fontselect: coretext: get fallback font family name via FreeType

Since commit be0d1613f79a95073d18d96a60e1394abf9316a2,
get_fallback can return a name from Core Text that is different
from all names that match_fonts registers for the same font.
This causes font fallback to fail as find_fonts fails to
find any font having the name received from get_fallback.
(Moreover, libass will keep retrying fallback for other glyphs,
and the coretext match_fonts will keep readding the same fonts
over and over again.)

Commit 152d0484e98f118d01987138695cf40579c9e297 attempted
to fix font fallback by getting a full name from Core Text
instead of a family name when it was noticed that Core Text's
family name can come from TT_NAME_ID_TYPOGRAPHIC_FAMILY
in addition to TT_NAME_ID_FONT_FAMILY, which we fetch in
get_font_info, but the problem goes deeper: Core Text can return
Macintosh-platform names that don't match Microsoft-platform
names, or the font might have no Microsoft-platform names at all.
Furthermore, returning a full name breaks style matching:
get_fallback does not know about weight, slant etc. and is
expected to return a whole family of fonts that will be
lazy-loaded in its entirety (if applicable) and searched
through for the best stylistic match by find_fonts.

To fix fallback while preserving maximum name portability
in the spirit of be0d1613f79a95073d18d96a60e1394abf9316a2,
use the same API in get_fallback as is used in match_fonts
to look up a family name.

Note: this could be more efficient if ass_get_font_info
could be told to return just an arbitrary family name.

This fixes https://github.com/libass/libass/issues/457.

1 files changed, 1 insertions, 1 deletions

diff --git a/libass/ass_fontselect.c b/libass/ass_fontselect.c
index 6b62511..3013f4a 100644
--- a/libass/ass_fontselect.c
+++ b/libass/ass_fontselect.c
@@ -717,7 +717,7 @@ char *ass_font_select(ASS_FontSelector *priv, ASS_Library *library,
         if (!search_family || !*search_family)
             search_family = "Arial";
         char *fallback_family = default_provider->funcs.get_fallback(
-                default_provider->priv, search_family, code);
+                default_provider->priv, library, search_family, code);
 
         if (fallback_family) {
             res = select_font(priv, library, fallback_family, bold, italic,