Preserve tty top-frames under various window-changing operations.

* subr.el (with-selected-window): Preserve the selected window's
terminal's top-frame.

* window.el (save-selected-window): Likewise.

* frame.c (delete_frame): When selecting a frame on a different
text terminal, do not alter the terminal's top-frame.

* term.c (Ftty_top_frame): New function.

* xdisp.c (format_mode_line_unwind_data): Record the target
frame's selected window and its terminal's top-frame.
(unwind_format_mode_line): Restore them.
(x_consider_frame_title, display_mode_line, Fformat_mode_line):
Callers changed.
(x_consider_frame_title): Do not condition on HAVE_WINDOW_SYSTEM,
since tty frames can be explicitly named.
(prepare_menu_bars): Likewise.

Fixes: debbugs:4702

1 files changed, 2 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 629743bac4e..a2f3b95fe41 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -473,6 +473,8 @@ is detected.
 Emacs now supports mouse highlight, help-echo (in the echo area), and
 mouse-autoselect-window.
 
+** New function `tty-top-frame' returns the topmost frame of a text terminal.
+
 
 * Installation Changes in Emacs 24.1