source: stable/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Rendering/MouseHoverLogic.cs @ 12062

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// 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.

using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Threading;

namespace ICSharpCode.AvalonEdit.Rendering
{
  /// <summary>
  /// Encapsulates and adds MouseHover support to UIElements.
  /// </summary>
  public class MouseHoverLogic : IDisposable
  {
    UIElement target;
    
    DispatcherTimer mouseHoverTimer;
    Point mouseHoverStartPoint;
    MouseEventArgs mouseHoverLastEventArgs;
    bool mouseHovering;
    
    /// <summary>
    /// Creates a new instance and attaches itself to the <paramref name="target" /> UIElement.
    /// </summary>
    public MouseHoverLogic(UIElement target)
    {
      if (target == null)
        throw new ArgumentNullException("target");
      this.target = target;
      this.target.MouseLeave += MouseHoverLogicMouseLeave;
      this.target.MouseMove += MouseHoverLogicMouseMove;
      this.target.MouseEnter += MouseHoverLogicMouseEnter;
    }
    
    void MouseHoverLogicMouseMove(object sender, MouseEventArgs e)
    {
      Vector mouseMovement = mouseHoverStartPoint - e.GetPosition(this.target);
      if (Math.Abs(mouseMovement.X) > SystemParameters.MouseHoverWidth
          || Math.Abs(mouseMovement.Y) > SystemParameters.MouseHoverHeight)
      {
        StartHovering(e);
      }
      // do not set e.Handled - allow others to also handle MouseMove
    }
    
    void MouseHoverLogicMouseEnter(object sender, MouseEventArgs e)
    {
      StartHovering(e);
      // do not set e.Handled - allow others to also handle MouseEnter
    }
    
    void StartHovering(MouseEventArgs e)
    {
      StopHovering();
      mouseHoverStartPoint = e.GetPosition(this.target);
      mouseHoverLastEventArgs = e;
      mouseHoverTimer = new DispatcherTimer(SystemParameters.MouseHoverTime, DispatcherPriority.Background, OnMouseHoverTimerElapsed, this.target.Dispatcher);
      mouseHoverTimer.Start();
    }
    
    void MouseHoverLogicMouseLeave(object sender, MouseEventArgs e)
    {
      StopHovering();
      // do not set e.Handled - allow others to also handle MouseLeave
    }
    
    void StopHovering()
    {
      if (mouseHoverTimer != null) {
        mouseHoverTimer.Stop();
        mouseHoverTimer = null;
      }
      if (mouseHovering) {
        mouseHovering = false;
        OnMouseHoverStopped(mouseHoverLastEventArgs);
      }
    }
    
    void OnMouseHoverTimerElapsed(object sender, EventArgs e)
    {
      mouseHoverTimer.Stop();
      mouseHoverTimer = null;
      
      mouseHovering = true;
      OnMouseHover(mouseHoverLastEventArgs);
    }
    
    /// <summary>
    /// Occurs when the mouse starts hovering over a certain location.
    /// </summary>
    public event EventHandler<MouseEventArgs> MouseHover;
    
    /// <summary>
    /// Raises the <see cref="MouseHover"/> event.
    /// </summary>
    protected virtual void OnMouseHover(MouseEventArgs e)
    {
      if (MouseHover != null) {
        MouseHover(this, e);
      }
    }
    
    /// <summary>
    /// Occurs when the mouse stops hovering over a certain location.
    /// </summary>
    public event EventHandler<MouseEventArgs> MouseHoverStopped;
    
    /// <summary>
    /// Raises the <see cref="MouseHoverStopped"/> event.
    /// </summary>
    protected virtual void OnMouseHoverStopped(MouseEventArgs e)
    {
      if (MouseHoverStopped != null) {
        MouseHoverStopped(this, e);
      }
    }
    
    bool disposed;
    
    /// <summary>
    /// Removes the MouseHover support from the target UIElement.
    /// </summary>
    public void Dispose()
    {
      if (!disposed) {
        this.target.MouseLeave -= MouseHoverLogicMouseLeave;
        this.target.MouseMove -= MouseHoverLogicMouseMove;
        this.target.MouseEnter -= MouseHoverLogicMouseEnter;
      }
      disposed = true;
    }
  }
}