[util] Add --font-slant

util/font-options.hh

@@ -58,6 +58,7 @@ struct font_options_t : face_options_t
   int x_ppem = 0;
   int y_ppem = 0;
   double ptem = 0.;
+  double slant = 0.;
   unsigned int subpixel_bits = SUBPIXEL_BITS;
   mutable double font_size_x = DEFAULT_FONT_SIZE;
   mutable double font_size_y = DEFAULT_FONT_SIZE;
@@ -94,6 +95,8 @@ 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_slant (font, slant);
+
   int scale_x = (int) scalbnf (font_size_x, subpixel_bits);
   int scale_y = (int) scalbnf (font_size_y, subpixel_bits);
   hb_font_set_scale (font, scale_x, scale_y);
@@ -265,6 +268,8 @@ 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, 0,
 			      G_OPTION_ARG_DOUBLE,	&this->ptem,			"Set font point-size (default: 0; disabled)",	"point-size"},
+    {"font-slant",	0, 0,
+			      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"},
     {"ft-load-flags",	0, 0, G_OPTION_ARG_INT,		&this->ft_load_flags,		"Set FreeType load-flags (default: 2)",		"integer"},
     {nullptr}