Spawn swaynag as a wayland client

This spawns swaynag as a wayland client similar to how swaybar and
swaybg are already done

sway/swaynag.c

@@ -1,16 +1,32 @@
 #define _POSIX_C_SOURCE 200809L
-#include <fcntl.h>
 #include <signal.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <sys/socket.h>
 #include <sys/types.h>
+#include <sys/wait.h>
 #include <unistd.h>
 #include "log.h"
+#include "sway/server.h"
 #include "sway/swaynag.h"
+#include "util.h"
+
+static void handle_swaynag_client_destroy(struct wl_listener *listener,
+		void *data) {
+	struct swaynag_instance *swaynag =
+		wl_container_of(listener, swaynag, client_destroy);
+	wl_list_remove(&swaynag->client_destroy.link);
+	wl_list_init(&swaynag->client_destroy.link);
+	swaynag->client = NULL;
+}
 
 bool swaynag_spawn(const char *swaynag_command,
 		struct swaynag_instance *swaynag) {
+	if (swaynag->client != NULL) {
+		wl_client_destroy(swaynag->client);
+	}
+
 	if (!swaynag_command) {
 		return true;
 	}
@@ -20,44 +36,94 @@ bool swaynag_spawn(const char *swaynag_command,
 			sway_log(SWAY_ERROR, "Failed to create pipe for swaynag");
 			return false;
 		}
-		fcntl(swaynag->fd[1], F_SETFD, FD_CLOEXEC);
+		if (!set_cloexec(swaynag->fd[1], true)) {
+			goto failed;
+		}
 	}
 
-	pid_t pid;
-	if ((pid = fork()) == 0) {
-		if (swaynag->detailed) {
-			close(swaynag->fd[1]);
-			dup2(swaynag->fd[0], STDIN_FILENO);
-			close(swaynag->fd[0]);
-		}
+	int sockets[2];
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) != 0) {
+		sway_log_errno(SWAY_ERROR, "socketpair failed");
+		goto failed;
+	}
+	if (!set_cloexec(sockets[0], true) || !set_cloexec(sockets[1], true)) {
+		goto failed;
+	}
 
-		size_t length = strlen(swaynag_command) + strlen(swaynag->args) + 2;
-		char *cmd = malloc(length);
-		snprintf(cmd, length, "%s %s", swaynag_command, swaynag->args);
-		execl("/bin/sh", "/bin/sh", "-c", cmd, NULL);
-		_exit(0);
-	} else if (pid < 0) {
+	swaynag->client = wl_client_create(server.wl_display, sockets[0]);
+	if (swaynag->client == NULL) {
+		sway_log_errno(SWAY_ERROR, "wl_client_create failed");
+		goto failed;
+	}
+
+	swaynag->client_destroy.notify = handle_swaynag_client_destroy;
+	wl_client_add_destroy_listener(swaynag->client, &swaynag->client_destroy);
+
+	pid_t pid = fork();
+	if (pid < 0) {
 		sway_log(SWAY_ERROR, "Failed to create fork for swaynag");
-		if (swaynag->detailed) {
-			close(swaynag->fd[0]);
-			close(swaynag->fd[1]);
+		goto failed;
+	} else if (pid == 0) {
+		pid = fork();
+		if (pid < 0) {
+			sway_log_errno(SWAY_ERROR, "fork failed");
+			_exit(EXIT_FAILURE);
+		} else if (pid == 0) {
+			if (!set_cloexec(sockets[1], false)) {
+				_exit(EXIT_FAILURE);
+			}
+
+			if (swaynag->detailed) {
+				close(swaynag->fd[1]);
+				dup2(swaynag->fd[0], STDIN_FILENO);
+				close(swaynag->fd[0]);
+			}
+
+			char wayland_socket_str[16];
+			snprintf(wayland_socket_str, sizeof(wayland_socket_str),
+					"%d", sockets[1]);
+			setenv("WAYLAND_SOCKET", wayland_socket_str, true);
+
+			size_t length = strlen(swaynag_command) + strlen(swaynag->args) + 2;
+			char *cmd = malloc(length);
+			snprintf(cmd, length, "%s %s", swaynag_command, swaynag->args);
+			execl("/bin/sh", "/bin/sh", "-c", cmd, NULL);
+			sway_log_errno(SWAY_ERROR, "execl failed");
+			_exit(EXIT_FAILURE);
 		}
-		return false;
+		_exit(EXIT_SUCCESS);
 	}
 
 	if (swaynag->detailed) {
-		close(swaynag->fd[0]);
+		if (close(swaynag->fd[0]) != 0) {
+			sway_log_errno(SWAY_ERROR, "close failed");
+			return false;
+		}
 	}
-	swaynag->pid = pid;
+
+	if (close(sockets[1]) != 0) {
+		sway_log_errno(SWAY_ERROR, "close failed");
+		return false;
+	}
+
+	if (waitpid(pid, NULL, 0) < 0) {
+		sway_log_errno(SWAY_ERROR, "waitpid failed");
+		return false;
+	}
+
 	return true;
-}
 
-
-void swaynag_kill(struct swaynag_instance *swaynag) {
-	if (swaynag->pid > 0) {
-		kill(swaynag->pid, SIGTERM);
-		swaynag->pid = -1;
+failed:
+	if (swaynag->detailed) {
+		if (close(swaynag->fd[0]) != 0) {
+			sway_log_errno(SWAY_ERROR, "close failed");
+			return false;
+		}
+		if (close(swaynag->fd[1]) != 0) {
+			sway_log_errno(SWAY_ERROR, "close failed");
+		}
 	}
+	return false;
 }
 
 void swaynag_log(const char *swaynag_command, struct swaynag_instance *swaynag,
@@ -71,7 +137,7 @@ void swaynag_log(const char *swaynag_command, struct swaynag_instance *swaynag,
 		return;
 	}
 
-	if (swaynag->pid <= 0 && !swaynag_spawn(swaynag_command, swaynag)) {
+	if (swaynag->client == NULL && !swaynag_spawn(swaynag_command, swaynag)) {
 		return;
 	}
 
@@ -96,7 +162,7 @@ void swaynag_log(const char *swaynag_command, struct swaynag_instance *swaynag,
 }
 
 void swaynag_show(struct swaynag_instance *swaynag) {
-	if (swaynag->detailed && swaynag->pid > 0) {
+	if (swaynag->detailed && swaynag->client != NULL) {
 		close(swaynag->fd[1]);
 	}
 }