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using System;
using System.Drawing;
using System.Windows.Forms;

namespace TreeViewImage
{
    /// <summary>
    /// Расширенный древовидный вид.
    /// </summary>
    public class ExtensionView : TreeView
    {
        /// <summary>
        /// Фоновое изображение.
        /// </summary>
        Image _backgroundImage;

        /// <summary>
        /// Прямоугольник (координаты и размер) фонового изображения.
        /// </summary>
        Rectangle _imageRectangle;

        /// <summary>
        /// Конструктор по умолчанию.
        /// </summary>
        public ExtensionView() : base()
        {
            PresetStyle();
        }

        /// <summary>
        /// Конструктор со значением.
        /// </summary>
        public ExtensionView(Image backImage) : this()
        {
            PresetStyle();
            BackImage = backImage;
        }

        /// <summary>
        /// Предустановка стилей.
        /// </summary>
        private void PresetStyle()
        {
            base.SetStyle(ControlStyles.DoubleBuffer, true);
            base.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        }

        /// <summary>
        /// Фоновое изображение.
        /// </summary>
        public Image BackImage
        {
            get
            {
                return _backgroundImage;
            }
            set
            {
                if (value != null)
                {
                    _backgroundImage = value;
                    _imageRectangle.Width = _backgroundImage.Width;
                    _imageRectangle.Height = _backgroundImage.Height;

                    this.Invalidate();
                }
                else
                    throw new NullReferenceException();
            }
        }

        /// <summary>
        /// Происходит при перерисовке заднего фона.
        /// </summary>
        /// <param name="e"></param>
        protected override void OnPaintBackground(System.Windows.Forms.PaintEventArgs e)
        {
            base.OnPaintBackground(e);
            e.Graphics.DrawImage(BackImage, _imageRectangle);
        }

        /// <summary>
        /// Происходит до сворачивания.
        /// </summary>
        /// <param name="e"></param>
        protected override void OnBeforeCollapse(TreeViewCancelEventArgs e)
        {
            base.OnBeforeCollapse(e);
            //this.Invalidate(_imageRectangle);
            this.Invalidate();
        }

        /// <summary>
        /// Происходит до разворачивания.
        /// </summary>
        /// <param name="e"></param>
        protected override void OnBeforeExpand(TreeViewCancelEventArgs e)
        {
            base.OnBeforeExpand(e);
            this.Invalidate(_imageRectangle);
        }

        /// <summary>
        /// Происходит при изменение размера.
        /// </summary>
        /// <param name="e"></param>
        protected override void OnResize(EventArgs e)
        {
            _imageRectangle.X = this.Width - BackImage.Width;
            _imageRectangle.Y = this.Height - BackImage.Size.Height;
            this.Invalidate();
        }

        /// <summary>
        /// Стереть задний фон.
        /// </summary>
        private const int WM_ERASEBKGND = 0x00000014;

        /// <summary>
        /// Перерисовывать узлы автоматически, а задний фон самим.
        /// </summary>
        /// <param name="m"></param>
        protected override void WndProc(ref System.Windows.Forms.Message m)
        {
            switch(m.Msg)
            {
                case WM_ERASEBKGND:
                    bool styleUserPaint = this.GetStyle(ControlStyles.UserPaint);
                    bool styleAllPainting =     this.GetStyle(ControlStyles.AllPaintingInWmPaint);
                    this.SetStyle(ControlStyles.UserPaint, true);
                    this.SetStyle(ControlStyles.AllPaintingInWmPaint, false);
                    base.WndProc(ref m);
                    this.SetStyle(ControlStyles.UserPaint, styleUserPaint);
                    this.SetStyle(ControlStyles.AllPaintingInWmPaint, styleAllPainting);
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }

        /// <summary>
        /// Горизонтальная прокрутка.
        /// </summary>
        private const int WS_HSCROLL = 0x00100000;

        /// <summary>
        /// Убираем горизонтальную прокрутку.
        /// </summary>
        protected override CreateParams CreateParams 
        {
            get 
            {
                CreateParams parameters = base.CreateParams;
                parameters.Style |= WS_HSCROLL;
                return parameters;
            }
        }
    }
}