seatd: deliver the enable event sent while opening a seat

seatd answers CLIENT_OPEN_SEAT by buffering the response and the enable
event together, so both reach libseat in one read. libseat parses only
the response and leaves the event in its connection buffer, with nothing
left on the socket for a client watching the fd to be woken by, so a
client that follows the documented contract never activates its seat.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

libs/seatd/Makefile

@@ -2,7 +2,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=seatd
 PKG_VERSION:=0.9.3
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.sr.ht/~kennylevinsen/seatd

libs/seatd/patches/100-libseat-drain-events-queued-while-opening.patch

@@ -0,0 +1,40 @@
+From 4c8c6046a8dba6dd5ab4b60a62cb5abe3aefa5d2 Mon Sep 17 00:00:00 2001
+From: Daniel Golle <daniel@makrotopia.org>
+Date: Thu, 1 Oct 2026 14:49:22 +0100
+Subject: [PATCH] libseat/seatd: drain events queued while opening the seat
+
+seatd answers CLIENT_OPEN_SEAT by buffering SERVER_SEAT_OPENED and then
+calling seat_open_client(), which buffers SERVER_ENABLE_SEAT, so both
+messages reach the client in a single read. read_and_queue() stops at
+the first non-event header, restores it and returns, which leaves the
+enable event unparsed in the connection buffer. _open_seat() consumes
+only the response and then calls execute_events() on an empty queue.
+
+Nothing is left on the socket at that point, so a client that dispatches
+when its fd becomes readable, as the documented contract invites, never
+sees the event and never activates its seat. Read and queue once more
+before executing, so an event delivered alongside the response is
+handled during open.
+
+Signed-off-by: Daniel Golle <daniel@makrotopia.org>
+---
+ libseat/backend/seatd.c | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+--- a/libseat/backend/seatd.c
++++ b/libseat/backend/seatd.c
+@@ -432,6 +432,14 @@ static struct libseat *_open_seat(const
+ 		goto backend_error;
+ 	}
+ 
++	// The server flushes the enable event together with the open response,
++	// so it is likely already sitting in our connection buffer with
++	// nothing left on the socket to wake a poll on our fd.
++	if (read_and_queue(backend, NULL) == -1) {
++		res = -errno;
++		goto backend_error;
++	}
++
+ 	execute_events(backend);
+ 	return &backend->base;
+