From f4ac793e014740f24db7414a9c6374196f096ac5 Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Thu, 1 Oct 2026 14:50:44 +0100
Subject: [PATCH] vt_libseat: dispatch libseat events queued during open

seatd answers CLIENT_OPEN_SEAT by buffering the response and the enable
event together, so both reach libseat in one read and nothing is left on
the socket for the event loop to report. Watching the libseat fd for
readability therefore never activates the seat: seat_go_awake() is never
reached, no video device is initialised and nothing is drawn.

Dispatch libseat once from an idle callback, which runs after the loop
has started, as the real VT backend reports activation from. The seat is
also enabled while libseat_open_seat() is still running, before
uterm_vt_allocate() has installed the callbacks an activation needs, so
hold such an enable and replay it from the same callback.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 src/uterm/vt_libseat.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

--- a/src/uterm/vt_libseat.c
+++ b/src/uterm/vt_libseat.c
@@ -44,6 +44,7 @@ struct uterm_vt_libseat {
 
 	struct libseat *libseat;
 	struct ev_fd *libseat_efd;
+	bool enable_pending;
 	int tty_fd;
 	int tty_num;
 	int saved_kbmode;
@@ -135,6 +136,16 @@ static void vt_libseat_enable(struct lib
 	log_debug("libseat: seat enabled");
 
 	tty_activate(vt);
+
+	/*
+	 * seatd enables the seat while we are still opening it, which is before
+	 * uterm_vt_allocate() has installed the callbacks an activation needs.
+	 */
+	if (!vt->base.cb.activate) {
+		vt->enable_pending = true;
+		return;
+	}
+
 	vt_cb_activate(&vt->base);
 }
 
@@ -156,6 +167,25 @@ static void vt_libseat_event(struct ev_f
 		log_warning("libseat dispatch failed: %m");
 }
 
+/*
+ * seatd flushes the enable event together with the response to opening the
+ * seat, so it can already be buffered inside libseat with nothing left on the
+ * socket to make the eloop report our fd readable. Drain it once the loop is
+ * running, which is also where the real VT backend reports activation from.
+ */
+static void vt_libseat_idle(struct ev_eloop *eloop, void *unused, void *data)
+{
+	struct uterm_vt_libseat *vt = data;
+
+	if (libseat_dispatch(vt->libseat, 0) < 0)
+		log_warning("initial libseat dispatch failed: %m");
+
+	if (vt->enable_pending) {
+		vt->enable_pending = false;
+		vt_cb_activate(&vt->base);
+	}
+}
+
 static const struct libseat_seat_listener libseat_listener = {
 	.enable_seat = vt_libseat_enable,
 	.disable_seat = vt_libseat_disable,
@@ -166,6 +196,7 @@ static void vt_libseat_destroy(struct ut
 	struct uterm_vt_libseat *vt = to_libseat(base);
 
 	close_tty(vt);
+	ev_eloop_unregister_idle_cb(vt->base.eloop, vt_libseat_idle, vt, EV_ONESHOT);
 	ev_eloop_rm_fd(vt->libseat_efd);
 	libseat_close_seat(vt->libseat);
 }
@@ -379,6 +410,12 @@ struct uterm_vt *uterm_vt_libseat_new(st
 	if (ret)
 		goto err_libseat_fd;
 
+	ret = ev_eloop_register_idle_cb(vt->base.eloop, vt_libseat_idle, vt, EV_ONESHOT);
+	if (ret) {
+		log_error("cannot register libseat idle callback: %d", ret);
+		goto err_libseat_fd;
+	}
+
 	return &vt->base;
 
 err_libseat_fd: