From 95d303d2dccae7b7fcca7a5212ccf03bfdc0c6f7 Mon Sep 17 00:00:00 2001
From: "Anna (navi) Figueiredo Gomes" <navi@vlhl.dev>
Date: Mon, 3 Apr 2023 13:20:05 -0300
Subject: vt-switch

Signed-off-by: Anna (navi) Figueiredo Gomes <navi@vlhl.dev>
---
 libseat/backend/noop.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 103 insertions(+), 4 deletions(-)

diff --git a/libseat/backend/noop.c b/libseat/backend/noop.c
index 18f26c3..3b63616 100644
--- a/libseat/backend/noop.c
+++ b/libseat/backend/noop.c
@@ -5,11 +5,13 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include <signal.h>
 #include <sys/socket.h>
 #include <unistd.h>
 
 #include "backend.h"
 #include "log.h"
+#include "terminal.h"
 
 struct backend_noop {
 	struct libseat base;
@@ -18,10 +20,29 @@ struct backend_noop {
 
 	bool initial_setup;
 	int sockets[2];
+
 };
 
+static int vt;
+bool should_reenable;
+
 extern const struct seat_impl noop_impl;
 
+static int vt_toggle(int vt, bool enable) {
+	int ttyfd = terminal_open(vt);
+	if (ttyfd == -1) {
+		log_errorf("Could not open terminal to switch to VT %d: %s", vt, strerror(errno));
+		return -1;
+	}
+
+	terminal_set_process_switching(ttyfd, true);
+	terminal_set_keyboard(ttyfd, !enable);
+	terminal_set_graphics(ttyfd, enable);
+
+	close(ttyfd);
+	return 0;
+}
+
 static struct backend_noop *backend_noop_from_libseat_backend(struct libseat *base) {
 	assert(base->impl == &noop_impl);
 	return (struct backend_noop *)base;
@@ -33,6 +54,35 @@ static void destroy(struct backend_noop *backend) {
 	free(backend);
 }
 
+static void vt_acq(int signal) {
+	(void)signal;
+	int ttyfd = terminal_open(vt);
+	if (ttyfd == -1) {
+		log_errorf("Could not open terminal to switch to VT %d: %s", vt, strerror(errno));
+		return;
+	}
+
+	terminal_ack_acquire(ttyfd);
+
+	close(ttyfd);
+}
+
+static void vt_rel(int signal) {
+	(void)signal;
+	int ttyfd = terminal_open(vt);
+	if (ttyfd == -1) {
+		log_errorf("Could not open terminal to switch to VT %d: %s",
+				vt, strerror(errno));
+		return;
+	}
+
+	terminal_ack_release(ttyfd);
+
+	vt_toggle(vt, false);
+
+	close(ttyfd);
+}
+
 static int close_seat(struct libseat *base) {
 	struct backend_noop *backend = backend_noop_from_libseat_backend(base);
 	destroy(backend);
@@ -69,10 +119,21 @@ static int close_device(struct libseat *base, int device_id) {
 }
 
 static int switch_session(struct libseat *base, int s) {
-	(void)base;
-	(void)s;
-	log_errorf("No-op backend cannot switch to session %d", s);
-	return -1;
+	struct backend_noop *backend = backend_noop_from_libseat_backend(base);
+
+	int ttyfd = terminal_open(vt);
+	if (ttyfd == -1) {
+		log_errorf("Could not open terminal to switch to VT %d: %s", vt, strerror(errno));
+		return -1;
+	}
+
+	backend->seat_listener->disable_seat(&backend->base, backend->seat_listener_data);
+
+	int ret = terminal_switch_vt(ttyfd, s);
+	should_reenable = false;
+
+	close(ttyfd);
+	return ret;
 }
 
 static int get_fd(struct libseat *base) {
@@ -80,6 +141,10 @@ static int get_fd(struct libseat *base) {
 	return backend->sockets[0];
 }
 
+static void noop(int signal) {
+	log_debugf("Handling sig %d", signal);
+}
+
 static int dispatch_background(struct libseat *base, int timeout) {
 	struct backend_noop *backend = backend_noop_from_libseat_backend(base);
 
@@ -88,6 +153,12 @@ static int dispatch_background(struct libseat *base, int timeout) {
 		backend->seat_listener->enable_seat(&backend->base, backend->seat_listener_data);
 	}
 
+	if (should_reenable) {
+		backend->seat_listener->enable_seat(&backend->base, backend->seat_listener_data);
+		vt_toggle(vt, true);
+		should_reenable = false;
+	}
+
 	struct pollfd fd = {
 		.fd = backend->sockets[0],
 		.events = POLLIN,
@@ -115,10 +186,38 @@ static struct libseat *noop_open_seat(const struct libseat_seat_listener *listen
 		return NULL;
 	}
 
+	int _vt;
+	const char *vt_env = getenv("LIBSEAT_VT");
+	if (!vt_env || (_vt = atoi(vt_env)) == 0) {
+		log_error("LIBSEAT_VT must be set to the current VT for the noop backend");
+		free(backend);
+		return NULL;
+	}
+
+	vt = _vt;
+
+	vt_toggle(vt, true);
+
+	{
+		struct sigaction sa;
+		sa.sa_handler = vt_rel;
+		sigemptyset(&sa.sa_mask);
+		sa.sa_flags = 0;
+		sigaction(SIGUSR1, &sa, NULL);
+	}
+	{
+		struct sigaction sa;
+		sa.sa_handler = vt_acq;
+		sigemptyset(&sa.sa_mask);
+		sa.sa_flags = 0;
+		sigaction(SIGUSR2, &sa, NULL);
+	}
+
 	backend->initial_setup = true;
 	backend->seat_listener = listener;
 	backend->seat_listener_data = data;
 	backend->base.impl = &noop_impl;
+	should_reenable = false;
 
 	return &backend->base;
 }
-- 
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