[hb-style] Fix synthetic slant values

When reporting the slant ratio of a font
that has synthetic slant set, we were
reporting twice the expected value.
Fix that. Test included.

src/hb-style.cc

@@ -72,8 +72,7 @@ float
 hb_style_get_value (hb_font_t *font, hb_style_tag_t style_tag)
 {
   if (unlikely (style_tag == HB_STYLE_TAG_SLANT_RATIO))
-    return _hb_angle_to_ratio (hb_style_get_value (font, HB_STYLE_TAG_SLANT_ANGLE))
-	 + font->slant;
+    return _hb_angle_to_ratio (hb_style_get_value (font, HB_STYLE_TAG_SLANT_ANGLE));
 
   hb_face_t *face = font->face;
 

test/api/test-style.c

@@ -147,6 +147,22 @@ test_face_user_setting (void)
   hb_face_destroy (face);
 }
 
+static void
+test_synthetic_slant (void)
+{
+  hb_face_t *face = hb_test_open_font_file ("fonts/AdobeVFPrototype_vsindex.otf");
+  hb_font_t *font = hb_font_create (face);
+
+  assert_cmpfloat (hb_style_get_value (font, HB_STYLE_TAG_SLANT_RATIO), 0);
+
+  hb_font_set_synthetic_slant (font, 0.2);
+
+  assert_cmpfloat (hb_style_get_value (font, HB_STYLE_TAG_SLANT_RATIO), 0.2);
+
+  hb_font_destroy (font);
+  hb_face_destroy (face);
+}
+
 int
 main (int argc, char **argv)
 {
@@ -155,6 +171,7 @@ main (int argc, char **argv)
   hb_test_add (test_empty_face);
   hb_test_add (test_regular_face);
   hb_test_add (test_face_user_setting);
+  hb_test_add (test_synthetic_slant);
 
   return hb_test_run ();
 }