swaymsg: add timeout and type checks

This adds a 3 second timeout to the initial reply in swaymsg. This
prevents swaymsg from hanging when `swaymsg -t get_{inputs,seats}` is
used in i3. The timeout is removed when waiting for a subscribed event
or monitoring for subscribed events.

This also adds type checks to commands where i3 does not reply with all
of the properties that sway does (such as `modes` in `get_outputs`).

This is mostly just a behavioral adjustment since swaymsg should run on
i3. When running under i3, some command reply's (such as the one for
`get_outputs) may have more useful information in the raw json than the
pretty printed version.

common/ipc-client.c

@@ -69,6 +69,16 @@ int ipc_open_socket(const char *socket_path) {
 	return socketfd;
 }
 
+bool ipc_set_recv_timeout(int socketfd, struct timeval tv) {
+	if (setsockopt(socketfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) == -1) {
+		sway_log_errno(SWAY_ERROR, "Failed to set ipc recv timeout");
+		return false;
+	}
+	sway_log(SWAY_DEBUG, "ipc recv timeout set to %ld.%06ld",
+			tv.tv_sec, tv.tv_usec);
+	return true;
+}
+
 struct ipc_response *ipc_recv_response(int socketfd) {
 	char data[IPC_HEADER_SIZE];
 	uint32_t *data32 = (uint32_t *)(data + sizeof(ipc_magic));

include/ipc-client.h

@@ -1,7 +1,9 @@
 #ifndef _SWAY_IPC_CLIENT_H
 #define _SWAY_IPC_CLIENT_H
 
+#include <stdbool.h>
 #include <stdint.h>
+#include <sys/time.h>
 
 #include "ipc.h"
 
@@ -36,5 +38,9 @@ struct ipc_response *ipc_recv_response(int socketfd);
  * Free ipc_response struct
  */
 void free_ipc_response(struct ipc_response *response);
+/**
+ * Sets the receive timeout for the IPC socket
+ */
+bool ipc_set_recv_timeout(int socketfd, struct timeval tv);
 
 #endif

swaymsg/main.c

@@ -7,6 +7,7 @@
 #include <stdint.h>
 #include <sys/un.h>
 #include <sys/socket.h>
+#include <sys/time.h>
 #include <ctype.h>
 #include <unistd.h>
 #include <json.h>
@@ -238,7 +239,8 @@ static void pretty_print_output(json_object *o) {
 		);
 	}
 
-	size_t modes_len = json_object_array_length(modes);
+	size_t modes_len = json_object_is_type(modes, json_type_array)
+		? json_object_array_length(modes) : 0;
 	if (modes_len > 0) {
 		printf("  Available modes:\n");
 		for (size_t i = 0; i < modes_len; ++i) {
@@ -448,6 +450,8 @@ int main(int argc, char **argv) {
 
 	int ret = 0;
 	int socketfd = ipc_open_socket(socket_path);
+	struct timeval timeout = {.tv_sec = 3, .tv_usec = 0};
+	ipc_set_recv_timeout(socketfd, timeout);
 	uint32_t len = strlen(command);
 	char *resp = ipc_single_command(socketfd, type, command, &len);
 	if (!quiet) {
@@ -478,6 +482,11 @@ int main(int argc, char **argv) {
 	free(resp);
 
 	if (type == IPC_SUBSCRIBE && ret == 0) {
+		// Remove the timeout for subscribed events
+		timeout.tv_sec = 0;
+		timeout.tv_usec = 0;
+		ipc_set_recv_timeout(socketfd, timeout);
+
 		do {
 			struct ipc_response *reply = ipc_recv_response(socketfd);
 			if (!reply) {