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// hardcodet.net NotifyIcon for WPF

// Copyright (c) 2009 Philipp Sumi

// Contact and Information: http://www.hardcodet.net

//

// This library is free software; you can redistribute it and/or

// modify it under the terms of the Code Project Open License (CPOL);

// either version 1.0 of the License, or (at your option) any later

// version.

// 

// The above copyright notice and this permission notice shall be

// included in all copies or substantial portions of the Software.

// 

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

// OTHER DEALINGS IN THE SOFTWARE.

//

// THIS COPYRIGHT NOTICE MAY NOT BE REMOVED FROM THIS FILE

using System;

using System.ComponentModel;

using System.Diagnostics;

using System.Drawing;

using System.Threading;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Controls.Primitives;

using System.Windows.Interop;

using System.Windows.Threading;

using Hardcodet.Wpf.TaskbarNotification.Interop;

using Point=Hardcodet.Wpf.TaskbarNotification.Interop.Point;

namespace Hardcodet.Wpf.TaskbarNotification

{

  /// <summary>

  /// A WPF proxy to for a taskbar icon (NotifyIcon) that sits in the system's

  /// taskbar notification area ("system tray").

  /// </summary>

  public partial class TaskbarIcon : FrameworkElement, IDisposable

  {

    #region Members

    /// <summary>

    /// Represents the current icon data.

    /// </summary>

    private NotifyIconData iconData;

    /// <summary>

    /// Receives messages from the taskbar icon.

    /// </summary>

    private readonly WindowMessageSink messageSink;

    /// <summary>

    /// An action that is being invoked if the

    /// <see cref="singleClickTimer"/> fires.

    /// </summary>

    private Action delayedTimerAction;

    /// <summary>

    /// A timer that is used to differentiate between single

    /// and double clicks.

    /// </summary>

    private readonly Timer singleClickTimer;

    /// <summary>

    /// A timer that is used to close open balloon tooltips.

    /// </summary>

    private readonly Timer balloonCloseTimer;

    /// <summary>

    /// Indicates whether the taskbar icon has been created or not.

    /// </summary>

    public bool IsTaskbarIconCreated { get; private set; }

    /// <summary>

    /// Indicates whether custom tooltips are supported, which depends

    /// on the OS. Windows Vista or higher is required in order to

    /// support this feature.

    /// </summary>

    public bool SupportsCustomToolTips

    {

      get { return messageSink.Version == NotifyIconVersion.Vista; }

    }

    /// <summary>

    /// Checks whether a non-tooltip popup is currently opened.

    /// </summary>

    private bool IsPopupOpen

    {

      get

      {

        var popup = TrayPopupResolved;

        var menu = ContextMenu;

        var balloon = CustomBalloon;

        return popup != null && popup.IsOpen ||

               menu != null && menu.IsOpen ||

               balloon != null && balloon.IsOpen;

      }

    }

    #endregion

    #region Construction

    /// <summary>

    /// Inits the taskbar icon and registers a message listener

    /// in order to receive events from the taskbar area.

    /// </summary>

    public TaskbarIcon()

    {

      //using dummy sink in design mode

      messageSink = Util.IsDesignMode

                        ? WindowMessageSink.CreateEmpty()

                        : new WindowMessageSink(NotifyIconVersion.Win95);

      //init icon data structure

      iconData = NotifyIconData.CreateDefault(messageSink.MessageWindowHandle);

      //create the taskbar icon

      CreateTaskbarIcon();

      //register event listeners

      messageSink.MouseEventReceived += OnMouseEvent;

      messageSink.TaskbarCreated += OnTaskbarCreated;

      messageSink.ChangeToolTipStateRequest += OnToolTipChange;

      messageSink.BalloonToolTipChanged += OnBalloonToolTipChanged;

      //init single click / balloon timers

      singleClickTimer = new Timer(DoSingleClickAction);

      balloonCloseTimer = new Timer(CloseBalloonCallback);

      //register listener in order to get notified when the application closes

      if (Application.Current != null) Application.Current.Exit += OnExit;

    }

    #endregion

    #region Custom Balloons

    /// <summary>

    /// Shows a custom control as a tooltip in the tray location.

    /// </summary>

    /// <param name="balloon"></param>

    /// <param name="animation">An optional animation for the popup.</param>

    /// <param name="timeout">The time after which the popup is being closed.

