player/loadfile: rewrite sub autoselection logic

There's too many dumb options related to subtitles which have annoying
edge cases. Try to rewrite this completely so it hopefully behaves
normally in every expected scenario. A key goal here is be smarter while
looping through the tracks and avoid selecting the subtitle if it
doesn't meet user's passed options as opposed to clearing the pick after
the fact. Fixes #13280 and fixes #13263.

2 files changed, 29 insertions, 51 deletions

diff --git a/player/core.h b/player/core.h
index 9d9c4e8307..d995a88366 100644
--- a/player/core.h
+++ b/player/core.h
@@ -120,6 +120,7 @@ struct track {
     char *title;
     bool default_track, forced_track, dependent_track;
     bool visual_impaired_track, hearing_impaired_track;
+    bool forced_select; // if the track was selected because it is forced
     bool image;
     bool attached_picture;
     char *lang;
diff --git a/player/loadfile.c b/player/loadfile.c
index 4bd5a110aa..b8ccf6723e 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -483,9 +483,10 @@ static int match_lang(char **langs, const char *lang)
  * Forced tracks are preferred when the user prefers not to display subtitles
  */
 // Return whether t1 is preferred over t2
-static bool compare_track(struct track *t1, struct track *t2, char **langs,
-                          bool os_langs, struct MPOpts *opts, int preferred_program)
+static bool compare_track(struct track *t1, struct track *t2, char **langs, bool os_langs,
+                          bool forced, struct MPOpts *opts, int preferred_program)
 {
+    bool sub = t2->type == STREAM_SUB;
     if (!opts->autoload_files && t1->is_external != t2->is_external)
         return !t1->is_external;
     bool ext1 = t1->is_external && !t1->no_default;
@@ -503,16 +504,18 @@ static bool compare_track(struct track *t1, struct track *t2, char **langs,
             (t2->program_id == preferred_program))
             return t1->program_id == preferred_program;
     }
-    int forced = t1->type == STREAM_SUB ? opts->subs_fallback_forced : 1;
-    bool force_match = forced == 1 || (t1->forced_track && forced == 2) ||
-                       (!t1->forced_track && !forced);
     int l1 = match_lang(langs, t1->lang), l2 = match_lang(langs, t2->lang);
+    t1->forced_select = sub && forced && t1->forced_track;
     if (!os_langs && l1 != l2)
-        return l1 > l2 && force_match;
-    if (t1->default_track != t2->default_track)
-        return t1->default_track && force_match;
+        return l1 > l2;
+    if (forced)
+        return t1->forced_track;
+    if (sub && !t2->forced_select && t2->forced_track)
+        return !t1->forced_track;
+    if (t1->default_track != t2->default_track && !t2->forced_select)
+        return t1->default_track;
     if (os_langs && l1 != l2)
-        return l1 > l2 && force_match;
+        return l1 > l2;
     if (t1->attached_picture != t2->attached_picture)
         return !t1->attached_picture;
     if (t1->stream && t2->stream && opts->hls_bitrate >= 0 &&
@@ -624,11 +627,7 @@ struct track *select_default_track(struct MPContext *mpctx, int order,
     }
     const char *audio_lang = get_audio_lang(mpctx);
     bool sub = type == STREAM_SUB;
-    bool fallback_forced = sub && opts->subs_fallback_forced;
-    bool audio_matches = false;
-    bool sub_fallback = false;
     struct track *pick = NULL;
-    struct track *forced_pick = NULL;
     for (int n = 0; n < mpctx->num_tracks; n++) {
         struct track *track = mpctx->tracks[n];
         if (track->type != type)
@@ -643,48 +642,26 @@ struct track *select_default_track(struct MPContext *mpctx, int order,
             continue;
         if (duplicate_track(mpctx, order, type, track))
             continue;
-        if (!pick || compare_track(track, pick, langs, os_langs, mpctx->opts, preferred_program))
+        if (sub) {
+            // Subtitle specific auto-selecting crap.
+            bool audio_matches = mp_match_lang_single(audio_lang, track->lang);
+            bool forced = track->forced_track && (opts->subs_fallback_forced == 2 ||
+                          (audio_matches && opts->subs_fallback_forced == 1));
+            bool lang_match = !os_langs && match_lang(langs, track->lang) > 0;
+            bool subs_fallback = (track->is_external && !track->no_default) || opts->subs_fallback == 2 ||
+                                 (opts->subs_fallback == 1 && track->default_track);
+            bool subs_matching_audio = (!match_lang(langs, audio_lang) || opts->subs_with_matching_audio == 2 ||
+                                        (opts->subs_with_matching_audio == 1 && track->forced_track));
+            if (subs_matching_audio && ((!pick && (forced || lang_match || subs_fallback)) ||
+                (pick && compare_track(track, pick, langs, os_langs, forced, mpctx->opts, preferred_program))))
+            {
+                pick = track;
+            }
+        } else if (!pick || compare_track(track, pick, langs, os_langs, false, mpctx->opts, preferred_program)) {
             pick = track;
-
-        // Autoselecting forced sub tracks requires the following:
-        // 1. Matches the audio language or --subs-fallback-forced=always.
-        // 2. Matches the users list of preferred languages or none were specified (i.e. slang was not set).
-        // 3. A track *wasn't* already selected by slang previously or the track->lang matches pick->lang and isn't forced.
-        bool valid_forced_slang = (os_langs || (mp_match_lang_single(pick->lang, track->lang) && !pick->forced_track) ||
-                                   (match_lang(langs, track->lang) && !match_lang(langs, pick->lang)));
-        bool audio_lang_match = mp_match_lang_single(audio_lang, track->lang);
-        if (fallback_forced && track->forced_track && valid_forced_slang && audio_lang_match &&
-            (!forced_pick || compare_track(track, forced_pick, langs, os_langs, mpctx->opts, preferred_program)))
-        {
-            forced_pick = track;
         }
     }
 
-    // If we found a forced track, use that.
-    if (forced_pick)
-        pick = forced_pick;
-
-    // Clear out any picks for these special cases for subtitles
-    if (pick) {
-        audio_matches = mp_match_lang_single(pick->lang, audio_lang);
-        sub_fallback = (pick->is_external && !pick->no_default) || opts->subs_fallback == 2 ||
-                        (opts->subs_fallback == 1 && pick->default_track);
-    }
-    if (pick && !forced_pick && sub && (!match_lang(langs, pick->lang) || os_langs) && !sub_fallback)
-        pick = NULL;
-    // Handle this after matching langs and selecting a fallback.
-    if (pick && sub && ((!opts->subs_with_matching_audio && audio_matches) ||
-        (opts->subs_with_matching_audio == 1 && audio_matches && !forced_pick)))
-    {
-        pick = NULL;
-    }
-    // Handle edge cases if we picked a track that doesn't match the --subs-fallback-forced value
-    if (pick && sub && ((!pick->forced_track && opts->subs_fallback_forced == 2) ||
-        (pick->forced_track && !opts->subs_fallback_forced)))
-    {
-        pick = NULL;
-    }
-
     if (pick && pick->attached_picture && !mpctx->opts->audio_display)
         pick = NULL;
     if (pick && !opts->autoload_files && pick->is_external)