add support for multi monitor setups

yes, this patch is probably highly dubious as I honestly don't
have much clue about the wayland event loop. but hey, it seems
to work just fine

wayneko.c

@@ -12,6 +12,7 @@
 #include <sys/time.h>
 #include <time.h>
 #include <unistd.h>
+#include <wayland-client-protocol.h>
 #include <wayland-client.h>
 
 #ifdef __linux__
@@ -37,6 +38,7 @@ const char usage[] =
     "  --awake-phase       seconds-seconds\n"
     "  --currently         awake|asleep|random\n"
 	"  --layer             background|bottom|top|overlay\n"
+	"  --output            name\n"
 	"  --survive-close\n"
 	"\n";
 
@@ -101,6 +103,12 @@ uint32_t phase_awake_max = 600;
 
 bool wakeup_shock = false; /* will force a shock, used when woken up */
 
+char* output_name = NULL;
+struct wl_output* output = NULL;
+
+uint32_t required_hits = 1; /* we at least need the sync */
+uint32_t found_hits = 0;
+
 struct Seat
 {
 	struct wl_list link;
@@ -1204,7 +1212,7 @@ static void surface_create (void)
 	surface.layer_surface = zwlr_layer_shell_v1_get_layer_surface(
 		layer_shell,
 		surface.wl_surface,
-		NULL,
+		output,
 		layer,
 		"wayneko"
 	);
@@ -1233,11 +1241,33 @@ static void surface_create (void)
 	wl_surface_commit(surface.wl_surface);
 }
 
+static void attempt_surface_creation (void) {
+    // waits until we have seen all outputs
+    if (required_hits <= ++found_hits) surface_create();
+}
+
 /**********
  *        *
  *  Main  *
  *        *
  **********/
+static void handle_output_name(void *data, struct wl_output *wl_output, const char *name) {
+    if (strcmp(name, output_name) == 0) {
+        output = wl_output;
+    }
+
+    attempt_surface_creation();
+}
+
+static const struct wl_output_listener output_listener = {
+    .name = handle_output_name,
+    .geometry = noop,
+    .mode = noop,
+    .done = noop,
+    .scale = noop,
+    .description = noop
+};
+
 static void registry_handle_global (void *data, struct wl_registry *registry,
 		uint32_t name, const char *interface, uint32_t version)
 {
@@ -1249,10 +1279,14 @@ static void registry_handle_global (void *data, struct wl_registry *registry,
 		wl_shm = wl_registry_bind(registry, name, &wl_shm_interface, 1);
 	else if ( strcmp(interface, ext_idle_notifier_v1_interface.name) == 0 )
 		idle_notifier = wl_registry_bind(registry, name, &ext_idle_notifier_v1_interface, 1);
-	else if ( strcmp(interface, wl_seat_interface.name) == 0 )
-	{
+	else if ( strcmp(interface, wl_seat_interface.name) == 0 ) {
 		struct wl_seat *wl_seat = wl_registry_bind(registry, name, &wl_seat_interface, 7);
 		seat_new(wl_seat, name);
+	} else if ( strcmp(interface, wl_output_interface.name) == 0 && output_name != NULL) {
+	    struct wl_output* output = wl_registry_bind(registry, name, &wl_output_interface, version);
+
+		required_hits++; // we want to wait for this monitor to be checked before surface creation
+	    wl_output_add_listener(output, &output_listener, NULL);
 	}
 }
 
@@ -1308,7 +1342,7 @@ static void sync_handle_done (void *data, struct wl_callback *wl_callback, uint3
 		}
 	}
 
-	surface_create();
+	attempt_surface_creation();
 }
 
 static const struct wl_callback_listener sync_callback_listener = {
@@ -1531,6 +1565,14 @@ int main (int argc, char *argv[])
 			if (current_phase == PHASE_AWAKE)
 			    current_neko = NEKO_SLEEP_1;
 		}
+		else if ( strcmp(argv[i], "--output") == 0 )
+		{
+			char *t = get_argument(argc, argv, &i);
+			if ( t == NULL )
+				return EXIT_FAILURE;
+
+			output_name = t;
+		}
 		else
 		{
 			fprintf(stderr, "ERROR: Unknown option: %s\n", argv[i]);