Do not raise a pane when the mouse moves onto it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

regress/mouse-raise.sh

@@ -0,0 +1,70 @@
+#!/bin/sh
+
+# Moving the mouse onto a pane with focus-follows-mouse makes it active without
+# raising it.
+
+PATH=/bin:/usr/bin
+TERM=screen
+
+[ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
+
+cleanup()
+{
+	$TMUX kill-server >/dev/null 2>&1
+	$TMUX2 kill-server >/dev/null 2>&1
+}
+fail()
+{
+	echo "$*" >&2
+	cleanup
+	exit 1
+}
+
+# check PANE FORMAT EXPECTED
+check()
+{
+	got=$($TMUX display-message -p -t "$1" "$2")
+	[ "$got" = "$3" ] || fail "$1 $2: got '$got', expected '$3'"
+}
+
+# mouse SEQUENCE: send the escape sequence to the inner client.
+mouse()
+{
+	$TMUX2 send-keys -t "$OUTER" -l "$(printf "$1")" || fail "send-keys failed"
+	sleep 1
+}
+
+cleanup
+
+$TMUX new-session -d -s inner -x 80 -y 24 'sleep 100' || exit 1
+$TMUX set -g status off || exit 1
+$TMUX set -g mouse on || exit 1
+$TMUX set -g focus-follows-mouse on || exit 1
+$TMUX set -g pane-border-status top || exit 1
+A=$($TMUX display-message -p '#{pane_id}') || exit 1
+X=$($TMUX new-pane -dPF '#{pane_id}' -x 20 -y 6 -X 5 -Y 8 'sleep 100') || exit 1
+Y=$($TMUX new-pane -dPF '#{pane_id}' -x 20 -y 6 -X 45 -Y 8 'sleep 100') || exit 1
+
+$TMUX2 new-session -d -x 80 -y 24 "$TMUX attach -t inner" || exit 1
+sleep 1
+OUTER=$($TMUX2 list-panes -F '#{pane_id}' | head -1)
+[ -n "$OUTER" ] || fail "No outer pane."
+
+# Moving onto a floating pane that is behind another one focuses it but does not
+# raise it, whatever pane-raise-on-focus says.
+check "$A" '#{pane_active}' 1
+check "$Y" '#{pane_z}' 0
+mouse '\033[<35;12;12M\033[<35;14;13M'
+check "$X" '#{pane_active}' 1
+check "$Y" '#{pane_z}' 0
+
+# Clicking inside a pane still raises a floating pane, as before.
+mouse '\033[<0;54;12M\033[<0;54;12m'
+check "$Y" '#{pane_active}:#{pane_z}' '1:0'
+mouse '\033[<0;14;12M\033[<0;14;12m'
+check "$X" '#{pane_active}:#{pane_z}' '1:0'
+
+cleanup
+exit 0

server-client.c

@@ -1061,7 +1061,7 @@ have_event:
 		    wp != w->active &&
 		    options_get_number(s->options, "focus-follows-mouse")) {
 			window_redraw_active_switch(w, wp);
-			window_set_active_pane(w, wp, 1);
+			window_focus_pane(w, wp, 1);
 			server_redraw_window_borders(w);
 			server_status_window(w);
 		}

tmux.1

@@ -6060,6 +6060,11 @@ raises none.
 A floating or zoomed pane that is covered by a zoomed pane is always raised
 when it is made active; a tiled pane that is covered unzooms every pane
 instead.
+Moving the mouse onto a pane with
+.Ic focus\-follows\-mouse
+makes it active without raising it, so
+.Ic all
+is usually wanted with that option.
 .Pp
 .It Xo Ic pane\-scrollbars
 .Op Ic off | modal | on | auto\-hide

tmux.h

@@ -3708,6 +3708,7 @@ int		 window_has_pane(struct window *, struct window_pane *);
 int		 window_pane_contains(struct window_pane *, u_int, u_int);
 int		 window_pane_floating_overlaps(struct window_pane *,
 		     struct window_pane *);
+int		 window_focus_pane(struct window *, struct window_pane *, int);
 int		 window_set_active_pane(struct window *, struct window_pane *,
 		     int);
 void		 window_fire_pane_moved(struct window_pane *, struct window *,

window.c

@@ -73,6 +73,8 @@ static struct window_pane *window_pane_create(struct window *, u_int, u_int,
 static void	window_pane_destroy(struct window_pane *);
 static void	window_pane_free(struct window_pane *);
 static void	window_pane_scrollbar_timer(int, short, void *);
+static int	window_activate_pane(struct window *, struct window_pane *, int,
+		    int);
 static void	window_pane_full_size_offset(struct window_pane *, int *, int *,
 		    u_int *, u_int *);
 
@@ -742,6 +744,20 @@ window_pane_update_focus(struct window_pane *wp)
 
 int
 window_set_active_pane(struct window *w, struct window_pane *wp, int notify)
+{
+	return (window_activate_pane(w, wp, notify, 1));
+}
+
+/* Make a pane active without raising it, as when the mouse moves onto it. */
+int
+window_focus_pane(struct window *w, struct window_pane *wp, int notify)
+{
+	return (window_activate_pane(w, wp, notify, 0));
+}
+
+static int
+window_activate_pane(struct window *w, struct window_pane *wp, int notify,
+    int raise)
 {
 	struct window_pane *lastwp;
 
@@ -761,7 +777,7 @@ window_set_active_pane(struct window *w, struct window_pane *wp, int notify)
 			window_raise_pane(wp);
 		else
 			window_unzoom(w, 1);
-	} else {
+	} else if (raise) {
 		/* Raise the pane if the option says to. */
 		switch (options_get_number(w->options, "pane-raise-on-focus")) {
 		case PANE_RAISE_FLOATING: