[font/util] Add emboldening API, --font-bold

Needs documentation.

src/hb-font.cc

@@ -1772,8 +1772,12 @@ DEFINE_NULL_INSTANCE (hb_font_t) =
 
   1000, /* x_scale */
   1000, /* y_scale */
-  0., /* slant */
-  0., /* slant_xy; */
+  0.f, /* x_embolden */
+  0.f, /* y_embolden */
+  0, /* x_shift */
+  0, /* y_shift */
+  0.f, /* slant */
+  0.f, /* slant_xy; */
   1.f, /* x_multf */
   1.f, /* y_multf */
   1<<16, /* x_mult */
@@ -1895,6 +1899,8 @@ hb_font_create_sub_font (hb_font_t *parent)
 
   font->x_scale = parent->x_scale;
   font->y_scale = parent->y_scale;
+  font->x_embolden = parent->x_embolden;
+  font->y_embolden = parent->y_embolden;
   font->slant = parent->slant;
   font->x_ppem = parent->x_ppem;
   font->y_ppem = parent->y_ppem;
@@ -2442,6 +2448,30 @@ hb_font_get_ptem (hb_font_t *font)
   return font->ptem;
 }
 
+void
+hb_font_set_synthetic_bold (hb_font_t *font, float x_embolden, float y_embolden)
+{
+  if (hb_object_is_immutable (font))
+    return;
+
+  if (font->x_embolden == x_embolden &&
+      font->y_embolden == y_embolden)
+    return;
+
+  font->serial++;
+
+  font->x_embolden = x_embolden;
+  font->y_embolden = y_embolden;
+  font->mults_changed ();
+}
+
+void
+hb_font_get_synthetic_bold (hb_font_t *font, float *x_embolden, float *y_embolden)
+{
+  if (x_embolden) *x_embolden = font->x_embolden;
+  if (y_embolden) *y_embolden = font->y_embolden;
+}
+
 /**
  * hb_font_set_synthetic_slant:
  * @font: #hb_font_t to work upon

src/hb-font.h

@@ -1131,6 +1131,12 @@ hb_font_set_ptem (hb_font_t *font, float ptem);
 HB_EXTERN float
 hb_font_get_ptem (hb_font_t *font);
 
+HB_EXTERN void
+hb_font_set_synthetic_bold (hb_font_t *font, float x_embolden, float y_embolden);
+
+HB_EXTERN void
+hb_font_get_synthetic_bold (hb_font_t *font, float *x_embolden, float *y_embolden);
+
 HB_EXTERN void
 hb_font_set_synthetic_slant (hb_font_t *font, float slant);
 

src/hb-font.hh

@@ -113,8 +113,15 @@ struct hb_font_t
 
   int32_t x_scale;
   int32_t y_scale;
+
+  float x_embolden;
+  float y_embolden;
+  int32_t x_shift; /* x_embolden, in scaled units. */
+  int32_t y_shift; /* y_embolden, in scaled units. */
+
   float slant;
   float slant_xy;
+
   float x_multf;
   float y_multf;
   int64_t x_mult;
@@ -666,12 +673,17 @@ struct hb_font_t
   void mults_changed ()
   {
     float upem = face->get_upem ();
+
     x_multf = x_scale / upem;
     y_multf = y_scale / upem;
     bool x_neg = x_scale < 0;
     x_mult = (x_neg ? -((int64_t) -x_scale << 16) : ((int64_t) x_scale << 16)) / upem;
     bool y_neg = y_scale < 0;
     y_mult = (y_neg ? -((int64_t) -y_scale << 16) : ((int64_t) y_scale << 16)) / upem;
+
+    x_shift = roundf (x_scale * x_embolden);
+    y_shift = roundf (y_scale * y_embolden);
+
     slant_xy = y_scale ? slant * x_scale / y_scale : 0.f;
 
     data.fini ();

src/hb-ft.cc

@@ -844,9 +844,7 @@ hb_ft_draw_glyph (hb_font_t *font,
 
   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_EmboldenXY (&ft_face->glyph->outline, font->x_shift, font->y_shift);
   FT_Outline_Decompose (&ft_face->glyph->outline,
 			&outline_funcs,
 			&draw_session);

src/hb-ot-font.cc

@@ -475,9 +475,7 @@ hb_ot_draw_glyph (hb_font_t *font,
 #endif
   {}
 
-  float xstr = font->x_scale / 20;
-  float ystr = font->y_scale / 20;
-  outline.embolden (xstr, ystr);
+  outline.embolden (font->x_shift, font->y_shift);
   outline.replay (draw_funcs, draw_data);
 
 }

util/font-options.hh

@@ -63,6 +63,8 @@ struct font_options_t : face_options_t
   int x_ppem = 0;
   int y_ppem = 0;
   double ptem = 0.;
+  double x_embolden = 0.;
+  double y_embolden = 0.;
   double slant = 0.;
   unsigned int subpixel_bits = SUBPIXEL_BITS;
   mutable double font_size_x = DEFAULT_FONT_SIZE;
@@ -101,6 +103,7 @@ font_options_t::post_parse (GError **error)
   hb_font_set_ppem (font, x_ppem, y_ppem);
   hb_font_set_ptem (font, ptem);
 
+  hb_font_set_synthetic_bold (font, (float) x_embolden, (float) y_embolden);
   hb_font_set_synthetic_slant (font, slant);
 
   int scale_x = (int) scalbnf (font_size_x, subpixel_bits);
@@ -245,6 +248,24 @@ parse_font_ppem (const char *name G_GNUC_UNUSED,
   }
 }
 
+static gboolean
+parse_font_bold (const char *name G_GNUC_UNUSED,
+		 const char *arg,
+		 gpointer    data,
+		 GError    **error G_GNUC_UNUSED)
+{
+  font_options_t *font_opts = (font_options_t *) data;
+  switch (sscanf (arg, "%lf%*[ ,]%lf", &font_opts->x_embolden, &font_opts->y_embolden)) {
+    case 1: font_opts->y_embolden = font_opts->x_embolden; HB_FALLTHROUGH;
+    case 2: return true;
+    default:
+      g_set_error (error, G_OPTION_ERROR, G_OPTION_ERROR_BAD_VALUE,
+		   "%s argument should be one or two space-separated numbers",
+		   name);
+      return false;
+  }
+}
+
 void
 font_options_t::add_options (option_parser_t *parser)
 {
@@ -286,7 +307,9 @@ font_options_t::add_options (option_parser_t *parser)
 			      G_OPTION_ARG_CALLBACK,	(gpointer) &parse_font_ppem,	"Set x,y pixels per EM (default: 0; disabled)",	"1/2 integers"},
     {"font-ptem",	0, font_size_flags,
 			      G_OPTION_ARG_DOUBLE,	&this->ptem,			"Set font point-size (default: 0; disabled)",	"point-size"},
-    {"font-slant",	0, 0,
+    {"font-bold",	0, font_size_flags,
+			      G_OPTION_ARG_CALLBACK,	(gpointer) &parse_font_bold,	"Set synthetic bold (default: 0)",		"1/2 numbers; eg. 0.05"},
+    {"font-slant",	0, font_size_flags,
 			      G_OPTION_ARG_DOUBLE,	&this->slant,			"Set synthetic slant (default: 0)",		 "slant ratio; eg. 0.2"},
     {"font-funcs",	0, 0, G_OPTION_ARG_STRING,	&this->font_funcs,		text,						"impl"},
     {"sub-font",	0, G_OPTION_FLAG_HIDDEN,