    /// Submit null in order to keep the balloon open inde

    /// </param>

    /// <exception cref="ArgumentNullException">If <paramref name="balloon"/>

    /// is a null reference.</exception>

    public void ShowCustomBalloon(UIElement balloon, PopupAnimation animation, int? timeout)

    {

      Dispatcher dispatcher = this.GetDispatcher();

      if (!dispatcher.CheckAccess())

      {

        var action = new Action(() => ShowCustomBalloon(balloon, animation, timeout));

        dispatcher.Invoke(DispatcherPriority.Normal, action);

        return;

      }

      if (balloon == null) throw new ArgumentNullException("balloon");

      if (timeout.HasValue && timeout < 500)

      {

        string msg = "Invalid timeout of {0} milliseconds. Timeout must be at least 500 ms";

        msg = String.Format(msg, timeout); 

        throw new ArgumentOutOfRangeException("timeout", msg);

      }

      EnsureNotDisposed();

      //make sure we don't have an open balloon

      lock (this)

      {

        CloseBalloon();

      }

      //create an invisible popup that hosts the UIElement

      Popup popup = new Popup();

      popup.AllowsTransparency = true;

      //provide the popup with the taskbar icon's data context

      UpdateDataContext(popup, null, DataContext);

      //don't animate by default - devs can use attached

      //events or override

      popup.PopupAnimation = animation;

      popup.Child = balloon;

      //don't set the PlacementTarget as it causes the popup to become hidden if the

      //TaskbarIcon's parent is hidden, too...

      //popup.PlacementTarget = this;

      popup.Placement = PlacementMode.AbsolutePoint;

      popup.StaysOpen = true;

      Point position = TrayInfo.GetTrayLocation();

      popup.HorizontalOffset = position.X -1;

      popup.VerticalOffset = position.Y -1;

      //store reference

      lock (this)

      {

        SetCustomBalloon(popup);

      }

      //assign this instance as an attached property

      SetParentTaskbarIcon(balloon, this);

      //fire attached event

      RaiseBalloonShowingEvent(balloon, this);

      //display item

      popup.IsOpen = true;

      if (timeout.HasValue)

      {

        //register timer to close the popup

        balloonCloseTimer.Change(timeout.Value, Timeout.Infinite);

      }

    }

    /// <summary>

    /// Resets the closing timeout, which effectively

    /// keeps a displayed balloon message open until

    /// it is either closed programmatically through

    /// <see cref="CloseBalloon"/> or due to a new

    /// message being displayed.

    /// </summary>

    public void ResetBalloonCloseTimer()

    {

      if (IsDisposed) return;

      lock (this)

      {

        //reset timer in any case

        balloonCloseTimer.Change(Timeout.Infinite, Timeout.Infinite);

      }

    }

    /// <summary>

    /// Closes the current <see cref="CustomBalloon"/>, if the

    /// property is set.

    /// </summary>

    public void CloseBalloon()

    {

      if (IsDisposed) return;

      Dispatcher dispatcher = this.GetDispatcher();

      if (!dispatcher.CheckAccess())

      {

        Action action = CloseBalloon;

        dispatcher.Invoke(DispatcherPriority.Normal, action);

        return;

      }

      lock (this)

      {

        //reset timer in any case

        balloonCloseTimer.Change(Timeout.Infinite, Timeout.Infinite);

        //reset old popup, if we still have one

        Popup popup = CustomBalloon;

        if (popup != null)

        {

          UIElement element = popup.Child;

          //announce closing

          RoutedEventArgs eventArgs = RaiseBalloonClosingEvent(element, this);

          if (!eventArgs.Handled)

          {

            //if the event was handled, clear the reference to the popup,

            //but don't close it - the handling code has to manage this stuff now

            //close the popup

            popup.IsOpen = false;

            //reset attached property

            if (element != null) SetParentTaskbarIcon(element, null);

          }

          //remove custom balloon anyway

          SetCustomBalloon(null);

        }

      }

    }

    /// <summary>

    /// Timer-invoke event which closes the currently open balloon and

    /// resets the <see cref="CustomBalloon"/> dependency property.

    /// </summary>

    private void CloseBalloonCallback(object state)

    {

      if (IsDisposed) return;

      //switch to UI thread

      Action action = CloseBalloon;

      this.GetDispatcher().Invoke(action);

    }

    #endregion

    #region Process Incoming Mouse Events

    /// <summary>

    /// Processes mouse events, which are bubbled

    /// through the class' routed events, trigger

    /// certain actions (e.g. show a popup), or

    /// both.

    /// </summary>

    /// <param name="me">Event flag.</param>

    private void OnMouseEvent(MouseEvent me)

    {

      if (IsDisposed) return;

      switch (me)

      {

        case MouseEvent.MouseMove:

          RaiseTrayMouseMoveEvent();

          //immediately return - there's nothing left to evaluate

          return;

        case MouseEvent.IconRightMouseDown:

          RaiseTrayRightMouseDownEvent();

          break;

        case MouseEvent.IconLeftMouseDown:

          RaiseTrayLeftMouseDownEvent();

          break;

        case MouseEvent.IconRightMouseUp:

          RaiseTrayRightMouseUpEvent();

          break;

        case MouseEvent.IconLeftMouseUp:

          RaiseTrayLeftMouseUpEvent();

          break;

        case MouseEvent.IconMiddleMouseDown:

          RaiseTrayMiddleMouseDownEvent();

          break;

        case MouseEvent.IconMiddleMouseUp:

          RaiseTrayMiddleMouseUpEvent();

          break;

        case MouseEvent.IconDoubleClick:

          //cancel single click timer

          singleClickTimer.Change(Timeout.Infinite, Timeout.Infinite);

          //bubble event

          RaiseTrayMouseDoubleClickEvent();

          break;

        case MouseEvent.BalloonToolTipClicked:

          RaiseTrayBalloonTipClickedEvent();

          break;

        default:

          throw new ArgumentOutOfRangeException("me", "Missing handler for mouse event flag: " + me);

      }

      //get mouse coordinates

      Point cursorPosition = new Point();

      WinApi.GetCursorPos(ref cursorPosition);

      bool isLeftClickCommandInvoked = false;

      //show popup, if requested

      if (me.IsMatch(PopupActivation))

      {

        if (me == MouseEvent.IconLeftMouseUp)

        {

          //show popup once we are sure it's not a double click

          delayedTimerAction = () =>

                                 {

                                   LeftClickCommand.ExecuteIfEnabled(LeftClickCommandParameter, LeftClickCommandTarget ?? this);

                                   ShowTrayPopup(cursorPosition);

                                 };

          singleClickTimer.Change(WinApi.GetDoubleClickTime(), Timeout.Infinite);

          isLeftClickCommandInvoked = true;

        }

        else

        {

          //show popup immediately

          ShowTrayPopup(cursorPosition);

        }

      }

      //show context menu, if requested

      if (me.IsMatch(MenuActivation))

      {

        if (me == MouseEvent.IconLeftMouseUp)

        {

          //show context menu once we are sure it's not a double click

          delayedTimerAction = () =>

                                 {

                                   LeftClickCommand.ExecuteIfEnabled(LeftClickCommandParameter, LeftClickCommandTarget ?? this);

                                   ShowContextMenu(cursorPosition);

                                 };

          singleClickTimer.Change(WinApi.GetDoubleClickTime(), Timeout.Infinite);

          isLeftClickCommandInvoked = true;

        }

        else

        {

          //show context menu immediately

          ShowContextMenu(cursorPosition);

        }

      }

      //make sure the left click command is invoked on mouse clicks

      if (me == MouseEvent.IconLeftMouseUp && !isLeftClickCommandInvoked)

      {

        //show context menu once we are sure it's not a double click

        delayedTimerAction = () => LeftClickCommand.ExecuteIfEnabled(LeftClickCommandParameter, LeftClickCommandTarget ?? this);

        singleClickTimer.Change(WinApi.GetDoubleClickTime(), Timeout.Infinite);

      }

    }

    #endregion

    #region ToolTips

    /// <summary>

    /// Displays a custom tooltip, if available. This method is only

    /// invoked for Windows Vista and above.

