Implement IPC binding event (keyboard)

This implements the IPC binding event for keyboard bindings.  It is
slightly different from the i3 implementation [1] since sway supports
more than one non-modifier key in a binding. Thus the json interface has
been changed from:

    {
      ...
      "symbol": "t",
      ...
    }

to:

    {
      ...
      "symbols": [ "t" ],
      ...
    }

[1] http://i3wm.org/docs/ipc.html#_binding_event

include/ipc-server.h

@@ -21,6 +21,10 @@ void ipc_event_mode(const char *mode);
  * the name of that modifier.
  */
 void ipc_event_modifier(uint32_t modifier, const char *state);
+/**
+ * Send IPC keyboard binding event.
+ */
+void ipc_event_binding_keyboard(struct sway_binding *sb);
 const char *swayc_type_string(enum swayc_types type);
 
 #endif

sway/handlers.c

@@ -347,11 +347,14 @@ static bool handle_bindsym(struct sway_binding *binding) {
 	}
 
 	if (match) {
+		struct sway_binding *binding_copy = sway_binding_dup(binding);
 		struct cmd_results *res = handle_command(binding->command);
 		if (res->status != CMD_SUCCESS) {
 			sway_log(L_ERROR, "Command '%s' failed: %s", res->input, res->error);
 		}
+		ipc_event_binding_keyboard(binding_copy);
 		free_cmd_results(res);
+		free_sway_binding(binding_copy);
 		return true;
 	}
 
@@ -362,11 +365,14 @@ static bool handle_bindsym_release(struct sway_binding *binding) {
 	if (binding->keys->length == 1) {
 		xkb_keysym_t *key = binding->keys->items[0];
 		if (check_released_key(*key)) {
+			struct sway_binding *binding_copy = sway_binding_dup(binding);
 			struct cmd_results *res = handle_command(binding->command);
 			if (res->status != CMD_SUCCESS) {
 				sway_log(L_ERROR, "Command '%s' failed: %s", res->input, res->error);
 			}
+			ipc_event_binding_keyboard(binding_copy);
 			free_cmd_results(res);
+			free_sway_binding(binding_copy);
 			return true;
 		}
 	}

sway/ipc-server.c

@@ -298,6 +298,8 @@ void ipc_client_handle_command(struct ipc_client *client) {
 				client->subscribed_events |= IPC_EVENT_MODE;
 			} else if (strcmp(event_type, "modifier") == 0) {
 				client->subscribed_events |= IPC_EVENT_MODIFIER;
+			} else if (strcmp(event_type, "binding") == 0) {
+				client->subscribed_events |= IPC_EVENT_BINDING;
 			} else {
 				ipc_send_reply(client, "{\"success\": false}", 18);
 				ipc_client_disconnect(client);
@@ -633,3 +635,48 @@ void ipc_event_modifier(uint32_t modifier, const char *state) {
 
 	json_object_put(obj); // free
 }
+
+static void ipc_event_binding(json_object *sb_obj) {
+	json_object *obj = json_object_new_object();
+	json_object_object_add(obj, "change", json_object_new_string("run"));
+	json_object_object_add(obj, "binding", sb_obj);
+
+	const char *json_string = json_object_to_json_string(obj);
+	ipc_send_event(json_string, IPC_EVENT_BINDING);
+
+	json_object_put(obj); // free
+}
+
+void ipc_event_binding_keyboard(struct sway_binding *sb) {
+	json_object *sb_obj = json_object_new_object();
+	json_object_object_add(sb_obj, "command", json_object_new_string(sb->command));
+
+	const char *names[10];
+
+	int len = get_modifier_names(names, sb->modifiers);
+	int i;
+	json_object *modifiers = json_object_new_array();
+	for (i = 0; i < len; ++i) {
+		json_object_array_add(modifiers, json_object_new_string(names[i]));
+	}
+
+	json_object_object_add(sb_obj, "event_state_mask", modifiers);
+
+	// TODO: implement bindcode
+	json_object_object_add(sb_obj, "input_code", json_object_new_int(0));
+
+	json_object *symbols = json_object_new_array();
+	uint32_t keysym;
+	char buffer[64];
+	for (i = 0; i < sb->keys->length; ++i) {
+		keysym = *(uint32_t *)sb->keys->items[i];
+		if (xkb_keysym_get_name(keysym, buffer, 64) > 0) {
+			json_object_array_add(symbols, json_object_new_string(buffer));
+		}
+	}
+
+	json_object_object_add(sb_obj, "symbols", symbols);
+	json_object_object_add(sb_obj, "input_type", json_object_new_string("keyboard"));
+
+	ipc_event_binding(sb_obj);
+}