[pipe] Support for Shairport sync metadata flush event

src/inputs/pipe.c

@@ -370,6 +370,12 @@ handle_progress(struct input_metadata *m, char *progress)
   DPRINTF(E_DBG, L_PLAYER, "Received Shairport metadata progress: %" PRIi64 "/%" PRIi64 "/%" PRIi64 " => %d/%u ms\n", start, pos, end, m->pos_ms, m->len_ms);
 }
 
+static void
+handle_flush(void)
+{
+  player_playback_flush();
+}
+
 static void
 handle_volume(const char *volume)
 {
@@ -506,6 +512,12 @@ handle_item(struct input_metadata *m, const char *item)
       goto out_error;
     }
 
+  if (code == dmapval("pfls"))
+    {
+      handle_flush();
+      goto out_nothing;
+    }
+
   if (code == dmapval("asal"))
     dstptr = &m->album;
   else if (code == dmapval("asar"))

src/player.c

@@ -2463,6 +2463,33 @@ playback_pause(void *arg, int *retval)
   return COMMAND_END;
 }
 
+static enum command_state
+playback_flush(void *arg, int *retval)
+{
+  if (player_state == PLAY_STOPPED)
+    {
+      *retval = -1;
+      return COMMAND_END;
+    }
+
+  if (player_state == PLAY_PAUSED)
+    {
+      *retval = 0;
+      return COMMAND_END;
+    }
+
+  input_flush(NULL);
+
+  *retval = outputs_flush(device_flush_cb);
+  outputs_metadata_purge();
+
+  if (*retval > 0)
+    return COMMAND_PENDING; // async
+
+  // Otherwise we are done
+  return COMMAND_END;
+}
+
 static enum command_state
 playback_seek(void *arg, int *retval)
 {
@@ -2831,6 +2858,20 @@ speaker_authorize(void *arg, int *retval)
   return COMMAND_END;
 }
 
+static enum command_state
+speaker_start_all(void *arg, int *retval)
+{
+  outputs_stop_delayed_cancel();
+
+  *retval = outputs_start(device_activate_cb, device_shutdown_cb, false);
+
+  if (*retval > 0)
+    return COMMAND_PENDING; // async
+
+  // Otherwise we are done
+  return COMMAND_END;
+}
+
 static enum command_state
 volume_set(void *arg, int *retval)
 {
@@ -3161,6 +3202,27 @@ player_playback_pause(void)
   return ret;
 }
 
+/**
+ * Flushes outputs and input buffer, but does not stop the input read loop. Used
+ * by the pipe input when a track change is registered. Flushing outputs will
+ * stop them, so the command is two-step, i.e. it starts them again.
+ *
+ * @return Returns 0 on success and a negative value on error
+ */
+
+int
+player_playback_flush(void)
+{
+  int ret;
+
+  ret = commands_exec_sync(cmdbase, playback_flush, NULL, NULL);
+  if (ret < 0)
+    return ret;
+
+  ret = commands_exec_sync(cmdbase, speaker_start_all, NULL, NULL);
+  return ret;
+}
+
 /**
  * Seeks to the position "seek_ms", depending on the given "seek_mode" seek_ms is
  * either the new position in the current track (seek_mode == PLAYER_SEEK_POSITION)

src/player.h

@@ -132,6 +132,9 @@ player_playback_stop(void);
 int
 player_playback_pause(void);
 
+int
+player_playback_flush(void);
+
 int
 player_playback_seek(int seek_ms, enum player_seek_mode seek_mode);