    /// </summary>

    /// <param name="visible">Whether to show or hide the tooltip.</param>

    private void OnToolTipChange(bool visible)

    {

      //if we don't have a tooltip, there's nothing to do here...

      if (TrayToolTipResolved == null) return;

      if (visible)

      {

        if (IsPopupOpen)

        {

          //ignore if we are already displaying something down there

          return;

        }

        var args = RaisePreviewTrayToolTipOpenEvent();

        if (args.Handled) return;

        TrayToolTipResolved.IsOpen = true;

        //raise attached event first

        if (TrayToolTip != null) RaiseToolTipOpenedEvent(TrayToolTip);

        //bubble routed event

        RaiseTrayToolTipOpenEvent();

      }

      else

      {

        var args = RaisePreviewTrayToolTipCloseEvent();

        if (args.Handled) return;

        //raise attached event first

        if (TrayToolTip != null) RaiseToolTipCloseEvent(TrayToolTip);

        TrayToolTipResolved.IsOpen = false;

        //bubble event

        RaiseTrayToolTipCloseEvent();

      }

    }

    /// <summary>

    /// Creates a <see cref="ToolTip"/> control that either

    /// wraps the currently set <see cref="TrayToolTip"/>

    /// control or the <see cref="ToolTipText"/> string.<br/>

    /// If <see cref="TrayToolTip"/> itself is already

    /// a <see cref="ToolTip"/> instance, it will be used directly.

    /// </summary>

    /// <remarks>We use a <see cref="ToolTip"/> rather than

    /// <see cref="Popup"/> because there was no way to prevent a

    /// popup from causing cyclic open/close commands if it was

    /// placed under the mouse. ToolTip internally uses a Popup of

    /// its own, but takes advance of Popup's internal <see cref="Popup.HitTestable"/>

    /// property which prevents this issue.</remarks>

    private void CreateCustomToolTip()

    {

      //check if the item itself is a tooltip

      ToolTip tt = TrayToolTip as ToolTip;

      if (tt == null && TrayToolTip != null)

      {

        //create an invisible tooltip that hosts the UIElement

        tt = new ToolTip();

        tt.Placement = PlacementMode.Mouse;

        //do *not* set the placement target, as it causes the popup to become hidden if the

        //TaskbarIcon's parent is hidden, too. At runtime, the parent can be resolved through

        //the ParentTaskbarIcon attached dependency property:

        //tt.PlacementTarget = this;

        //make sure the tooltip is invisible

        tt.HasDropShadow = false;

        tt.BorderThickness = new Thickness(0);

        tt.Background = System.Windows.Media.Brushes.Transparent;

        //setting the 

        tt.StaysOpen = true;

        tt.Content = TrayToolTip;

      }

      else if (tt == null && !String.IsNullOrEmpty(ToolTipText))

      {

        //create a simple tooltip for the string

        tt = new ToolTip();

        tt.Content = ToolTipText;

      }

      //the tooltip explicitly gets the DataContext of this instance.

      //If there is no DataContext, the TaskbarIcon assigns itself

      if (tt != null)

      {

        UpdateDataContext(tt, null, DataContext);

      }

      //store a reference to the used tooltip

      SetTrayToolTipResolved(tt);

    }

    /// <summary>

    /// Sets tooltip settings for the class depending on defined

    /// dependency properties and OS support.

    /// </summary>

    private void WriteToolTipSettings()

    {

      const IconDataMembers flags = IconDataMembers.Tip;

      iconData.ToolTipText = ToolTipText;

      if (messageSink.Version == NotifyIconVersion.Vista)

      {

        //we need to set a tooltip text to get tooltip events from the

        //taskbar icon

        if (String.IsNullOrEmpty(iconData.ToolTipText) && TrayToolTipResolved != null)

        {

          //if we have not tooltip text but a custom tooltip, we

          //need to set a dummy value (we're displaying the ToolTip control, not the string)

          iconData.ToolTipText = "ToolTip";

        }

      }

      //update the tooltip text

      Util.WriteIconData(ref iconData, NotifyCommand.Modify, flags);

    }

    #endregion

    #region Custom Popup

    /// <summary>

    /// Creates a <see cref="ToolTip"/> control that either

    /// wraps the currently set <see cref="TrayToolTip"/>

    /// control or the <see cref="ToolTipText"/> string.<br/>

    /// If <see cref="TrayToolTip"/> itself is already

    /// a <see cref="ToolTip"/> instance, it will be used directly.

    /// </summary>

    /// <remarks>We use a <see cref="ToolTip"/> rather than

    /// <see cref="Popup"/> because there was no way to prevent a

    /// popup from causing cyclic open/close commands if it was

    /// placed under the mouse. ToolTip internally uses a Popup of

    /// its own, but takes advance of Popup's internal <see cref="Popup.HitTestable"/>

    /// property which prevents this issue.</remarks>

    private void CreatePopup()

    {

      //check if the item itself is a popup

      Popup popup = TrayPopup as Popup;

      if (popup == null && TrayPopup != null)

      {

        //create an invisible popup that hosts the UIElement

        popup = new Popup();

        popup.AllowsTransparency = true;

        //don't animate by default - devs can use attached

        //events or override

        popup.PopupAnimation = PopupAnimation.None;

        //the CreateRootPopup method outputs binding errors in the debug window because

        //it tries to bind to "Popup-specific" properties in case they are provided by the child.

        //We don't need that so just assign the control as the child.

        popup.Child = TrayPopup;

        //do *not* set the placement target, as it causes the popup to become hidden if the

        //TaskbarIcon's parent is hidden, too. At runtime, the parent can be resolved through

        //the ParentTaskbarIcon attached dependency property:

        //popup.PlacementTarget = this;

        popup.Placement = PlacementMode.AbsolutePoint;

        popup.StaysOpen = false;

      }

      //the popup explicitly gets the DataContext of this instance.

      //If there is no DataContext, the TaskbarIcon assigns itself

      if (popup != null)

      {

        UpdateDataContext(popup, null, DataContext);

      }

      //store a reference to the used tooltip

      SetTrayPopupResolved(popup);

    }

    /// <summary>

    /// Displays the <see cref="TrayPopup"/> control if

    /// it was set.

    /// </summary>

    private void ShowTrayPopup(Point cursorPosition)

    {

      if (IsDisposed) return;

      //raise preview event no matter whether popup is currently set

      //or not (enables client to set it on demand)

      var args = RaisePreviewTrayPopupOpenEvent();

      if (args.Handled) return;

      if (TrayPopup != null)

      {

        //use absolute position, but place the popup centered above the icon

        TrayPopupResolved.Placement = PlacementMode.AbsolutePoint;

        TrayPopupResolved.HorizontalOffset = cursorPosition.X;

        TrayPopupResolved.VerticalOffset = cursorPosition.Y;

        //open popup

        TrayPopupResolved.IsOpen = true;

        IntPtr handle = IntPtr.Zero;

        if (TrayPopupResolved.Child != null)

        {

          //try to get a handle on the popup itself (via its child)

          HwndSource source = (HwndSource)PresentationSource.FromVisual(TrayPopupResolved.Child);

          if (source != null) handle = source.Handle;

        }

        //if we don't have a handle for the popup, fall back to the message sink

        if (handle == IntPtr.Zero) handle = messageSink.MessageWindowHandle;

        //activate either popup or message sink to track deactivation.

        //otherwise, the popup does not close if the user clicks somewhere else

        WinApi.SetForegroundWindow(handle);

        //raise attached event - item should never be null unless developers

        //changed the CustomPopup directly...

        if (TrayPopup != null) RaisePopupOpenedEvent(TrayPopup);

        //bubble routed event

        RaiseTrayPopupOpenEvent();

      }

    }

    #endregion

    #region Context Menu

    /// <summary>

    /// Displays the <see cref="ContextMenu"/> if

    /// it was set.

    /// </summary>

    private void ShowContextMenu(Point cursorPosition)

    {

      if (IsDisposed) return;

      //raise preview event no matter whether context menu is currently set

      //or not (enables client to set it on demand)

      var args = RaisePreviewTrayContextMenuOpenEvent();

      if (args.Handled) return;

      if (ContextMenu != null)

      {

        //use absolute position

        ContextMenu.Placement = PlacementMode.AbsolutePoint;

        ContextMenu.HorizontalOffset = cursorPosition.X;

        ContextMenu.VerticalOffset = cursorPosition.Y;

        ContextMenu.IsOpen = true;

        //activate the message window to track deactivation - otherwise, the context menu

        //does not close if the user clicks somewhere else

        WinApi.SetForegroundWindow(messageSink.MessageWindowHandle);

        //bubble event

        RaiseTrayContextMenuOpenEvent();

      }

    }

    #endregion

    #region Balloon Tips

    /// <summary>

    /// Bubbles events if a balloon ToolTip was displayed

    /// or removed.

