commit https://github.com/vim/vim/commit/86edef664efccbfe685906c854b9cdd04e56f2d5 Author: Bram Moolenaar <Bram@vim.org> Date: Sun Mar 13 18:07:30 2016 +0100 patch 7.4.1557 Problem: Windows cannot be identified. Solution: Add a unique window number to each window and functions to use it.

--- a/src/structs.h
+++ b/src/structs.h
@@ -2273,6 +2273,8 @@ struct matchitem
  */
 struct window_S
 {
+    int		w_id;		    /* unique window ID */
+
     buf_T	*w_buffer;	    /* buffer we are a window into (used
 				       often, keep it the first item!) */