+
+static xcb_atom_t _NET_ACTIVE_WINDOW = XCB_NONE;
+void _init_net_active_window(xcb_connection_t *conn) {
+ if (_NET_ACTIVE_WINDOW != XCB_NONE) {
+ /* already initialized */
+ return;
+ }
+ xcb_generic_error_t *err;
+ xcb_intern_atom_reply_t *atom_reply = xcb_intern_atom_reply(
+ conn,
+ xcb_intern_atom(conn, 0, strlen("_NET_ACTIVE_WINDOW"), "_NET_ACTIVE_WINDOW"),
+ &err);
+ if (atom_reply == NULL) {
+ fprintf(stderr, "X11 Error %d\n", err->error_code);
+ free(err);
+ return;
+ }
+ _NET_ACTIVE_WINDOW = atom_reply->atom;
+ free(atom_reply);
+}
+
+xcb_window_t find_focused_window(xcb_connection_t *conn, const xcb_window_t root) {
+ xcb_window_t result = XCB_NONE;
+
+ _init_net_active_window(conn);
+
+ xcb_get_property_reply_t *prop_reply = xcb_get_property_reply(
+ conn,
+ xcb_get_property_unchecked(
+ conn, false, root, _NET_ACTIVE_WINDOW, XCB_GET_PROPERTY_TYPE_ANY, 0, 1 /* word */),
+ NULL);
+ if (prop_reply == NULL) {
+ goto out;
+ }
+ if (xcb_get_property_value_length(prop_reply) == 0) {
+ goto out_prop;
+ }
+ if (prop_reply->type != XCB_ATOM_WINDOW) {
+ goto out_prop;
+ }
+
+ result = *((xcb_window_t *)xcb_get_property_value(prop_reply));
+
+out_prop:
+ free(prop_reply);
+out:
+ return result;
+}
+
+void set_focused_window(xcb_connection_t *conn, const xcb_window_t root, const xcb_window_t window) {
+ xcb_client_message_event_t ev;
+ memset(&ev, '\0', sizeof(xcb_client_message_event_t));
+
+ _init_net_active_window(conn);
+
+ ev.response_type = XCB_CLIENT_MESSAGE;
+ ev.window = window;
+ ev.type = _NET_ACTIVE_WINDOW;
+ ev.format = 32;
+ ev.data.data32[0] = 2; /* 2 = pager */
+
+ xcb_send_event(conn, false, root, XCB_EVENT_MASK_SUBSTRUCTURE_REDIRECT, (char *)&ev);
+ xcb_flush(conn);
+}