ipc: add `floating` property to GET_TREE

i3 has had this property for over a decade but it wasn't documented
until a couple of years ago, so it was likely missed when developing
sway. Add the property to get us closer to ipc parity with i3.

sway/ipc-json.c

@@ -288,6 +288,7 @@ static json_object *ipc_json_create_node(int id, const char* type, char *name,
 	json_object_object_add(object, "focus", focus);
 	json_object_object_add(object, "fullscreen_mode", json_object_new_int(0));
 	json_object_object_add(object, "sticky", json_object_new_boolean(false));
+	json_object_object_add(object, "floating", NULL);
 
 	return object;
 }
@@ -675,7 +676,8 @@ static void ipc_json_describe_view(struct sway_container *c, json_object *object
 static void ipc_json_describe_container(struct sway_container *c, json_object *object) {
 	json_object_object_add(object, "name",
 			c->title ? json_object_new_string(c->title) : NULL);
-	if (container_is_floating(c)) {
+	bool floating = container_is_floating(c);
+	if (floating) {
 		json_object_object_add(object, "type",
 				json_object_new_string("floating_con"));
 	}
@@ -693,6 +695,10 @@ static void ipc_json_describe_container(struct sway_container *c, json_object *o
 	json_object_object_add(object, "urgent", json_object_new_boolean(urgent));
 	json_object_object_add(object, "sticky", json_object_new_boolean(c->is_sticky));
 
+	// sway doesn't track the floating reason, so we can't use "auto_on" or "user_off"
+	json_object_object_add(object, "floating",
+			json_object_new_string(floating ? "user_on" : "auto_off"));
+
 	json_object_object_add(object, "fullscreen_mode",
 			json_object_new_int(c->pending.fullscreen_mode));
 

sway/sway-ipc.7.scd

@@ -376,6 +376,9 @@ node and will have the following properties:
 :  integer
 :  (Only containers and views) The fullscreen mode of the node. 0 means none, 1 means
    full workspace, and 2 means global fullscreen
+|- floating
+:  string
+:  Floating state of container. Can be either "auto_off" or "user_on"
 |- app_id
 :  string
 :  (Only views) For an xdg-shell view, the name of the application, if set.