    /// </summary>

    /// <param name="visible">Whether the ToolTip was just displayed

    /// or removed.</param>

    private void OnBalloonToolTipChanged(bool visible)

    {

      if (visible)

      {

        RaiseTrayBalloonTipShownEvent();

      }

      else

      {

        RaiseTrayBalloonTipClosedEvent();

      }

    }

    /// <summary>

    /// Displays a balloon tip with the specified title,

    /// text, and icon in the taskbar for the specified time period.

    /// </summary>

    /// <param name="title">The title to display on the balloon tip.</param>

    /// <param name="message">The text to display on the balloon tip.</param>

    /// <param name="symbol">A symbol that indicates the severity.</param>

    public void ShowBalloonTip(string title, string message, BalloonIcon symbol)

    {

      lock (this)

      {

        ShowBalloonTip(title, message, symbol.GetBalloonFlag(), IntPtr.Zero);

      }

    }

    /// <summary>

    /// Displays a balloon tip with the specified title,

    /// text, and a custom icon in the taskbar for the specified time period.

    /// </summary>

    /// <param name="title">The title to display on the balloon tip.</param>

    /// <param name="message">The text to display on the balloon tip.</param>

    /// <param name="customIcon">A custom icon.</param>

    /// <exception cref="ArgumentNullException">If <paramref name="customIcon"/>

    /// is a null reference.</exception>

    public void ShowBalloonTip(string title, string message, Icon customIcon)

    {

      if (customIcon == null) throw new ArgumentNullException("customIcon");

      lock (this)

      {

        ShowBalloonTip(title, message, BalloonFlags.User, customIcon.Handle);

      }

    }

    /// <summary>

    /// Invokes <see cref="WinApi.Shell_NotifyIcon"/> in order to display

    /// a given balloon ToolTip.

    /// </summary>

    /// <param name="title">The title to display on the balloon tip.</param>

    /// <param name="message">The text to display on the balloon tip.</param>

    /// <param name="flags">Indicates what icon to use.</param>

    /// <param name="balloonIconHandle">A handle to a custom icon, if any, or

    /// <see cref="IntPtr.Zero"/>.</param>

    private void ShowBalloonTip(string title, string message, BalloonFlags flags, IntPtr balloonIconHandle)

    {

      EnsureNotDisposed();

      iconData.BalloonText = message ?? String.Empty;

      iconData.BalloonTitle = title ?? String.Empty;

      iconData.BalloonFlags = flags;

      iconData.CustomBalloonIconHandle = balloonIconHandle;

      Util.WriteIconData(ref iconData, NotifyCommand.Modify, IconDataMembers.Info | IconDataMembers.Icon);

    }

    /// <summary>

    /// Hides a balloon ToolTip, if any is displayed.

    /// </summary>

    public void HideBalloonTip()

    {

      EnsureNotDisposed();

      //reset balloon by just setting the info to an empty string

      iconData.BalloonText = iconData.BalloonTitle = String.Empty;

      Util.WriteIconData(ref iconData, NotifyCommand.Modify, IconDataMembers.Info);

    }

    #endregion

    #region Single Click Timer event

    /// <summary>

    /// Performs a delayed action if the user requested an action

    /// based on a single click of the left mouse.<br/>

    /// This method is invoked by the <see cref="singleClickTimer"/>.

    /// </summary>

    private void DoSingleClickAction(object state)

    {

      if (IsDisposed) return;

      //run action

      Action action = delayedTimerAction;

      if (action != null)

      {

        //cleanup action

        delayedTimerAction = null;

        //switch to UI thread

        this.GetDispatcher().Invoke(action);

      }

    }

    #endregion

    #region Set Version (API)

    /// <summary>

    /// Sets the version flag for the <see cref="iconData"/>.

    /// </summary>

    private void SetVersion()

    {

      iconData.VersionOrTimeout = (uint) NotifyIconVersion.Vista;

      bool status = WinApi.Shell_NotifyIcon(NotifyCommand.SetVersion, ref iconData);

      if (!status)

      {

        iconData.VersionOrTimeout = (uint) NotifyIconVersion.Win2000;

        status = Util.WriteIconData(ref iconData, NotifyCommand.SetVersion);

      }

      if (!status)

      {

        iconData.VersionOrTimeout = (uint) NotifyIconVersion.Win95;

        status = Util.WriteIconData(ref iconData, NotifyCommand.SetVersion);

      }

      if (!status)

      {

        Debug.Fail("Could not set version");

      }

    }

    #endregion

    #region Create / Remove Taskbar Icon

    /// <summary>

    /// Recreates the taskbar icon if the whole taskbar was

    /// recreated (e.g. because Explorer was shut down).

