[80_6] Improving Radical Box Typesetting (#2118)

KeShih · web-flow · commit 3e4db4615f44 · 2024-10-13T17:16:50.000+08:00
## What Improving Fraction Box Typesetting. ## Why For some opentype math font, math table gives more precise information about typesetting radical. ## How to test your changes? Open `devel/80_6.tmu`. It is evident that the Asana Math and Fira Math opentype fonts have undergone changes, with significant adjustments in the spacing and positioning before and after the degree symbol. In contrast, the latter two hardcoded opentype fonts have remained unchanged. Before: ![image](https://github.com/user-attachments/assets/70946804-6b11-48e9-b975-a16b716d9697) After: ![image](https://github.com/user-attachments/assets/49e2a0a4-214d-487d-91e8-46a872a083dd)
diff --git a/devel/80_6.tmu b/devel/80_6.tmu
@@ -0,0 +1,40 @@
+<TMU|<tuple|1.0.4|1.2.9.3-rc2>>
+
+<style|<tuple|generic|chinese>>
+
+<\body>
+  Asana Math:
+
+  <\equation*>
+    <around*|{|<sqrt|1234|abc>|}><sqrt|1+<sqrt|2+<sqrt|3+<sqrt|4+<sqrt|5+<sqrt|6+<sqrt|7+<sqrt|8+\<cdots\>>>>>>>>>
+  </equation*>
+
+  Fira Math:
+
+  <\equation*>
+    <with|font|Fira Math|<around*|{|<sqrt|1234|abc>|}><sqrt|1+<sqrt|2+<sqrt|3+<sqrt|4+<sqrt|5+<sqrt|6+<sqrt|7+<sqrt|8+\<cdots\>>>>>>>>>>
+  </equation*>
+
+  TeX Gyre Pagella Math:
+
+  <\equation*>
+    <with|font|TeX Gyre Pagella Math|<around*|{|<sqrt|1234|abc>|}><sqrt|1+<sqrt|2+<sqrt|3+<sqrt|4+<sqrt|5+<sqrt|6+<sqrt|7+<sqrt|8+\<cdots\>>>>>>>>>>
+  </equation*>
+
+  \ TeX Gyre Schola Math:
+
+  <with|font|TeX Gyre Schola Math|<\equation*>
+    <around*|{|<sqrt|1234|abc>|}><sqrt|1+<sqrt|2+<sqrt|3+<sqrt|4+<sqrt|5+<sqrt|6+<sqrt|7+<sqrt|8+\<cdots\>>>>>>>>>
+  </equation*>>
+</body>
+
+<\initial>
+  <\collection>
+    <associate|font|Asana Math>
+    <associate|font-family|rm>
+    <associate|font-shape|italic>
+    <associate|math-font|math-dejavu>
+    <associate|page-medium|paper>
+    <associate|page-screen-margin|false>
+  </collection>
+</initial>
diff --git a/src/Graphics/Fonts/font.cpp b/src/Graphics/Fonts/font.cpp
@@ -109,6 +109,13 @@ font_rep::copy_math_pars (font fn) {
   frac_denom_disp_shift_down   = fn->frac_denom_disp_shift_down;
   frac_denom_gap_min           = fn->frac_denom_gap_min;
   frac_denom_disp_gap_min      = fn->frac_denom_disp_gap_min;
+  sqrt_ver_gap                 = fn->sqrt_ver_gap;
+  sqrt_ver_disp_gap            = fn->sqrt_ver_disp_gap;
+  sqrt_rule_thickness          = fn->sqrt_rule_thickness;
+  sqrt_extra_ascender          = fn->sqrt_extra_ascender;
+  sqrt_degree_rise_percent     = fn->sqrt_degree_rise_percent;
+  sqrt_kern_before_degree      = fn->sqrt_kern_before_degree;
+  sqrt_kern_after_degree       = fn->sqrt_kern_after_degree;
 }
 
 void
diff --git a/src/Graphics/Fonts/font.hpp b/src/Graphics/Fonts/font.hpp
@@ -75,19 +75,26 @@ struct font_rep : rep<font> {
   SI yshift;       // vertical script shift inside fractions
 
   // only for opentype fonts
-  SI upper_limit_gap_min;
-  SI upper_limit_baseline_rise_min;
-  SI lower_limit_gap_min;
-  SI lower_limit_baseline_drop_min;
-  SI frac_rule_thickness;
-  SI frac_num_shift_up;
-  SI frac_num_disp_shift_up;
-  SI frac_num_gap_min;
-  SI frac_num_disp_gap_min;
-  SI frac_denom_shift_down;
-  SI frac_denom_disp_shift_down;
-  SI frac_denom_gap_min;
-  SI frac_denom_disp_gap_min;
+  SI  upper_limit_gap_min;
+  SI  upper_limit_baseline_rise_min;
+  SI  lower_limit_gap_min;
+  SI  lower_limit_baseline_drop_min;
+  SI  frac_rule_thickness;
+  SI  frac_num_shift_up;
+  SI  frac_num_disp_shift_up;
+  SI  frac_num_gap_min;
+  SI  frac_num_disp_gap_min;
+  SI  frac_denom_shift_down;
+  SI  frac_denom_disp_shift_down;
+  SI  frac_denom_gap_min;
+  SI  frac_denom_disp_gap_min;
+  SI  sqrt_ver_gap;
+  SI  sqrt_ver_disp_gap;
+  SI  sqrt_rule_thickness;
+  SI  sqrt_extra_ascender;
+  int sqrt_degree_rise_percent;
+  SI  sqrt_kern_before_degree;
+  SI  sqrt_kern_after_degree;
 
