[font] Towards implementing emboldening

src/hb-draw-embolden.hh

@@ -0,0 +1,349 @@
+/*
+ * Copyright © 2023  Behdad Esfahbod
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#ifndef HB_DRAW_EMBOLDEN_HH
+#define HB_DRAW_EMBOLDEN_HH
+
+#include "hb.hh"
+
+#include "hb-draw.hh"
+
+
+struct hb_contour_point_t
+{
+  enum class type_t
+  {
+    MOVE_TO,
+    LINE_TO,
+    QUADRATIC_TO,
+    CUBIC_TO,
+  };
+
+  hb_contour_point_t (float x, float y, type_t type) :
+    x (x), y (y), type (type) {}
+
+  float x, y;
+  type_t type;
+};
+
+using hb_contour_t = hb_vector_t<hb_contour_point_t>;
+
+template <typename context_t>
+struct hb_filter_outline_t
+{
+  void replay (hb_draw_funcs_t *pen, void *pen_data)
+  {
+    hb_draw_state_t st = HB_DRAW_STATE_DEFAULT;
+
+    unsigned first = 0;
+    for (unsigned contour : contours)
+    {
+      auto it = points.as_array ().sub_array (first, contour - first);
+      while (it)
+      {
+	hb_contour_point_t p1 = *it++;
+	switch (p1.type)
+	{
+	  case hb_contour_point_t::type_t::MOVE_TO:
+	  {
+	    pen->move_to (pen_data, st,
+			     p1.x, p1.y);
+	  }
+	  break;
+	  case hb_contour_point_t::type_t::LINE_TO:
+	  {
+	    pen->line_to (pen_data, st,
+			     p1.x, p1.y);
+	  }
+	  break;
+	  case hb_contour_point_t::type_t::QUADRATIC_TO:
+	  {
+	    hb_contour_point_t p2 = *it++;
+	    pen->quadratic_to (pen_data, st,
+				  p1.x, p1.y,
+				  p2.x, p2.y);
+	  }
+	  break;
+	  case hb_contour_point_t::type_t::CUBIC_TO:
+	  {
+	    hb_contour_point_t p2 = *it++;
+	    hb_contour_point_t p3 = *it++;
+	    pen->cubic_to (pen_data, st,
+			      p1.x, p1.y,
+			      p2.x, p2.y,
+			      p3.x, p3.y);
+	  }
+	  break;
+	}
+      }
+      pen->close_path (pen_data, st);
+      first = contour;
+    }
+  }
+
+  hb_vector_t<hb_contour_point_t> points;
+  hb_vector_t<unsigned> contours;
+};
+
+template <typename context_t>
+static void
+hb_filter_outline_move_to (hb_draw_funcs_t *dfuncs HB_UNUSED,
+			   void *data,
+			   hb_draw_state_t *st,
+			   float to_x, float to_y,
+			   void *user_data HB_UNUSED)
+{
+  context_t *c = (context_t *) data;
+
+  c->points.push (hb_contour_point_t {to_x, to_y, hb_contour_point_t::type_t::MOVE_TO});
+}
+
+template <typename context_t>
+static void
+hb_filter_outline_line_to (hb_draw_funcs_t *dfuncs HB_UNUSED,
+			   void *data,
+			   hb_draw_state_t *st,
+			   float to_x, float to_y,
+			   void *user_data HB_UNUSED)
+{
+  context_t *c = (context_t *) data;
+
+  c->points.push (hb_contour_point_t {to_x, to_y, hb_contour_point_t::type_t::LINE_TO});
+}
+
+template <typename context_t>
+static void
+hb_filter_outline_quadratic_to (hb_draw_funcs_t *dfuncs HB_UNUSED,
+				void *data,
+				hb_draw_state_t *st,
+				float control_x, float control_y,
+				float to_x, float to_y,
+				void *user_data HB_UNUSED)
+{
+  context_t *c = (context_t *) data;
+
+  c->points.push (hb_contour_point_t {control_x, control_y, hb_contour_point_t::type_t::QUADRATIC_TO});
+  c->points.push (hb_contour_point_t {to_x, to_y, hb_contour_point_t::type_t::QUADRATIC_TO});
+}
+
+template <typename context_t>
+static void
+hb_filter_outline_cubic_to (hb_draw_funcs_t *dfuncs HB_UNUSED,
+			    void *data,
+			    hb_draw_state_t *st,
+			    float control1_x, float control1_y,
+			    float control2_x, float control2_y,
+			    float to_x, float to_y,
+			    void *user_data HB_UNUSED)
+{
+  context_t *c = (context_t *) data;
+
+  c->points.push (hb_contour_point_t {control1_x, control1_y, hb_contour_point_t::type_t::CUBIC_TO});
+  c->points.push (hb_contour_point_t {control2_x, control2_y, hb_contour_point_t::type_t::CUBIC_TO});
+  c->points.push (hb_contour_point_t {to_x, to_y, hb_contour_point_t::type_t::CUBIC_TO});
+}
+
+template <typename context_t>
+static void
+hb_filter_outline_close_path (hb_draw_funcs_t *dfuncs HB_UNUSED,
+			      void *data,
+			      hb_draw_state_t *st,
+			      void *user_data HB_UNUSED)
+{
+  context_t *c = (context_t *) data;
+
+  c->contours.push (c->points.length);
