Show a message in locked frames in single-kboard mode

* src/keyboard.c (kbd_buffer_get_event): Pass the event's frame
up to the caller by means of a new 'struct frame **' argument.
(read_event_from_main_queue): Show a message in locked frames in
single-kboard mode (bug#79892).
* src/xdisp.c (log_message): Factor out of message3.
(message3): Call it.
(message3_nolog): Rename to ...
(message3_frame_nolog): ... this.  New 'struct frame *' argument
which causes temporarily switching to another frame when
displaying the message.
(message3_frame, message3_nolog): New functions.
* src/lisp.h: Declare message3_frame and message3_frame_nolog.
* admin/notes/multi-tty: Remove notes on showing a message.

1 files changed, 2 insertions, 16 deletions

diff --git a/admin/notes/multi-tty b/admin/notes/multi-tty
index 7783eb395e7..fff20a1769b 100644
--- a/admin/notes/multi-tty
+++ b/admin/notes/multi-tty
@@ -402,29 +402,15 @@ THINGS TO DO
 
 ** The single-keyboard mode of MULTI_KBOARD is extremely confusing
    sometimes; Emacs does not respond to stimuli from other keyboards.
-   At least a beep or a message would be important, if the single-mode
-   is still required to prevent interference.  (Reported by Dan
-   Nicolaescu.)
+   (Reported by Dan Nicolaescu.)
 
    Update: selecting a region with the mouse enables single_kboard
    under X.  This is very confusing.
 
    Update: After discussions with Richard Stallman, this will be
-   resolved by having locked displays warn the user to wait, and
-   introducing a complex protocol to remotely bail out of
+   resolved introducing a complex protocol to remotely bail out of
    single-kboard mode by pressing C-g.
 
-   Update: Warning the user is not trivial to implement, as Emacs has
-   only one echo area, shared by all frames.  Ideally the warning
-   should not be displayed on the display that is locking the others.
-   Perhaps the high probability of user confusion caused by
-   single_kboard mode deserves a special case in the display code.
-   Alternatively, it might be good enough to signal single_kboard mode
-   by changing the modelines or some other frame-local display element
-   on the locked out displays.
-
-   Update: In fact struct kboard does have an echo_string slot.
-
 ** The session management module is prone to crashes when the X
    connection is closed and then later I try to connect to a new X
    session: