java/com/google/gwtexpui/globalkey/client/ShowHelpCommand.java

// Copyright (C) 2009 The Android Open Source Project
//
// 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.

package com.google.gwtexpui.globalkey.client;

import com.google.gwt.event.dom.client.FocusEvent;
import com.google.gwt.event.dom.client.FocusHandler;
import com.google.gwt.event.dom.client.KeyPressEvent;
import com.google.gwt.event.logical.shared.CloseEvent;
import com.google.gwt.event.logical.shared.CloseHandler;
import com.google.gwt.event.shared.EventBus;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.event.shared.SimpleEventBus;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.PopupPanel;
import com.google.gwt.user.client.ui.PopupPanel.PositionCallback;

public class ShowHelpCommand extends KeyCommand {
  public static final ShowHelpCommand INSTANCE = new ShowHelpCommand();
  private static final EventBus BUS = new SimpleEventBus();
  private static KeyHelpPopup current;

  public static HandlerRegistration addFocusHandler(FocusHandler fh) {
    return BUS.addHandler(FocusEvent.getType(), fh);
  }

  public ShowHelpCommand() {
    super(0, '?', KeyConstants.I.showHelp());
  }

  @Override
  public void onKeyPress(KeyPressEvent event) {
    if (current != null) {
      // Already open? Close the dialog.
      //
      current.hide();
      return;
    }

    final KeyHelpPopup help = new KeyHelpPopup();
    help.addCloseHandler(
        new CloseHandler<PopupPanel>() {
          @Override
          public void onClose(CloseEvent<PopupPanel> event) {
            current = null;
            BUS.fireEvent(new FocusEvent() {});
          }
        });
    current = help;
    help.setPopupPositionAndShow(
        new PositionCallback() {
          @Override
          public void setPosition(int pWidth, int pHeight) {
            final int left = (Window.getClientWidth() - pWidth) >> 1;
            final int wLeft = Window.getScrollLeft();
            final int wTop = Window.getScrollTop();
            help.setPopupPosition(wLeft + left, wTop + 50);
          }
        });
  }
}