wpftoolkit/ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DropDownButton/Implementation/DropDownButton.cs

/************************************************************************

   Extended WPF Toolkit

   Copyright (C) 2010-2012 Xceed Software Inc.

   This program is provided to you under the terms of the Microsoft Public
   License (Ms-PL) as published at http://wpftoolkit.codeplex.com/license 

   This program can be provided to you by Xceed Software Inc. under a
   proprietary commercial license agreement for use in non-Open Source
   projects. The commercial version of Extended WPF Toolkit also includes
   priority technical support, commercial updates, and many additional 
   useful WPF controls if you license Xceed Business Suite for WPF.

   Visit http://xceed.com and follow @datagrid on Twitter.

  **********************************************************************/

using System;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;

namespace Xceed.Wpf.Toolkit
{
  [TemplatePart( Name = PART_DropDownButton, Type = typeof( ToggleButton ) )]
  public class DropDownButton : ContentControl, ICommandSource
  {
    private const string PART_DropDownButton = "PART_DropDownButton";

    #region Constructors

    static DropDownButton()
    {
      DefaultStyleKeyProperty.OverrideMetadata( typeof( DropDownButton ), new FrameworkPropertyMetadata( typeof( DropDownButton ) ) );
    }

    public DropDownButton()
    {
      Keyboard.AddKeyDownHandler( this, OnKeyDown );
      Mouse.AddPreviewMouseDownOutsideCapturedElementHandler( this, OnMouseDownOutsideCapturedElement );
    }

    #endregion //Constructors

    #region Properties

    private System.Windows.Controls.Primitives.ButtonBase _button;
    protected System.Windows.Controls.Primitives.ButtonBase Button
    {
      get
      {
        return _button;
      }
      set
      {
        if( _button != null )
          _button.Click -= DropDownButton_Click;

        _button = value;

        if( _button != null )
          _button.Click += DropDownButton_Click;
      }
    }

    #region DropDownContent

    public static readonly DependencyProperty DropDownContentProperty = DependencyProperty.Register( "DropDownContent", typeof( object ), typeof( DropDownButton ), new UIPropertyMetadata( null, OnDropDownContentChanged ) );
    public object DropDownContent
    {
      get
      {
        return ( object )GetValue( DropDownContentProperty );
      }
      set
      {
        SetValue( DropDownContentProperty, value );
      }
    }

    private static void OnDropDownContentChanged( DependencyObject o, DependencyPropertyChangedEventArgs e )
    {
      DropDownButton dropDownButton = o as DropDownButton;
      if( dropDownButton != null )
        dropDownButton.OnDropDownContentChanged( ( object )e.OldValue, ( object )e.NewValue );
    }

    protected virtual void OnDropDownContentChanged( object oldValue, object newValue )
    {
      // TODO: Add your property changed side-effects. Descendants can override as well.
    }

    #endregion //DropDownContent

    #region IsOpen

    public static readonly DependencyProperty IsOpenProperty = DependencyProperty.Register( "IsOpen", typeof( bool ), typeof( DropDownButton ), new UIPropertyMetadata( false, OnIsOpenChanged ) );
    public bool IsOpen
    {
      get
      {
        return ( bool )GetValue( IsOpenProperty );
      }
      set
      {
        SetValue( IsOpenProperty, value );
      }
    }

    private static void OnIsOpenChanged( DependencyObject o, DependencyPropertyChangedEventArgs e )
    {
      DropDownButton dropDownButton = o as DropDownButton;
      if( dropDownButton != null )
        dropDownButton.OnIsOpenChanged( ( bool )e.OldValue, ( bool )e.NewValue );
    }

    protected virtual void OnIsOpenChanged( bool oldValue, bool newValue )
    {
      if( newValue )
        RaiseRoutedEvent( DropDownButton.OpenedEvent );
      else
        RaiseRoutedEvent( DropDownButton.ClosedEvent );
    }

    #endregion //IsOpen

    #endregion //Properties

    #region Base Class Overrides

    public override void OnApplyTemplate()
    {
      base.OnApplyTemplate();
      Button = GetTemplateChild( PART_DropDownButton ) as ToggleButton;
    }

    #endregion //Base Class Overrides

    #region Events

    public static readonly RoutedEvent ClickEvent = EventManager.RegisterRoutedEvent( "Click", RoutingStrategy.Bubble, typeof( RoutedEventHandler ), typeof( DropDownButton ) );
    public event RoutedEventHandler Click
    {
      add
      {
        AddHandler( ClickEvent, value );
      }
      remove
      {
        RemoveHandler( ClickEvent, value );
      }
    }

    public static readonly RoutedEvent OpenedEvent = EventManager.RegisterRoutedEvent( "Opened", RoutingStrategy.Bubble, typeof( RoutedEventHandler ), typeof( DropDownButton ) );
    public event RoutedEventHandler Opened
    {
      add
      {
        AddHandler( OpenedEvent, value );
      }
      remove
      {
        RemoveHandler( OpenedEvent, value );
      }
    }

    public static readonly RoutedEvent ClosedEvent = EventManager.RegisterRoutedEvent( "Closed", RoutingStrategy.Bubble, typeof( RoutedEventHandler ), typeof( DropDownButton ) );
    public event RoutedEventHandler Closed
    {
      add
      {
        AddHandler( ClosedEvent, value );
      }
      remove
      {
        RemoveHandler( ClosedEvent, value );
      }
    }

