ipc: add xkb_layout_names and xkb_active_layout_index

These can be useful to implement per-window layouts as a script.

See https://github.com/swaywm/sway/issues/2361

sway/ipc-json.c

@@ -824,19 +824,24 @@ json_object *ipc_json_describe_input(struct sway_input_device *device) {
 		struct wlr_keyboard *keyboard = device->wlr_device->keyboard;
 		struct xkb_keymap *keymap = keyboard->keymap;
 		struct xkb_state *state = keyboard->xkb_state;
+
+		json_object *layouts_arr = json_object_new_array();
+		json_object_object_add(object, "xkb_layout_names", layouts_arr);
+
 		xkb_layout_index_t num_layouts = xkb_keymap_num_layouts(keymap);
 		xkb_layout_index_t layout_idx;
 		for (layout_idx = 0; layout_idx < num_layouts; layout_idx++) {
-			bool is_active =
-				xkb_state_layout_index_is_active(state,
-						layout_idx,
-						XKB_STATE_LAYOUT_EFFECTIVE);
+			const char *layout = xkb_keymap_layout_get_name(keymap, layout_idx);
+			json_object_array_add(layouts_arr,
+				layout ? json_object_new_string(layout) : NULL);
+
+			bool is_active = xkb_state_layout_index_is_active(state,
+				layout_idx, XKB_STATE_LAYOUT_EFFECTIVE);
 			if (is_active) {
-				const char *layout =
-					xkb_keymap_layout_get_name(keymap, layout_idx);
+				json_object_object_add(object, "xkb_active_layout_index",
+					json_object_new_int(layout_idx));
 				json_object_object_add(object, "xkb_active_layout_name",
 					layout ? json_object_new_string(layout) : NULL);
-				break;
 			}
 		}
 	}