ft: Export FreeType synthesis options

Currently you can only specify that a cairo_ft_font_face_t should
synthesize a font (to make a bold variant) through an FcPattern. That is
direct consumers of the public cairo-ft API have no control over the
synthesize options.

Rectify this by creating some public API to allow control over the
synthesis flags, and include the ability to construct an oblique as
well an embolden font.

Based on a patch by Deokjin Kim <deokjin81.kim@samsung.com>.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

3 files changed, 124 insertions, 23 deletions

diff --git a/configure.ac b/configure.ac
index 3a438ee34..cedfebe4f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -494,7 +494,7 @@ if test "x$use_ft" = "xyes"; then
   AC_DEFINE_UNQUOTED(HAVE_FT_BITMAP_SIZE_Y_PPEM,$HAVE_FT_BITMAP_SIZE_Y_PPEM,
                      [FT_Bitmap_Size structure includes y_ppem field])
 
-  AC_CHECK_FUNCS(FT_GlyphSlot_Embolden FT_Load_Sfnt_Table FT_Library_SetLcdFilter)
+  AC_CHECK_FUNCS(FT_GlyphSlot_Embolden FT_GlyphSlot_Oblique FT_Load_Sfnt_Table FT_Library_SetLcdFilter)
 
   LIBS="$_save_libs"
   CFLAGS="$_save_cflags"
diff --git a/src/cairo-ft-font.c b/src/cairo-ft-font.c
index 0d0ac117c..af66de044 100644
--- a/src/cairo-ft-font.c
+++ b/src/cairo-ft-font.c
@@ -169,14 +169,10 @@ _cairo_ft_unscaled_font_keys_equal (const void *key_a,
 static void
 _cairo_ft_unscaled_font_fini (cairo_ft_unscaled_font_t *unscaled);
 
-enum _cairo_ft_extra_flags {
-    CAIRO_FT_OPTIONS_EMBOLDEN = 1 << 0
-};
-
 typedef struct _cairo_ft_options {
     cairo_font_options_t base;
     unsigned int load_flags; /* flags for FT_Load_Glyph */
-    unsigned int extra_flags; /* other flags that affect results */
+    unsigned int synth_flags;
 } cairo_ft_options_t;
 
 struct _cairo_ft_font_face {
@@ -1595,7 +1591,7 @@ _get_pattern_ft_options (FcPattern *pattern, cairo_ft_options_t *ret)
 
     _cairo_font_options_init_default (&ft_options.base);
     ft_options.load_flags = FT_LOAD_DEFAULT;
-    ft_options.extra_flags = 0;
+    ft_options.synth_flags = 0;
 
 #ifndef FC_EMBEDDED_BITMAP
 #define FC_EMBEDDED_BITMAP "embeddedbitmap"
@@ -1731,7 +1727,7 @@ _get_pattern_ft_options (FcPattern *pattern, cairo_ft_options_t *ret)
 	embolden = FcFalse;
 
     if (embolden)
-	ft_options.extra_flags |= CAIRO_FT_OPTIONS_EMBOLDEN;
+	ft_options.synth_flags |= CAIRO_FT_SYNTHESIZE_BOLD;
 
     *ret = ft_options;
 }
@@ -1811,7 +1807,7 @@ _cairo_ft_options_merge (cairo_ft_options_t *options,
     }
 
     options->load_flags = load_flags | load_target;
-    options->extra_flags = other->extra_flags;
+    options->synth_flags = other->synth_flags;
 }
 
 static cairo_status_t
@@ -2166,14 +2162,19 @@ _cairo_ft_scaled_glyph_init (void			*abstract_font,
 
     glyph = face->glyph;
 
-#if HAVE_FT_GLYPHSLOT_EMBOLDEN
     /*
-     * embolden glyphs if requested
+     * synthesize glyphs if requested
      */
-    if (scaled_font->ft_options.extra_flags & CAIRO_FT_OPTIONS_EMBOLDEN)
+#if HAVE_FT_GLYPHSLOT_EMBOLDEN
+    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_BOLD)
 	FT_GlyphSlot_Embolden (glyph);
 #endif
 
+#if HAVE_FT_GLYPHSLOT_OBLIQUE
+    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_OBLIQUE)
+	FT_GlyphSlot_Oblique (glyph);
+#endif
+
     if (vertical_layout)
 	_cairo_ft_scaled_glyph_vertical_layout_bearing_fix (scaled_font, glyph);
 
@@ -2318,12 +2319,13 @@ _cairo_ft_scaled_glyph_init (void			*abstract_font,
 		goto FAIL;
 	    }
 #if HAVE_FT_GLYPHSLOT_EMBOLDEN
-	    /*
-	     * embolden glyphs if requested
-	     */
-	    if (scaled_font->ft_options.extra_flags & CAIRO_FT_OPTIONS_EMBOLDEN)
+	    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_BOLD)
 		FT_GlyphSlot_Embolden (glyph);
 #endif
+#if HAVE_FT_GLYPHSLOT_OBLIQUE
+	    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_OBLIQUE)
+		FT_GlyphSlot_Oblique (glyph);
+#endif
 	    if (vertical_layout)
 		_cairo_ft_scaled_glyph_vertical_layout_bearing_fix (scaled_font, glyph);
 
