clear_state() {
   this.state = {history: [], index: -1};
   return this.state_changed.emit(undefined);
 }

this.throttled_paint = throttle((() => this.force_paint.emit(undefined)), 15); // TODO (bev) configurable

 window._bokeh_gmaps_callback = () => gmaps_ready.emit(undefined);

 update({xs, ys}) {
   this.setv({xs, ys, screen: true}, {silent: true});
   return this.data_update.emit();
 }

 update({left, right, top, bottom}) {
   this.setv({left, right, top, bottom, screen: true}, {silent: true});
   this.data_update.emit();
 }