+}
+
+
+struct hb_draw_embolden_context_t : hb_filter_outline_t<hb_draw_embolden_context_t>
+{
+  void operator () (float x_strength, float y_strength)
+  {
+    if (!x_strength && !y_strength) return;
+    if (!points) return;
+
+    x_strength /= 2.f;
+    y_strength /= 2.f;
+
+    bool orientation_negative = false;
+
+    struct vector_t
+    {
+      float normalize_len ()
+      {
+	float len = hypotf (x, y);
+	if (len)
+	{
+	  x /= len;
+	  y /= len;
+	}
+	return len;
+      }
+
+      float x, y;
+    };
+
+    signed first = 0;
+    for (unsigned c = 0; c < contours.length; c++)
+    {
+      vector_t in, out, anchor, shift;
+      float l_in, l_out, l_anchor = 0, l, q, d;
+
+      l_in = 0;
+      signed last = (int) contours[c] - 1;
+
+      /* pacify compiler */
+      in.x = in.y = anchor.x = anchor.y = 0;
+
+      /* Counter j cycles though the points; counter i advances only  */
+      /* when points are moved; anchor k marks the first moved point. */
+      for ( signed i = last, j = first, k = -1;
+	    j != i && i != k;
+	    j = j < last ? j + 1 : first )
+      {
+	if ( j != k )
+	{
+	  out.x = points[j].x - points[i].x;
+	  out.y = points[j].y - points[i].y;
+	  l_out = out.normalize_len ();
+
+	  if ( l_out == 0 )
+	    continue;
+	}
+	else
+	{
+	  out   = anchor;
+	  l_out = l_anchor;
+	}
+
+	if ( l_in != 0 )
+	{
+	  if ( k < 0 )
+	  {
+	    k        = i;
+	    anchor   = in;
+	    l_anchor = l_in;
+	  }
+
+	  d = in.x * out.x + in.y * out.y;
+
+	  /* shift only if turn is less than ~160 degrees */
+	  if ( d > -15.f/16.f )
+	  {
+	    d = d + 1.f;
+
+	    /* shift components along lateral bisector in proper orientation */
+	    shift.x = in.y + out.y;
+	    shift.y = in.x + out.x;
+
+	    if ( orientation_negative )
+	      shift.x = -shift.x;
+	    else
+	      shift.y = -shift.y;
+
+	    /* restrict shift magnitude to better handle collapsing segments */
+	    q = out.x * in.y - out.y * in.x;
+	    if ( orientation_negative )
+	      q = -q;
+
+	    l = hb_min (l_in, l_out);
+
+	    /* non-strict inequalities avoid divide-by-zero when q == l == 0 */
+	    if (x_strength * q <= l * d)
+	      shift.x = shift.x * x_strength / d;
+	    else
+	      shift.x = shift.x * l / q;
+
+
+	    if (y_strength * q <= l * d)
+	      shift.y = shift.y * y_strength / d;
+	    else
+	      shift.y = shift.y * l / q;
+	  }
+	  else
+	    shift.x = shift.y = 0;
+
+	  for ( ;
+		i != j;
+		i = i < last ? i + 1 : first )
+	  {
+	    points[i].x += x_strength + shift.x;
+	    points[i].y += y_strength + shift.y;
+	  }
+	}
+	else
+	  i = j;
+
+	in   = out;
+	l_in = l_out;
+      }
+
+      first = last + 1;
+    }
+  }
+
+  hb_draw_funcs_t *pen;
+  void *pen_data;
+  float x_strength, y_strength;
+};
+
+static inline void free_static_draw_embolden_funcs ();
+
+static struct hb_draw_embolden_funcs_lazy_loader_t : hb_draw_funcs_lazy_loader_t<hb_draw_embolden_funcs_lazy_loader_t>
+{
+  static hb_draw_funcs_t *create ()
+  {
+    hb_draw_funcs_t *funcs = hb_draw_funcs_create ();
+
+    using t = hb_draw_embolden_context_t;
+
+    hb_draw_funcs_set_move_to_func (funcs, hb_filter_outline_move_to<t>, nullptr, nullptr);
+    hb_draw_funcs_set_line_to_func (funcs, hb_filter_outline_line_to<t>, nullptr, nullptr);
+    hb_draw_funcs_set_quadratic_to_func (funcs, hb_filter_outline_quadratic_to<t>, nullptr, nullptr);
+    hb_draw_funcs_set_cubic_to_func (funcs, hb_filter_outline_cubic_to<t>, nullptr, nullptr);
+    hb_draw_funcs_set_close_path_func (funcs, hb_filter_outline_close_path<t>, nullptr, nullptr);
+
+    hb_draw_funcs_make_immutable (funcs);
+
+    hb_atexit (free_static_draw_embolden_funcs);
+
+    return funcs;
+  }
+} static_draw_embolden_funcs;
+
+static inline
+void free_static_draw_embolden_funcs ()
+{
+  static_draw_embolden_funcs.free_instance ();
+}
+
+static hb_draw_funcs_t *
+hb_draw_embolden_get_funcs ()
+{
+  return static_draw_embolden_funcs.get_unconst ();
+}
+
+
+#endif /* HB_DRAW_EMBOLDEN_HH */

