command: make sub-add and audio-add commands async

Pretty trivial, since commands can be async now, and the common code
even provides convenience like running commands on a worker thread.

The only ugly thing is that mp_add_external_file() needs an extra flag
for locking. This is because there's still some code which calls this
synchronously from the main thread, and unlocking the core makes no
sense there.

DOCS/man/input.rst

@@ -909,6 +909,9 @@ The only exception is the current legacy behavior with screenshot commands,
 which will be fixed later. Using the ``async`` prefix makes them run the file
 saving code in a detached manner.
 
+Currently the following commands have different waiting characteristics with
+sync vs. async: sub-add, audio-add
+
 Input Sections
 --------------
 

player/command.c

@@ -5520,7 +5520,7 @@ static void cmd_track_add(void *p)
             return;
         }
     }
-    int first = mp_add_external_file(mpctx, cmd->args[0].v.s, type);
+    int first = mp_add_external_file(mpctx, cmd->args[0].v.s, type, true);
     if (first < 0) {
         cmd->success = false;
         return;
@@ -5584,7 +5584,7 @@ static void cmd_track_reload(void *p)
     if (t && t->is_external && t->external_filename) {
         char *filename = talloc_strdup(NULL, t->external_filename);
         mp_remove_track(mpctx, t);
-        nt_num = mp_add_external_file(mpctx, filename, type);
+        nt_num = mp_add_external_file(mpctx, filename, type, false);
         talloc_free(filename);
     }
 
@@ -6039,6 +6039,7 @@ const struct mp_cmd_def mp_cmds[] = {
             OARG_STRING(""), OARG_STRING(""),
         },
         .priv = &(const int){STREAM_SUB},
+        .spawn_thread = true,
     },
     { "sub-remove", cmd_track_remove, { OARG_INT(-1) },
         .priv = &(const int){STREAM_SUB}, },
@@ -6169,6 +6170,7 @@ const struct mp_cmd_def mp_cmds[] = {
             OARG_STRING(""), OARG_STRING(""),
         },
         .priv = &(const int){STREAM_AUDIO},
+        .spawn_thread = true,
     },
     { "audio-remove", cmd_track_remove, { OARG_INT(-1) },
         .priv = &(const int){STREAM_AUDIO}, },

player/core.h

@@ -488,7 +488,7 @@ struct playlist_entry *mp_check_playlist_resume(struct MPContext *mpctx,
 void mp_abort_playback_async(struct MPContext *mpctx);
 void uninit_player(struct MPContext *mpctx, unsigned int mask);
 int mp_add_external_file(struct MPContext *mpctx, char *filename,
-                         enum stream_type filter);
+                         enum stream_type filter, bool unlock);
 #define FLAG_MARK_SELECTION 1
 void mp_switch_track(struct MPContext *mpctx, enum stream_type type,
                      struct track *track, int flags);

player/loadfile.c

@@ -579,7 +579,7 @@ bool mp_remove_track(struct MPContext *mpctx, struct track *track)
 // Add the given file as additional track. The filter argument controls how or
 // if tracks are auto-selected at any point.
 int mp_add_external_file(struct MPContext *mpctx, char *filename,
-                         enum stream_type filter)
+                         enum stream_type filter, bool unlock)
 {
     struct MPOpts *opts = mpctx->opts;
     if (!filename)
@@ -600,11 +600,19 @@ int mp_add_external_file(struct MPContext *mpctx, char *filename,
         break;
     }
 
+    if (unlock)
+        mp_core_unlock(mpctx);
+
     struct demuxer *demuxer =
         demux_open_url(filename, &params, mpctx->playback_abort, mpctx->global);
+    if (demuxer)
+        enable_demux_thread(mpctx, demuxer);
+
+    if (unlock)
+        mp_core_lock(mpctx);
+
     if (!demuxer)
         goto err_out;
-    enable_demux_thread(mpctx, demuxer);
 
     if (opts->rebase_start_time)
         demux_set_ts_offset(demuxer, -demuxer->start_time);
@@ -619,7 +627,11 @@ int mp_add_external_file(struct MPContext *mpctx, char *filename,
     }
 
     if (!has_any) {
+        if (unlock)
+            mp_core_unlock(mpctx);
         free_demuxer_and_stream(demuxer);
+        if (unlock)
+            mp_core_lock(mpctx);
         char *tname = mp_tprintf(20, "%s ", stream_type_name(filter));
         if (filter == STREAM_TYPE_COUNT)
             tname = "";
@@ -652,7 +664,7 @@ static void open_external_files(struct MPContext *mpctx, char **files,
                                 enum stream_type filter)
 {
     for (int n = 0; files && files[n]; n++)
-        mp_add_external_file(mpctx, files[n], filter);
+        mp_add_external_file(mpctx, files[n], filter, false);
 }
 
 void autoload_external_files(struct MPContext *mpctx)
@@ -691,7 +703,7 @@ void autoload_external_files(struct MPContext *mpctx)
             goto skip;
         if (list[i].type == STREAM_AUDIO && !sc[STREAM_VIDEO])
             goto skip;
-        int first = mp_add_external_file(mpctx, filename, list[i].type);
+        int first = mp_add_external_file(mpctx, filename, list[i].type, false);
         if (first < 0)
             goto skip;