Remove coretext_aat shaper (#1581)

coretext_aat was a temporary shaper to redirect shaping of AAT fonts
to CoreText and leaving the rest for HarfBuzz.  As HarfBuzz now supports
AAT and Chrome now actually ships that on a stable version on macOS,
we no longer care about such use-case.  If a client really wants 100%
metrics compatibility with CoreText better to use it directly or through
our API.  Replicating the same behavior still is possible using
hb_shape_full, something we don't care or like to offer anymore.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1478

src/hb-coretext.cc

@@ -1148,59 +1148,3 @@ fail:
 
   return ret;
 }
-
-
-/*
- * AAT shaper
- */
-
-/*
- * shaper face data
- */
-
-struct hb_coretext_aat_face_data_t {};
-
-hb_coretext_aat_face_data_t *
-_hb_coretext_aat_shaper_face_data_create (hb_face_t *face)
-{
-  return hb_aat_layout_has_substitution (face) || hb_aat_layout_has_positioning (face) ?
-	 (hb_coretext_aat_face_data_t *) HB_SHAPER_DATA_SUCCEEDED : nullptr;
-}
-
-void
-_hb_coretext_aat_shaper_face_data_destroy (hb_coretext_aat_face_data_t *data HB_UNUSED)
-{
-}
-
-
-/*
- * shaper font data
- */
-
-struct hb_coretext_aat_font_data_t {};
-
-hb_coretext_aat_font_data_t *
-_hb_coretext_aat_shaper_font_data_create (hb_font_t *font)
-{
-  return font->data.coretext ? (hb_coretext_aat_font_data_t *) HB_SHAPER_DATA_SUCCEEDED : nullptr;
-}
-
-void
-_hb_coretext_aat_shaper_font_data_destroy (hb_coretext_aat_font_data_t *data HB_UNUSED)
-{
-}
-
-
-/*
- * shaper
- */
-
-hb_bool_t
-_hb_coretext_aat_shape (hb_shape_plan_t    *shape_plan,
-			hb_font_t          *font,
-			hb_buffer_t        *buffer,
-			const hb_feature_t *features,
-			unsigned int        num_features)
-{
-  return _hb_coretext_shape (shape_plan, font, buffer, features, num_features);
-}

src/hb-shaper-list.hh

@@ -45,10 +45,6 @@ HB_SHAPER_IMPLEMENT (directwrite)
 #endif
 #ifdef HAVE_CORETEXT
 HB_SHAPER_IMPLEMENT (coretext)
-
-/* Only picks up fonts that have a "mort" or "morx" table.
-   Probably going to be removed https://github.com/harfbuzz/harfbuzz/issues/1478 */
-HB_SHAPER_IMPLEMENT (coretext_aat)
 #endif
 
 #ifdef HAVE_FALLBACK