playloop: only notify MP_EVENT_INPUT_PROCESSED when needed

MP_EVENT_INPUT_PROCESSED is used to notify mouse and touch position
updates, but it is currently notified for all input commands even when
they have nothing to do with mouse position. This results in unnecessary
acquisition and comparision of mouse and touch positions for all commands.

Optimize this by checking whether the command is marked as requiring the
event notification, and only notify if that is true.

player/playloop.c

@@ -108,16 +108,17 @@ void mp_core_unlock(struct MPContext *mpctx)
 // Process any queued user input.
 static void mp_process_input(struct MPContext *mpctx)
 {
-    int processed = 0;
+    bool notify = false;
     for (;;) {
         mp_cmd_t *cmd = mp_input_read_cmd(mpctx->input);
         if (!cmd)
             break;
+        if (cmd->notify_event)
+            notify = true;
         run_command(mpctx, cmd, NULL, NULL, NULL);
-        processed = 1;
     }
     mp_set_timeout(mpctx, mp_input_get_delay(mpctx->input));
-    if (processed)
+    if (notify)
         mp_notify(mpctx, MP_EVENT_INPUT_PROCESSED, NULL);
 }