player: loop on end of file if ab-loop-b is unset

Possibly slightly more useful/intuitive.

DOCS/interface-changes.rst

@@ -19,6 +19,9 @@ Interface changes
 
 ::
 
+ --- mpv 0.17.1 ---
+    - now ab-loops are active even if the "ab-loop-b" property is unset ("no"),
+      in which case the end of the file is used as B loop point
  --- mpv 0.17.0 ---
     - deprecate "track-list/N/audio-channels" property (use
       "track-list/N/demux-channel-count" instead)

DOCS/man/input.rst

@@ -1081,8 +1081,9 @@ Property list
                 "default"           MPV_FORMAT_FLAG
 
 ``ab-loop-a``, ``ab-loop-b`` (RW)
-    Set/get A-B loop points. See corresponding options and ``ab_loop`` command.
-    The special value ``no`` on either of these properties disables looping.
+    Set/get A-B loop points. See corresponding options and ``ab-loop`` command.
+    The special value ``no`` on ``ab-loop-a`` disables looping, while setting
+    ``ab-loop-b`` to ``no`` loops when the end of the file is reached.
 
 ``angle`` (RW)
     Current DVD angle.

player/command.c

@@ -5245,12 +5245,13 @@ void handle_ab_loop(struct MPContext *mpctx)
     struct MPOpts *opts = mpctx->opts;
 
     double now = mpctx->restart_complete ? mpctx->playback_pts : MP_NOPTS_VALUE;
-    if (now != MP_NOPTS_VALUE && opts->ab_loop[0] != MP_NOPTS_VALUE &&
-        opts->ab_loop[1] != MP_NOPTS_VALUE)
-    {
+    if (now != MP_NOPTS_VALUE && opts->ab_loop[0] != MP_NOPTS_VALUE) {
+        double end = opts->ab_loop[1];
+        if (end == MP_NOPTS_VALUE)
+            end = INFINITY;
         if (ctx->prev_pts >= opts->ab_loop[0] &&
-            ctx->prev_pts < opts->ab_loop[1] &&
-            (now >= opts->ab_loop[1] || mpctx->stop_play == AT_END_OF_FILE))
+            ctx->prev_pts < end &&
+            (now >= end || mpctx->stop_play == AT_END_OF_FILE))
         {
             mark_seek(mpctx);
             queue_seek(mpctx, MPSEEK_ABSOLUTE, opts->ab_loop[0],

player/playloop.c

@@ -978,6 +978,9 @@ void run_playloop(struct MPContext *mpctx)
 
     handle_sstep(mpctx);
 
+    if (mpctx->stop_play == AT_END_OF_FILE && mpctx->seek.type)
+        mpctx->stop_play = KEEP_PLAYING;
+
     if (mpctx->stop_play)
         return;