Fix setting a tty's top frame when switching frames

* src/frame.c (do_switch_frame): Compare root frames correctly.

1 files changed, 9 insertions, 5 deletions

diff --git a/src/frame.c b/src/frame.c
index c4afbe6bbb6..258bf08788f 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1773,15 +1773,19 @@ do_switch_frame (Lisp_Object frame, int track, int for_deletion, Lisp_Object nor
       struct tty_display_info *tty = FRAME_TTY (f);
       Lisp_Object top_frame = tty->top_frame;
 
-      /* Don't mark the frame garbaged if we are switching to the frame
-         that is already the top frame of that TTY.  */
-      if (!EQ (frame, top_frame) && root_frame (f) != XFRAME (top_frame))
+      /* Switching to a frame on a different root frame is special.  The
+         old root frame has to be marked invisible, and the new root
+         frame has to be made visible.  */
+      if (!EQ (frame, top_frame)
+          && (!FRAMEP (top_frame)
+              || root_frame (f) != root_frame (XFRAME (top_frame))))
         {
           struct frame *new_root = root_frame (f);
           SET_FRAME_VISIBLE (new_root, true);
           SET_FRAME_VISIBLE (f, true);
 
-          /* Mark previously displayed frame as no longer visible.  */
+          /* Mark previously displayed root frame as no longer
+             visible.  */
           if (FRAMEP (top_frame))
             {
               struct frame *top = XFRAME (top_frame);
@@ -1792,7 +1796,7 @@ do_switch_frame (Lisp_Object frame, int track, int for_deletion, Lisp_Object nor
 
           tty->top_frame = frame;
 
-          /* FIXME: Why is it correct to set FrameCols/Rows?  */
+          /* FIXME: Why is it correct to set FrameCols/Rows here?  */
           if (!FRAME_PARENT_FRAME (f))
             {
               /* If the new TTY frame changed dimensions, we need to