src/hb-ft.cc

@@ -45,6 +45,7 @@
 #include FT_MULTIPLE_MASTERS_H
 #include FT_OUTLINE_H
 #include FT_TRUETYPE_TABLES_H
+#include FT_SYNTHESIS_H
 #if (FREETYPE_MAJOR*10000 + FREETYPE_MINOR*100 + FREETYPE_PATCH) >= 21300
 #include FT_COLOR_H
 #endif
@@ -815,7 +816,7 @@ _hb_ft_cubic_to (const FT_Vector *control1,
 }
 
 static void
-hb_ft_draw_glyph (hb_font_t *font HB_UNUSED,
+hb_ft_draw_glyph (hb_font_t *font,
 		  void *font_data,
 		  hb_codepoint_t glyph,
 		  hb_draw_funcs_t *draw_funcs, void *draw_data,
@@ -843,6 +844,9 @@ hb_ft_draw_glyph (hb_font_t *font HB_UNUSED,
 
   hb_draw_session_t draw_session (draw_funcs, draw_data, font->slant_xy);
 
+  hb_position_t xstr = font->x_scale / 20;
+  hb_position_t ystr = font->y_scale / 20;
+  FT_Outline_EmboldenXY (&ft_face->glyph->outline, xstr, ystr);
   FT_Outline_Decompose (&ft_face->glyph->outline,
 			&outline_funcs,
 			&draw_session);

src/hb-ot-font.cc

@@ -34,6 +34,7 @@
 #include "hb-font.hh"
 #include "hb-machinery.hh"
 #include "hb-ot-face.hh"
+#include "hb-draw-embolden.hh"
 
 #include "hb-ot-cmap-table.hh"
 #include "hb-ot-glyf-table.hh"
@@ -462,12 +463,23 @@ hb_ot_draw_glyph (hb_font_t *font,
 		  hb_draw_funcs_t *draw_funcs, void *draw_data,
 		  void *user_data)
 {
-  hb_draw_session_t draw_session (draw_funcs, draw_data, font->slant_xy);
+
-  if (font->face->table.glyf->get_path (font, glyph, draw_session)) return;
+  hb_draw_embolden_context_t emboldener;
+  auto *embolden_funcs = hb_draw_embolden_get_funcs ();
+
+  hb_draw_session_t draw_session (embolden_funcs, &emboldener, font->slant_xy);
+  if (!font->face->table.glyf->get_path (font, glyph, draw_session))
 #ifndef HB_NO_CFF
-  if (font->face->table.cff1->get_path (font, glyph, draw_session)) return;
+  if (!font->face->table.cff1->get_path (font, glyph, draw_session))
-  if (font->face->table.cff2->get_path (font, glyph, draw_session)) return;
+  if (!font->face->table.cff2->get_path (font, glyph, draw_session))
 #endif
+  {}
+
+  float xstr = font->x_scale / 20;
+  float ystr = font->y_scale / 20;
+  emboldener (xstr, ystr);
+  emboldener.replay (draw_funcs, draw_data);
+
 }
 #endif
 

src/hb-vector.hh

@@ -459,7 +459,7 @@ struct hb_vector_t
     length--;
   }
 
-  void shrink (int size_)
+  void shrink (int size_, bool shrink_memory = true)
   {
     unsigned int size = size_ < 0 ? 0u : (unsigned int) size_;
     if (size >= length)
@@ -467,6 +467,7 @@ struct hb_vector_t
 
     shrink_vector (size);
 
+    if (shrink_memory)
       alloc (size, true); /* To force shrinking memory if needed. */
   }