   SI wpt;   // width of one point in font
   SI hpt;   // height of one point in font (usually wpt)
diff --git a/src/Plugins/Freetype/unicode_font.cpp b/src/Plugins/Freetype/unicode_font.cpp
@@ -477,6 +477,21 @@ unicode_font_rep::unicode_font_rep (string name, string family2, int size2,
           math_table->constants_table[fractionDenominatorGapMin]);
       frac_denom_disp_gap_min= design_unit_to_metric (
           math_table->constants_table[fractionDenominatorGapMin]);
+      // sqrt boxes
+      sqrt_ver_gap= design_unit_to_metric (
+          math_table->constants_table[radicalVerticalGap]);
+      sqrt_ver_disp_gap= design_unit_to_metric (
+          math_table->constants_table[radicalDisplayStyleVerticalGap]);
+      sqrt_rule_thickness= design_unit_to_metric (
+          math_table->constants_table[radicalRuleThickness]);
+      sqrt_extra_ascender= design_unit_to_metric (
+          math_table->constants_table[radicalExtraAscender]);
+      sqrt_degree_rise_percent=
+          math_table->constants_table[radicalDegreeBottomRaisePercent];
+      sqrt_kern_before_degree= design_unit_to_metric (
+          math_table->constants_table[radicalKernBeforeDegree]);
+      sqrt_kern_after_degree= design_unit_to_metric (
+          math_table->constants_table[radicalKernAfterDegree]);
     }
   }
 }
diff --git a/src/Typeset/Boxes/Composite/math_boxes.cpp b/src/Typeset/Boxes/Composite/math_boxes.cpp
@@ -177,7 +177,10 @@ sqrt_box_rep::sqrt_box_rep (path ip, box b1, box b2, box sqrtb, font fn2,
   SI by= sqrtb->y2 + dy;
   if (sqrtb->x2 - sqrtb->x4 > wline) dx-= (sqrtb->x2 - sqrtb->x4);
 
-  pencil rpen= pen->set_width (wline);
+  bool use_open_type= (fn->math_type == MATH_TYPE_OPENTYPE) &&
+                      (fn->sqrt_degree_rise_percent > 0);
+  pencil rpen= use_open_type ? pen->set_width (fn->sqrt_rule_thickness)
+                             : pen->set_width (wline);
   insert (b1, 0, 0);
   if (!is_nil (b2)) {
     SI X = -sqrtb->w ();
@@ -191,6 +194,13 @@ sqrt_box_rep::sqrt_box_rep (path ip, box b1, box b2, box sqrtb, font fn2,
       else if (occurs ("agella", fn->res_name)) Y+= (16 * bw) >> 3;
       else Y+= (15 * bw) >> 3;
     }
+    else if (use_open_type) {
+      Y+= fn->sqrt_degree_rise_percent * sqrtb->h () / 100;
+      M  = fn->sqrt_kern_after_degree;
+      sep= 0;
+      // we don't use it because it looks out of harmony
+      // b2->x1-= fn->sqrt_kern_before_degree;
+    }
     else {
       if (bh < 3 * bw) Y+= bh >> 1;
       else Y+= (bw * 3) >> 1;
@@ -203,7 +213,7 @@ sqrt_box_rep::sqrt_box_rep (path ip, box b1, box b2, box sqrtb, font fn2,
   position ();
   left_justify ();
   y1-= wline;
-  y2+= wline;
+  y2+= use_open_type ? fn->sqrt_extra_ascender : wline;
   x2+= sep >> 1;
 
   right_italic_restore (b1);
diff --git a/src/Typeset/Concat/concat_math.cpp b/src/Typeset/Concat/concat_math.cpp
@@ -11,6 +11,7 @@
 
 #include "analyze.hpp"
 #include "concater.hpp"
+#include "font.hpp"
 #include "packrat.hpp"
 
 using namespace moebius;
@@ -453,9 +454,9 @@ concater_rep::typeset_sqrt (tree t, path ip) {
     typeset_wide_sqrt (t, ip);
     return;
   }
-  box ind;
+  box  ind;
+  bool disp= env->display_style;
   if (N (t) == 2) {
-    bool disp= env->display_style;
     tree old;
     if (disp) old= env->local_begin (MATH_DISPLAY, "false");
     tree old_il= env->local_begin_script ();
@@ -467,8 +468,15 @@ concater_rep::typeset_sqrt (tree t, path ip) {
   font lfn = env->fn;
   bool stix= starts (lfn->res_name, "stix-");
   if (stix) lfn= rubber_font (lfn);
+  SI   gap= (3 * sep >> 1);
+  bool use_opentype=
+      (lfn->math_type == MATH_TYPE_OPENTYPE) && (lfn->sqrt_ver_gap > 0);
+  if (use_opentype) {
+    gap=
+        (disp ? lfn->sqrt_ver_disp_gap : lfn->sqrt_ver_gap) + (lfn->wline >> 1);
+  }
   box sqrtb= delimiter_box (decorate_left (ip), "<large-sqrt>", lfn, env->pen,
-                            b->y1, b->y2 + (3 * sep >> 1));
+                            b->y1, b->y2 + gap);
   if (stix)
     sqrtb= shift_box (decorate_left (ip), sqrtb, -env->fn->wline / 2,
                       -env->fn->wline / 3, false, true);
