master ade1238bce: Try to restore the initial "daemon" frame when a display goes down

[Po Lu]

branch: master
commit ade1238bce1cf69ebce8809a2d73cb92db94b977
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Try to restore the initial "daemon" frame when a display goes down
    
    * src/xterm.c (x_try_restore_frame): New function.
    (x_connection_closed): Call it if selected_frame is nil.
---
 src/xterm.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/xterm.c b/src/xterm.c
index 1d0e69d32b..85367b78e3 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -23312,6 +23312,22 @@ x_trace_wire (Display *dpy)
 
 static char *error_msg;
 
+/* Try to find a frame in Vframe_list, and make it the selected frame.
+   `delete_frame' sometimes misses the initial frame for an unknown
+   reason when Emacs is running as a background daemon.  */
+
+static void
+x_try_restore_frame (void)
+{
+  Lisp_Object tail, frame;
+
+  FOR_EACH_FRAME (tail, frame)
+    {
+      if (!NILP (do_switch_frame (frame, 1, Qnil)))
+       return;
+    }
+}
+
 /* Handle the loss of connection to display DPY.  ERROR_MESSAGE is
    the text of an error message that lead to the connection loss.  */
 
@@ -23529,6 +23545,11 @@ For details, see etc/PROBLEMS.\n",
       Fdelete_terminal (tmp, Qnoelisp);
     }
 
+  /* The initial "daemon" frame is sometimes not selected by
+     `delete_frame' when Emacs is a background daemon.  */
+  if (NILP (selected_frame))
+    x_try_restore_frame ();
+
   unblock_input ();
 
   /* Sometimes another terminal is still alive, but deleting this