libass: match font attachments based on extension

Instead of only relying on the MIME type, use the file extension as a
fallback for deciding which attachments are fonts and should be fed to
libass.
This also refactors the check into a separate function in mpcommon.

mencoder.c

@@ -1060,10 +1060,7 @@ default: {
     if (ass_library) {
       for (i = 0; i < demuxer->num_attachments; ++i) {
         demux_attachment_t* att = demuxer->attachments + i;
-        if (use_embedded_fonts &&
+        if (use_embedded_fonts && attachment_is_font(att))
-            att->name && att->type && att->data && att->data_size &&
-            (strcmp(att->type, "application/x-truetype-font") == 0 ||
-             strcmp(att->type, "application/x-font") == 0))
           ass_add_font(ass_library, att->name, att->data, att->data_size);
       }
     }

mpcommon.c

@@ -297,6 +297,24 @@ int select_audio(demuxer_t* demuxer, int audio_id, char* audio_lang)
     return demuxer->audio->id;
 }
 
+bool attachment_is_font(struct demux_attachment *att)
+{
+    if (!att->name || !att->type || !att->data || !att->data_size)
+        return false;
+    // match against MIME types
+    if (strcmp(att->type, "application/x-truetype-font") == 0
+        || strcmp(att->type, "application/x-font") == 0)
+        return true;
+    // fallback: match against file extension
+    if (strlen(att->name) > 4) {
+        char *ext = att->name + strlen(att->name) - 4;
+        if (strcasecmp(ext, ".ttf") == 0 || strcasecmp(ext, ".ttc") == 0
+            || strcasecmp(ext, ".otf") == 0)
+            return true;
+    }
+    return false;
+}
+
 /* Parse -noconfig common to both programs */
 int disable_system_conf=0;
 int disable_user_conf=0;

mpcommon.h

@@ -35,6 +35,7 @@ void update_subtitles(struct MPContext *mpctx, struct MPOpts *opts,
 void update_teletext(sh_video_t *sh_video, demuxer_t *demuxer, int reset);
 int select_audio(demuxer_t* demuxer, int audio_id, char* audio_lang);
 void set_osd_subtitle(struct MPContext *mpctx, subtitle *subs);
+bool attachment_is_font(struct demux_attachment *att);
 
 extern int disable_system_conf;
 extern int disable_user_conf;

mplayer.c

@@ -3756,10 +3756,7 @@ if (opts->ass_enabled && ass_library) {
         struct demuxer *d = mpctx->sources[j].demuxer;
         for (int i = 0; i < d->num_attachments; i++) {
             struct demux_attachment *att = d->attachments + i;
-            if (use_embedded_fonts
+            if (use_embedded_fonts && attachment_is_font(att))
-                && att->name && att->type && att->data && att->data_size
-                && (strcmp(att->type, "application/x-truetype-font") == 0
-                    || strcmp(att->type, "application/x-font") == 0))
                 ass_add_font(ass_library, att->name, att->data, att->data_size);
         }
     }