text: // Copyright 2019 The Druid Authors.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  use druid::widget::{Checkbox, Either, Flex, Label, Slider};
  use druid::{AppLauncher, Data, Lens, LocalizedString, Widget, WidgetExt, WindowDesc};
  
  #[derive(Clone, Default, Data, Lens)]
  struct AppState {
      which: bool,
      value: f64,
  }
  
  pub fn main() {
      let main_window = WindowDesc::new(ui_builder).title(
          LocalizedString::new("either-demo-window-title")
              .with_placeholder("Switcheroo")
              .with_arg("view", |data: &AppState, _env| (data.which as u8).into()),
      );
      let data = AppState::default();
      AppLauncher::with_window(main_window)
          .use_simple_logger()
          .launch(data)
          .expect("launch failed");
  }
  
  fn ui_builder() -> impl Widget<AppState> {
      let label = Label::new("Click to reveal slider");
  
      let mut col = Flex::column();
      col.add_child(
          Checkbox::new("Toggle slider")
              .lens(AppState::which)
              .padding(5.0),
      );
      let either = Either::new(
          |data, _env| data.which,
          Slider::new().lens(AppState::value).padding(5.0),
          label.padding(5.0),
      );
      col.add_child(either);
      col
  }
  