# HG changeset patch
# User Pantxo Diribarne <pantxo.diribarne@gmail.com>
# Date 1589637222 -7200
# Node ID 6e8d5c99263ccf244354600da367d70399092b26
# Parent  144d77f3f8296ab076bd017a0c751674d8514be8
Produce better looking TeX superscript and subscripts (bug #58376).

* NEWS: Announce changes.

* ft-text-renderer.cc (visit (text_element_superscript& e)): Scale down
font size 70% of the parent font size.  Shift baseline +40% of the parent
font size.
* ft-text-renderer.cc (visit (text_element_subscript& e)): Scale down font size
70% of the parent font size.  Shift baseline -15% of the parent font size.

* octave-svgconvert.cc (draw): Translate font-size string to double rather than
to int.

diff -r 144d77f3f829 -r 6e8d5c99263c NEWS
--- a/NEWS	Sun May 17 14:01:42 2020 -0700
+++ b/NEWS	Sat May 16 15:53:42 2020 +0200
@@ -39,6 +39,10 @@
 
 - Support for Qt4 for graphics and the GUI has been removed.
 
+- The placement of text subscripts and superscripts has been
+re-engineered and now produces visually attractive results similar to
+Latex.
+
 ### Matlab compatibility
 
 - The function `griddata` now implements the "v4" Biharmonic Spline
diff -r 144d77f3f829 -r 6e8d5c99263c libinterp/corefcn/ft-text-renderer.cc
--- a/libinterp/corefcn/ft-text-renderer.cc	Sun May 17 14:01:42 2020 -0700
+++ b/libinterp/corefcn/ft-text-renderer.cc	Sat May 16 15:53:42 2020 +0200
@@ -1099,16 +1099,16 @@
     int saved_line_yoffset = line_yoffset;
     int saved_yoffset = yoffset;
 
+    double sz = font.get_size ();
+
+    // Reducing font size by 70% produces decent results.
     set_font (font.get_name (), font.get_weight (), font.get_angle (),
-              font.get_size () - 2);
+              std::max (5.0, sz * 0.7));
 
     if (font.is_valid ())
       {
-        int h = font.get_face ()->size->metrics.height >> 6;
-
-        // Shifting the baseline by 2/3 the font height seems to produce
-        // decent result.
-        yoffset -= (h * 2) / 3;
+        // Shifting the baseline by 15% of the font size gives decent results.
+        yoffset -= std::ceil (sz * 0.15);
 
         if (mode == MODE_BBOX)
           update_line_bbox ();
@@ -1130,16 +1130,16 @@
     int saved_line_yoffset = line_yoffset;
     int saved_yoffset = yoffset;
 
+    double sz = font.get_size ();
+
+    // Reducing font size by 70% produces decent results.
     set_font (font.get_name (), font.get_weight (), font.get_angle (),
-              font.get_size () - 2);
+              std::max (5.0, sz * 0.7));
 
     if (saved_font.is_valid ())
       {
-        int s_asc = saved_font.get_face ()->size->metrics.ascender >> 6;
-
-        // Shifting the baseline by 2/3 base font ascender seems to produce
-        // decent result.
-        yoffset += (s_asc * 2) / 3;
+        // Shifting the baseline by 40% of the font size gives decent results.
+        yoffset += std::ceil (sz * 0.4);
 
         if (mode == MODE_BBOX)
           update_line_bbox ();
diff -r 144d77f3f829 -r 6e8d5c99263c src/octave-svgconvert.cc
--- a/src/octave-svgconvert.cc	Sun May 17 14:01:42 2020 -0700
+++ b/src/octave-svgconvert.cc	Sat May 16 15:53:42 2020 +0200
@@ -396,9 +396,9 @@
           if (! str.isEmpty () && str != "normal")
             font.setStyle (QFont::StyleItalic);
 
-          int sz = elt.attribute ("font-size").toInt ();
-          if (sz > 0)
-            font.setPixelSize (sz);
+          str = elt.attribute ("font-size");
+          if (! str.isEmpty ())
+            font.setPixelSize (str.toDouble ());
 
           painter.setFont (font);
 
@@ -459,9 +459,9 @@
                 font.setStyle (QFont::StyleNormal);
             }
 
-          int sz = elt.attribute ("font-size").toInt ();
-          if (sz > 0)
-            font.setPixelSize (sz);
+          str = elt.attribute ("font-size");
+          if (! str.isEmpty ())
+            font.setPixelSize (str.toDouble ());
 
           painter.setFont (font);