Fix bug #13864 with flickering of TTY frames in an emacslient session.

 src/frame.c (do_switch_frame): Mark the TTY frame we switch to as
 garbaged only if it is not already the top frame on its TTY.  This
 prevents flickering due to constant redrawing of TTY frames when
 there are GUI frames open in the same session.

1 files changed, 12 insertions, 4 deletions

diff --git a/src/frame.c b/src/frame.c
index 2fe398296ed..ccd50122f50 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -834,10 +834,18 @@ do_switch_frame (Lisp_Object frame, int track, int for_deletion, Lisp_Object nor
 
   if (FRAME_TERMCAP_P (XFRAME (frame)) || FRAME_MSDOS_P (XFRAME (frame)))
     {
-      if (FRAMEP (FRAME_TTY (XFRAME (frame))->top_frame))
-        /* Mark previously displayed frame as now obscured.  */
-        SET_FRAME_VISIBLE (XFRAME (FRAME_TTY (XFRAME (frame))->top_frame), 2);
-      SET_FRAME_VISIBLE (XFRAME (frame), 1);
+      Lisp_Object top_frame = FRAME_TTY (XFRAME (frame))->top_frame;
+
+      /* Don't mark the frame garbaged and/or obscured if we are
+         switching to the frame that is already the top frame of that
+         TTY.  */
+      if (!EQ (frame, top_frame))
+        {
+          if (FRAMEP (top_frame))
+            /* Mark previously displayed frame as now obscured.  */
+            SET_FRAME_VISIBLE (XFRAME (top_frame), 2);
+          SET_FRAME_VISIBLE (XFRAME (frame), 1);
+        }
       FRAME_TTY (XFRAME (frame))->top_frame = frame;
     }