@@ -2443,11 +2445,7 @@ static cairo_bool_t
 _cairo_ft_is_synthetic (void	        *abstract_font)
 {
     cairo_ft_scaled_font_t *scaled_font = abstract_font;
-
-    if (scaled_font->ft_options.extra_flags & CAIRO_FT_OPTIONS_EMBOLDEN)
-	return TRUE;
-    else
-	return FALSE;
+    return scaled_font->ft_options.synth_flags != 0;
 }
 
 static cairo_int_status_t
@@ -2841,7 +2839,7 @@ _cairo_ft_font_face_create (cairo_ft_unscaled_font_t *unscaled,
 	 prev_font_face = &font_face->next, font_face = font_face->next)
     {
 	if (font_face->ft_options.load_flags == ft_options->load_flags &&
-	    font_face->ft_options.extra_flags == ft_options->extra_flags &&
+	    font_face->ft_options.synth_flags == ft_options->synth_flags &&
 	    cairo_font_options_equal (&font_face->ft_options.base, &ft_options->base))
 	{
 	    if (font_face->base.status) {
@@ -3251,7 +3249,7 @@ cairo_ft_font_face_create_for_ft_face (FT_Face         face,
 	return (cairo_font_face_t *)&_cairo_font_face_nil;
 
     ft_options.load_flags = load_flags;
-    ft_options.extra_flags = 0;
+    ft_options.synth_flags = 0;
     _cairo_font_options_init_default (&ft_options.base);
 
     font_face = _cairo_ft_font_face_create (unscaled, &ft_options);
@@ -3261,6 +3259,72 @@ cairo_ft_font_face_create_for_ft_face (FT_Face         face,
 }
 
 /**
+ * cairo_ft_font_set_synthesize:
+ * @font_face: The #cairo_ft_font_face_t object to modify
+ * @synth_flags: the set of synthesis options to enable
+ *
+ * FreeType provides the ability to synthesize different glyphs from a base
+ * font, which is useful if you lack those glyphs from a true bold or oblique
+ * font.
+ *
+ * Since 1.12.
+ */
+void
+cairo_ft_font_face_set_synthesize (cairo_font_face_t *font_face,
+				   unsigned int synth_flags)
+{
+    cairo_ft_font_face_t *ft;
+
+    if (font_face->backend->type != CAIRO_FONT_TYPE_FT)
+	return;
+
+    ft = (cairo_ft_font_face_t *) font_face;
+    ft->ft_options.synth_flags |= synth_flags;
+}
+
+/**
+ * cairo_ft_font_unset_synthesize:
+ * @font_face: The #cairo_ft_font_face_t object to modify
+ * @synth_flags: the set of synthesis options to disable
+ *
+ * See cairo_ft_font_face_set_synthesize().
+ *
+ * Since 1.12.
+ */
+void
+cairo_ft_font_face_unset_synthesize (cairo_font_face_t *font_face,
+				     unsigned int synth_flags)
+{
+    cairo_ft_font_face_t *ft;
+
+    if (font_face->backend->type != CAIRO_FONT_TYPE_FT)
+	return;
+
+    ft = (cairo_ft_font_face_t *) font_face;
+    ft->ft_options.synth_flags &= ~synth_flags;
+}
+
+/**
+ * cairo_ft_font_get_synthesize:
+ * @font_face: The #cairo_ft_font_face_t object to query
+ *
+ * Returns the current set of synthesis options.
+ *
+ * Since 1.12.
+ */
+unsigned int
+cairo_ft_font_face_get_synthesize (cairo_font_face_t *font_face)
+{
+    cairo_ft_font_face_t *ft;
+
+    if (font_face->backend->type != CAIRO_FONT_TYPE_FT)
+	return 0;
+
+    ft = (cairo_ft_font_face_t *) font_face;
+    return ft->ft_options.synth_flags;
+}
+
+/**
  * cairo_ft_scaled_font_lock_face:
  * @scaled_font: A #cairo_scaled_font_t from the FreeType font backend. Such an
  *   object can be created by calling cairo_scaled_font_create() on a
diff --git a/src/cairo-ft.h b/src/cairo-ft.h
index 56d48c328..90fea31f3 100644
--- a/src/cairo-ft.h
+++ b/src/cairo-ft.h
@@ -56,6 +56,43 @@ cairo_public cairo_font_face_t *
 cairo_ft_font_face_create_for_ft_face (FT_Face         face,
 				       int             load_flags);
 
+/**
+ * cairo_ft_synthesize_t:
+ *
+ * A set of synthesis options to control how FreeType renders the glyphs
+ * for a particular font face.
+ *
+ * Individual synthesis features of a #cairo_ft_font_face_t can be set
+ * using cairo_ft_font_face_set_synthesize(), or disabled using
+ * cairo_ft_font_face_unset_synthesize(). The currently enabled set of
+ * synthesis options can be queried with cairo_ft_font_face_get_synthesize().
+ *
+ * Note: that when synthesizing glyphs, the font metrics returned will only
+ * be estimates.
+ *
+ * @CAIRO_FT_SYNTHESIZE_BOLD: Embolden the glyphs (redraw with a pixel offset)
+ * @CAIRO_FT_SYNTHESIZE_OBLIQUE: Slant the glyph outline by 12 degrees to the
+ * right.
+ *
+ * Since 1.12.
+ **/
+typedef enum {
+    CAIRO_FT_SYNTHESIZE_BOLD = 1 << 0,
+    CAIRO_FT_SYNTHESIZE_OBLIQUE = 1 << 1
+} cairo_ft_synthesize_t;
+
+cairo_public void
+cairo_ft_font_face_set_synthesize (cairo_font_face_t *font_face,
+				   unsigned int flags);
+
+cairo_public void
+cairo_ft_font_face_unset_synthesize (cairo_font_face_t *font_face,
+				     unsigned int flags);
+
+cairo_public unsigned int
+cairo_ft_font_face_get_synthesize (cairo_font_face_t *font_face);
+
+
 cairo_public FT_Face
 cairo_ft_scaled_font_lock_face (cairo_scaled_font_t *scaled_font);