command: add rescan_external_files

Requested.

Hopefully will be useful for things that download and add external
subtitles on demand. Or something.

Closes #1586.

DOCS/man/input.rst

@@ -400,6 +400,21 @@ List of Input Commands
 ``audio_reload [<id>]``
     Reload the given audio tracks. See ``sub_reload`` command.
 
+``rescan_external_files [<mode>]``
+    Rescan external files according to the current ``--sub-auto`` and
+    ``--audio-file-auto`` settings. This can be used to auto-load external
+    files *after* the file was loaded.
+
+    The ``mode`` argument is one of the following:
+
+    <keep-selection> (default)
+        Do not change current track selections.
+
+    <reselect>
+        Select the default audio and video streams, which typically selects
+        external files with highest preference. (The implementation is not
+        perfect, and could be improved on request.)
+
 
 Input Commands that are Possibly Subject to Change
 --------------------------------------------------

input/cmd_list.c

@@ -199,6 +199,11 @@ const struct mp_cmd_def mp_cmds[] = {
   { MP_CMD_AUDIO_REMOVE, "audio_remove", { OARG_INT(-1) } },
   { MP_CMD_AUDIO_RELOAD, "audio_reload", { OARG_INT(-1) } },
 
+  { MP_CMD_RESCAN_EXTERNAL_FILES, "rescan_external_files", {
+      OARG_CHOICE(0, ({"keep-selection", 0},
+                      {"reselect", 1})),
+  }},
+
   {0}
 };
 

input/cmd_list.h

@@ -111,6 +111,8 @@ enum mp_command_type {
     MP_CMD_HOOK_ADD,
     MP_CMD_HOOK_ACK,
 
+    MP_CMD_RESCAN_EXTERNAL_FILES,
+
     // Internal
     MP_CMD_COMMAND_LIST, // list of sub-commands in args[0].v.p
 };

player/command.c

@@ -4636,6 +4636,24 @@ int run_command(MPContext *mpctx, mp_cmd_t *cmd)
         return -1;
     }
 
+    case MP_CMD_RESCAN_EXTERNAL_FILES: {
+        if (!mpctx->playing)
+            return -1;
+        autoload_external_files(mpctx);
+        if (cmd->args[0].v.i) {
+            // somewhat fuzzy and not ideal
+            struct track *a = select_track(mpctx, STREAM_AUDIO, opts->audio_id,
+                                           opts->audio_id_ff, opts->audio_lang);
+            if (a && a->is_external)
+                mp_switch_track(mpctx, STREAM_AUDIO, a);
+            struct track *s = select_track(mpctx, STREAM_SUB, opts->sub_id,
+                                           opts->sub_id_ff, opts->sub_lang);
+            if (s && s->is_external)
+                mp_switch_track(mpctx, STREAM_SUB, s);
+        }
+        break;
+    }
+
     case MP_CMD_SCREENSHOT:
         screenshot_request(mpctx, cmd->args[0].v.i, cmd->args[1].v.i, msg_osd);
         break;

player/core.h

@@ -394,6 +394,9 @@ void mp_play_files(struct MPContext *mpctx);
 void update_demuxer_properties(struct MPContext *mpctx);
 void reselect_demux_streams(struct MPContext *mpctx);
 void prepare_playlist(struct MPContext *mpctx, struct playlist *pl);
+void autoload_external_files(struct MPContext *mpctx);
+struct track *select_track(struct MPContext *mpctx, enum stream_type type,
+                           int tid, int ffid, char **langs);
 
 // main.c
 int mpv_main(int argc, char *argv[]);

player/loadfile.c

@@ -441,9 +441,8 @@ static bool compare_track(struct track *t1, struct track *t2, char **langs,
     }
     return t1->user_tid <= t2->user_tid;
 }
-static struct track *select_track(struct MPContext *mpctx,
-                                  enum stream_type type, int tid, int ffid,
-                                  char **langs)
+struct track *select_track(struct MPContext *mpctx, enum stream_type type,
+                           int tid, int ffid, char **langs)
 {
     if (ffid != -1)
         tid = -1; // prefer selecting ffid
@@ -727,7 +726,7 @@ static void open_subtitles_from_options(struct MPContext *mpctx)
         mp_add_external_file(mpctx, opts->sub_name[i], STREAM_SUB);
 }
 
-static void autoload_external_files(struct MPContext *mpctx)
+void autoload_external_files(struct MPContext *mpctx)
 {
     if (mpctx->opts->sub_auto < 0 && mpctx->opts->audiofile_auto < 0)
         return;