    #endregion //Events

    #region Event Handlers

    private void OnKeyDown( object sender, KeyEventArgs e )
    {
      switch( e.Key )
      {
        case Key.Escape:
          {
            CloseDropDown();
            break;
          }
      }
    }

    private void OnMouseDownOutsideCapturedElement( object sender, MouseButtonEventArgs e )
    {
      CloseDropDown();
    }

    private void DropDownButton_Click( object sender, RoutedEventArgs e )
    {
      OnClick();
    }

    void CanExecuteChanged( object sender, EventArgs e )
    {
      CanExecuteChanged();
    }

    #endregion //Event Handlers

    #region Methods

    private void CanExecuteChanged()
    {
      if( Command != null )
      {
        RoutedCommand command = Command as RoutedCommand;

        // If a RoutedCommand.
        if( command != null )
          IsEnabled = command.CanExecute( CommandParameter, CommandTarget ) ? true : false;
        // If a not RoutedCommand.
        else
          IsEnabled = Command.CanExecute( CommandParameter ) ? true : false;
      }
    }

    /// <summary>
    /// Closes the drop down.
    /// </summary>
    private void CloseDropDown()
    {
      if( IsOpen )
        IsOpen = false;
      ReleaseMouseCapture();
    }

    protected virtual void OnClick()
    {
      RaiseRoutedEvent( DropDownButton.ClickEvent );
      RaiseCommand();
    }

    /// <summary>
    /// Raises routed events.
    /// </summary>
    private void RaiseRoutedEvent( RoutedEvent routedEvent )
    {
      RoutedEventArgs args = new RoutedEventArgs( routedEvent, this );
      RaiseEvent( args );
    }

    /// <summary>
    /// Raises the command's Execute event.
    /// </summary>
    private void RaiseCommand()
    {
      if( Command != null )
      {
        RoutedCommand routedCommand = Command as RoutedCommand;

        if( routedCommand == null )
          ( ( ICommand )Command ).Execute( CommandParameter );
        else
          routedCommand.Execute( CommandParameter, CommandTarget );
      }
    }

    /// <summary>
    /// Unhooks a command from the Command property.
    /// </summary>
    /// <param name="oldCommand">The old command.</param>
    /// <param name="newCommand">The new command.</param>
    private void UnhookCommand( ICommand oldCommand, ICommand newCommand )
    {
      EventHandler handler = CanExecuteChanged;
      oldCommand.CanExecuteChanged -= handler;
    }

    /// <summary>
    /// Hooks up a command to the CanExecuteChnaged event handler.
    /// </summary>
    /// <param name="oldCommand">The old command.</param>
    /// <param name="newCommand">The new command.</param>
    private void HookUpCommand( ICommand oldCommand, ICommand newCommand )
    {
      EventHandler handler = new EventHandler( CanExecuteChanged );
      canExecuteChangedHandler = handler;
      if( newCommand != null )
        newCommand.CanExecuteChanged += canExecuteChangedHandler;
    }

    #endregion //Methods

    #region ICommandSource Members

    // Keeps a copy of the CanExecuteChnaged handler so it doesn't get garbage collected.
    private EventHandler canExecuteChangedHandler;

    #region Command

    public static readonly DependencyProperty CommandProperty = DependencyProperty.Register( "Command", typeof( ICommand ), typeof( DropDownButton ), new PropertyMetadata( ( ICommand )null, OnCommandChanged ) );
    [TypeConverter( typeof( CommandConverter ) )]
    public ICommand Command
    {
      get
      {
        return ( ICommand )GetValue( CommandProperty );
      }
      set
      {
        SetValue( CommandProperty, value );
      }
    }

    private static void OnCommandChanged( DependencyObject d, DependencyPropertyChangedEventArgs e )
    {
      DropDownButton dropDownButton = d as DropDownButton;
      if( dropDownButton != null )
        dropDownButton.OnCommandChanged( ( ICommand )e.OldValue, ( ICommand )e.NewValue );
    }

    protected virtual void OnCommandChanged( ICommand oldValue, ICommand newValue )
    {
      // If old command is not null, then we need to remove the handlers.
      if( oldValue != null )
        UnhookCommand( oldValue, newValue );

      HookUpCommand( oldValue, newValue );

      CanExecuteChanged(); //may need to call this when changing the command parameter or target.
    }

    #endregion //Command

    public static readonly DependencyProperty CommandParameterProperty = DependencyProperty.Register( "CommandParameter", typeof( object ), typeof( DropDownButton ), new PropertyMetadata( null ) );
    public object CommandParameter
    {
      get
      {
        return GetValue( CommandParameterProperty );
      }
      set
      {
        SetValue( CommandParameterProperty, value );
      }
    }

    public static readonly DependencyProperty CommandTargetProperty = DependencyProperty.Register( "CommandTarget", typeof( IInputElement ), typeof( DropDownButton ), new PropertyMetadata( null ) );
    public IInputElement CommandTarget
    {
      get
      {
        return ( IInputElement )GetValue( CommandTargetProperty );
      }
      set
      {
        SetValue( CommandTargetProperty, value );
      }
    }

    #endregion //ICommandSource Members
  }
}