/**
 * Sencha GXT 3.0.0b - Sencha for GWT
 * Copyright(c) 2007-2012, Sencha, Inc.
 * licensing@sencha.com
 *
 * http://www.sencha.com/products/gxt/license/
 */
package com.sencha.gxt.desktop.client.widget;

import com.google.gwt.dom.client.Element;
import com.google.gwt.user.client.ui.Widget;
import com.sencha.gxt.core.client.Style.Anchor;
import com.sencha.gxt.core.client.Style.AnchorAlignment;
import com.sencha.gxt.widget.core.client.button.TextButton;
import com.sencha.gxt.widget.core.client.event.SelectEvent;
import com.sencha.gxt.widget.core.client.event.SelectEvent.SelectHandler;

/**
 * Provides a "start button" for use with the desktop. A start button is a text
 * button with a unique cell appearance. It has a start menu associated with it.
 * Clicking on the start button displays the start menu.
 */
public class StartButton extends TextButton {

  private StartMenu startMenu;
  private SelectHandler selectHandler;

  /**
   * Creates a start button using the start button cell appearance.
   */
  public StartButton() {
    super(new StartButtonCell());
    addSelectHandler(getSelectHandler());
  }

  /**
   * Returns the start menu associated with the start button.
   * 
   * @return the start menu
   */
  public StartMenu getStartMenu() {
    if (startMenu == null) {
      startMenu = new StartMenu();
    }
    return startMenu;
  }

  private SelectHandler getSelectHandler() {
    if (selectHandler == null) {
      selectHandler = new SelectHandler() {
        @Override
        public void onSelect(SelectEvent event) {
          onStartButton();
        }
      };
    }
    return selectHandler;
  }

  private void onStartButton() {
    Widget taskBar = getContainingTaskBar();
    Element alignmentElement = taskBar == null ? getElement() : taskBar.getElement();
    getStartMenu().show(alignmentElement, new AnchorAlignment(Anchor.BOTTOM_LEFT, Anchor.TOP_LEFT, true), new int[] {0, 0});
  }

  private Widget getContainingTaskBar() {
    Widget parent;
    while ((parent = getParent()) != null) {
      if (parent instanceof TaskBar) {
        return parent;
      }
    }
    return null;
  }
}