Add new event loop api for watching signals

This will provide us with a nice, safe mechanism
for getting notification of VT changes.

event-loop.c

@@ -23,11 +23,13 @@
 #include <stddef.h>
 #include <stdio.h>
 #include <errno.h>
+#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <sys/epoll.h>
+#include <sys/signalfd.h>
 #include <sys/timerfd.h>
 #include <unistd.h>
 #include <assert.h>
@@ -238,6 +240,87 @@ wl_event_source_timer_update(struct wl_event_source *source, int ms_delay)
 	return 0;
 }
 
+struct wl_event_source_signal {
+	struct wl_event_source base;
+	int fd;
+	int signal_number;
+	wl_event_loop_signal_func_t func;
+	void *data;
+};
+
+static void
+wl_event_source_signal_dispatch(struct wl_event_source *source,
+			       struct epoll_event *ep)
+{
+	struct wl_event_source_signal *signal_source =
+		(struct wl_event_source_signal *) source;
+	struct signalfd_siginfo signal_info;
+
+	read(signal_source->fd, &signal_info, sizeof signal_info);
+
+	signal_source->func(signal_source->signal_number, signal_source->data);
+}
+
+static int
+wl_event_source_signal_remove(struct wl_event_source *source)
+{
+	struct wl_event_source_signal *signal_source =
+		(struct wl_event_source_signal *) source;
+	struct wl_event_loop *loop = source->loop;
+	int fd;
+
+	fd = signal_source->fd;
+	free(source);
+
+	return epoll_ctl(loop->epoll_fd, EPOLL_CTL_DEL, fd, NULL);
+}
+
+struct wl_event_source_interface signal_source_interface = {
+	wl_event_source_signal_dispatch,
+	wl_event_source_signal_remove
+};
+
+WL_EXPORT struct wl_event_source *
+wl_event_loop_add_signal(struct wl_event_loop *loop,
+			int signal_number,
+			wl_event_loop_signal_func_t func,
+			void *data)
+{
+	struct wl_event_source_signal *source;
+	struct epoll_event ep;
+	sigset_t mask;
+
+	source = malloc(sizeof *source);
+	if (source == NULL)
+		return NULL;
+
+	source->base.interface = &signal_source_interface;
+	source->base.loop = loop;
+
+	sigemptyset(&mask);
+	sigaddset(&mask, signal_number);
+	source->fd = signalfd(-1, &mask, 0);
+	if (source->fd < 0) {
+		fprintf(stderr, "could not create fd to watch signal\n: %m");
+		free(source);
+		return NULL;
+	}
+	sigprocmask(SIG_BLOCK, &mask, NULL);
+
+	source->func = func;
+	source->data = data;
+
+	ep.events = EPOLLIN;
+	ep.data.ptr = source;
+
+	if (epoll_ctl(loop->epoll_fd, EPOLL_CTL_ADD, source->fd, &ep) < 0) {
+		free(source);
+		return NULL;
+	}
+
+	return &source->base;
+}
+
 struct wl_event_source_idle {
 	struct wl_event_source base;
 	struct wl_list link;

wayland.h

@@ -35,6 +35,7 @@ struct wl_event_loop;
 struct wl_event_source;
 typedef void (*wl_event_loop_fd_func_t)(int fd, uint32_t mask, void *data);
 typedef void (*wl_event_loop_timer_func_t)(void *data);
+typedef void (*wl_event_loop_signal_func_t)(int signal_number, void *data);
 typedef void (*wl_event_loop_idle_func_t)(void *data);
 
 struct wl_event_loop *wl_event_loop_create(void);
@@ -47,6 +48,12 @@ int wl_event_source_fd_update(struct wl_event_source *source, uint32_t mask);
 struct wl_event_source *wl_event_loop_add_timer(struct wl_event_loop *loop,
 						wl_event_loop_timer_func_t func,
 						void *data);
+struct wl_event_source *
+wl_event_loop_add_signal(struct wl_event_loop *loop,
+			int signal_number,
+			wl_event_loop_signal_func_t func,
+			void *data);
+
 int wl_event_source_timer_update(struct wl_event_source *source,
 				 int ms_delay);
 int wl_event_source_remove(struct wl_event_source *source);