecial";
       elseif (strcmp (arg, "-fillpage"))

--- a/src/octave-svgconvert.cc	Mon Jan 30 18:55:51 2023 +0100
+++ b/src/octave-svgconvert.cc	Tue Jan 31 20:11:12 2023 +0100
@@ -161,10 +161,12 @@
   void reset ()
   { m_polygons.clear (); }
 
-  QList<QPolygonF> reconstruct ()
+  QList<QPolygonF> reconstruct (int reconstruct_level)
   {
     if (m_polygons.isEmpty ())
       return QList<QPolygonF> ();
+    else if (reconstruct_level < 2)
+      return m_polygons;
 
     // Once a polygon has been merged to another, it is marked unsuded
     QVector<bool> unused;
@@ -749,7 +751,7 @@
     parent_elt.removeChild (orig.at (ii));
 }
 
-void reconstruct_polygons (QDomElement& parent_elt)
+void reconstruct_polygons (QDomElement& parent_elt, int reconstruct_level)
 {
   QDomNodeList nodes = parent_elt.childNodes ();
   QColor current_color;
@@ -787,7 +789,8 @@
               if (color != current_color)
                 {
                   // Reconstruct the previous series of triangles
-                  QList<QPolygonF> polygons = current_polygon.reconstruct ();
+                  QList<QPolygonF> polygons
+                    = current_polygon.reconstruct (reconstruct_level);
                   collection.push_back (QPair<QList<QDomNode>,QList<QPolygonF> >
                                         (replaced_nodes, polygons));
 
@@ -806,19 +809,20 @@
         {
           if (current_polygon.count ())
             {
-              QList<QPolygonF> polygons = current_polygon.reconstruct ();
+              QList<QPolygonF> polygons = current_polygon.reconstruct (reconstruct_level);
               collection.push_back (QPair<QList<QDomNode>,QList<QPolygonF> >
                                     (replaced_nodes, polygons));
               replaced_nodes.clear ();
               current_polygon.reset ();
             }
-          reconstruct_polygons (elt);
+          reconstruct_polygons (elt, reconstruct_level);
         }
     }
 
   // Finish
   collection.push_back (QPair<QList<QDomNode>,QList<QPolygonF> >
-                        (replaced_nodes, current_polygon.reconstruct ()));
+                          (replaced_nodes,
+                           current_polygon.reconstruct (reconstruct_level)));
 
   for (int ii = 0; ii < collection.count (); ii++)
     replace_polygons (parent_elt, collection[ii].first, collection[ii].second);
@@ -876,7 +880,10 @@
 * fmt: format of the output file. May be one of pdf or svg\n\
 * dpi: device dependent resolution in screen pixel per inch\n\
 * font: specify a file name for the default FreeSans font\n\
-* reconstruct: specify whether to reconstruct triangle to polygons (0 or 1)\n\
+* reconstruct: specify whether to reconstruct triangle to polygons\n\
+  0: no reconstruction (merging) of polygons\n\
+  1: merge consecutive triangles if they share an edge\n\
+  2: merge all triangles that share edges (might take a long time)\n\
 * outfile: output file name\n";
 
   if (strcmp (argv[1], "-h") == 0)
@@ -977,8 +984,9 @@
     }
 
   // Do basic polygons reconstruction
-  if (QString (argv[5]).toInt ())
-    reconstruct_polygons (root);
+  int reconstruct_level = QString (argv[5]).toInt ();
+  if (reconstruct_level)
+    reconstruct_polygons (root, reconstruct_level);
 
   // Add custom properties to SVG
   add_custom_properties (root);