    /// </summary>

    private void OnTaskbarCreated()

    {

      IsTaskbarIconCreated = false;

      CreateTaskbarIcon();

    }

    /// <summary>

    /// Creates the taskbar icon. This message is invoked during initialization,

    /// if the taskbar is restarted, and whenever the icon is displayed.

    /// </summary>

    private void CreateTaskbarIcon()

    {

      lock (this)

      {

        if (!IsTaskbarIconCreated)

        {

          const IconDataMembers members = IconDataMembers.Message

                                          | IconDataMembers.Icon

                                          | IconDataMembers.Tip;

          //write initial configuration

          var status = Util.WriteIconData(ref iconData, NotifyCommand.Add, members);

          if (!status)

          {

            throw new Win32Exception("Could not create icon data");

          }

          //set to most recent version

          SetVersion();

          messageSink.Version = (NotifyIconVersion) iconData.VersionOrTimeout;

          IsTaskbarIconCreated = true;

        }

      }

    }

    /// <summary>

    /// Closes the taskbar icon if required.

    /// </summary>

    private void RemoveTaskbarIcon()

    {

      lock (this)

      {

        if (IsTaskbarIconCreated)

        {

          Util.WriteIconData(ref iconData, NotifyCommand.Delete, IconDataMembers.Message);

          IsTaskbarIconCreated = false;

        }

      }

    }

    #endregion

    #region Dispose / Exit

    /// <summary>

    /// Set to true as soon as <see cref="Dispose"/>

    /// has been invoked.

    /// </summary>

    public bool IsDisposed { get; private set; }

    /// <summary>

    /// Checks if the object has been disposed and

    /// raises a <see cref="ObjectDisposedException"/> in case

    /// the <see cref="IsDisposed"/> flag is true.

    /// </summary>

    private void EnsureNotDisposed()

    {

      if (IsDisposed) throw new ObjectDisposedException(Name ?? GetType().FullName);

    }

    /// <summary>

    /// Disposes the class if the application exits.

    /// </summary>

    private void OnExit(object sender, EventArgs e)

    {

      Dispose();

    }

    /// <summary>

    /// This destructor will run only if the <see cref="Dispose()"/>

    /// method does not get called. This gives this base class the

    /// opportunity to finalize.

    /// <para>

    /// Important: Do not provide destructors in types derived from

    /// this class.

    /// </para>

    /// </summary>

    ~TaskbarIcon()

    {

      Dispose(false);

    }

    /// <summary>

    /// Disposes the object.

    /// </summary>

    /// <remarks>This method is not virtual by design. Derived classes

    /// should override <see cref="Dispose(bool)"/>.

    /// </remarks>

    public void Dispose()

    {

      Dispose(true);

      // This object will be cleaned up by the Dispose method.

      // Therefore, you should call GC.SupressFinalize to

      // take this object off the finalization queue 

      // and prevent finalization code for this object

      // from executing a second time.

      GC.SuppressFinalize(this);

    }

    /// <summary>

    /// Closes the tray and releases all resources.

    /// </summary>

    /// <summary>

    /// <c>Dispose(bool disposing)</c> executes in two distinct scenarios.

    /// If disposing equals <c>true</c>, the method has been called directly

    /// or indirectly by a user's code. Managed and unmanaged resources

    /// can be disposed.

    /// </summary>

    /// <param name="disposing">If disposing equals <c>false</c>, the method

    /// has been called by the runtime from inside the finalizer and you

    /// should not reference other objects. Only unmanaged resources can

    /// be disposed.</param>

    /// <remarks>Check the <see cref="IsDisposed"/> property to determine whether

    /// the method has already been called.</remarks>

    private void Dispose(bool disposing)

    {

      //don't do anything if the component is already disposed

      if (IsDisposed || !disposing) return;

      lock (this)

      {

        IsDisposed = true;

        //deregister application event listener

        if (Application.Current != null)

        {

          Application.Current.Exit -= OnExit;

        }

        //stop timers

        singleClickTimer.Dispose();

        balloonCloseTimer.Dispose();

        //dispose message sink

        messageSink.Dispose();

        //remove icon

        RemoveTaskbarIcon();

      }

    }

    #endregion

  }

}