Implementing WS-SecureConversation in Microsoft IssueVision

using System;
using System.Data;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace IssueVision
{
	// Displays the history list. Uses an owner draw listbox. Maintains 
	// an offscreen bitmap to draw each item to prevent flickering when
	// the control is resized.
	public class HistoryList : ListBox
	{
		// data that is attached to each row in the list
		private struct RowItem
		{
			public bool IsHeader;
			public string DisplayName;
			public string Comment;
			public string DateCreated;
			
			// init the item
			public RowItem(bool isHeader, string displayName, string comment, DateTime dateCreated)
			{
				IsHeader = isHeader;
				DisplayName = displayName;
				Comment = comment;
				
				if (dateCreated != DateTime.MinValue)
					DateCreated = string.Format("{0} {1}", dateCreated.ToShortDateString(), dateCreated.ToShortTimeString()).ToLower();
				else
					DateCreated = string.Empty;
			}
		}

		private class Consts
		{
			// cell space in each row
			public const int Buffer = 4;
			// where to draw the second column of information (from right side)
			public const int RightBuffer = 120;
			// don't draw the second column if the control is only this wide
			public const int DrawRightSideWidth = 210;
		}

		// internal members
		private Font m_fontHeader;
		private StringFormat m_format;
		
		// maintain offscreen bitmap to prevent flickering
		private Bitmap m_bmpItem;
		private Graphics m_graphics;

		// updating the contents of the list
		public new DataRow[] DataSource
		{
			set
			{
				// delete any existing items
				Clear();
				
				// go through and add rows to the list
				if (value != null)
				{
					foreach (DataRow row in value)
					{
						Items.Add(new RowItem(false, (string)row["DisplayName"], (string)row["Comment"], (DateTime)row["DateCreated"]));
					}
				}
			}
		}

		public HistoryList()
		{
			// owner draw, variable height so can draw the header 
			// with a different height
			DrawMode = DrawMode.OwnerDrawVariable;
			
			// font used when drawing the header
			m_fontHeader = new Font("tahoma", Font.Size, FontStyle.Bold);
			
			// format used when drawing comments
			m_format = new StringFormat();
			m_format.Trimming = StringTrimming.EllipsisCharacter;
		}

		// remove all items from the list
		public void Clear()
		{
			// delete all items
			Items.Clear();
			
			// always add the header as the first item
			Items.Add(new RowItem(true, string.Empty, string.Empty, DateTime.MinValue));
			
			Invalidate();
		}

		// calculate the height of the row
		protected override void OnMeasureItem(MeasureItemEventArgs e)
		{
			base.OnMeasureItem(e);
			
			if (e.Index >= 0)
			{
				// header is index 0, others are data items
				if (e.Index == 0)
				{
					e.ItemHeight = Font.Height + (Consts.Buffer * 3);
				}
				else
				{
					e.ItemHeight = (Font.Height * 3) + (Consts.Buffer * 5);
				}
			}
		}
		
		// a row needs to be drawn
		protected override void OnDrawItem(DrawItemEventArgs e)
		{
			base.OnDrawItem(e);
			
			if (e.Index < 0 || e.Index >= Items.Count)
				return;
			
			// each section is drawn on an offscreen bitmap to prevent flickering
			// the bitmap is only created when necessary (when the row size changes)
			CreateOffscreenGraphics(e.Index);
			m_graphics.Clear(SystemColors.Window);
			
			// header is index 0, others are data items
			if (e.Index == 0)
			{
				DrawHeader(m_graphics, e.Bounds.Width, e.Bounds.Height);
			}
			else
			{
				DrawRow(m_graphics, e.Bounds.Width, e.Bounds.Height, (RowItem)this.Items[e.Index]);
			}
			
			//blit the offscreen bitmap to the screen
			e.Graphics.DrawImage(m_bmpItem, e.Bounds.Left, e.Bounds.Top, m_bmpItem.Width, m_bmpItem.Height);
		}

		// need to redraw rows when resize
		protected override void OnResize(EventArgs e)
		{
			base.OnResize(e);
			Invalidate();
		}

		// draw the header
		private void DrawHeader(Graphics g, int width, int height)
		{
			// left label
			g.DrawString("User/Comment", m_fontHeader, SystemBrushes.ControlText, Consts.Buffer, (height - m_fontHeader.Height - Consts.Buffer));
			
			if (width > Consts.DrawRightSideWidth)
			{
				g.DrawString("Task Date", m_fontHeader, SystemBrushes.ControlText, (width - Consts.RightBuffer), (height - m_fontHeader.Height - Consts.Buffer));
			}
			
			// separator
			g.DrawLine(Pens.LightGray, 0, height - 1, width, height - 1);
		}	

		// draw data item
		private void DrawRow(Graphics g, int width, int height, RowItem item)
		{
			//display name
			g.DrawString(item.DisplayName, this.Font, SystemBrushes.ControlText, Consts.Buffer, Consts.Buffer);
		
			//date created	
			if (width > Consts.DrawRightSideWidth)
			{
				g.DrawString(item.DateCreated, this.Font, Brushes.DarkGray, width - Consts.RightBuffer, Consts.Buffer);
			}
			
			//calculate the comment area
			RectangleF boundsComment = new RectangleF(Consts.Buffer, this.Font.Height + (Consts.Buffer * 3), width - (Consts.Buffer * 2), this.Font.Height * 2);
		
			//comment
			g.DrawString(item.Comment, this.Font, SystemBrushes.ControlText, boundsComment, m_format);
			
			//separator
			g.DrawLine(Pens.LightGray, 0, height - 1, width, height - 1);
		}

		// maintain an offscreen bitmap that is used to draw each 
		// item in the listbox, use the same bitmap if possible, only
		// create a new one when the size changes
		private void CreateOffscreenGraphics(int index)
		{
			if (index >= 0 && index < Items.Count)
			{
				// see if need to create the offscreen bitmap
				Rectangle bounds = GetItemRectangle(index);
				
				if (m_bmpItem == null || m_bmpItem.Width != bounds.Width || m_bmpItem.Height != bounds.Height)
				{
					// size changed, create the bitmap and graphics
					if (m_bmpItem != null)
					{
						m_bmpItem.Dispose();
					}
					
					m_bmpItem = new Bitmap(bounds.Width, bounds.Height);
					
					if (m_graphics != null)
					{
						m_graphics.Dispose();
					}
					
					m_graphics = Graphics.FromImage(m_bmpItem);
				}
			}
		}

		// paint the background part of the control that does not contain any items
		protected override void WndProc(ref Message m)
		{
			const int WM_ERASEBKGND = 20;
			
			// look for background erase message
			if (m.Msg == WM_ERASEBKGND)
			{
				// let Windows handle the message if the list is empty
				if (Items.Count > 0)
				{
					// calculate the area between the bottom of the last
					// item and the bottom of the list box control
					Rectangle rc = GetItemRectangle(Items.Count - 1);
					
					// fill in the bottom area
					if (rc.Bottom != 0 && rc.Bottom < DisplayRectangle.Bottom)
					{
						Graphics g = Graphics.FromHwnd(Handle);
						g.FillRectangle(SystemBrushes.Window, DisplayRectangle.Left, rc.Bottom, DisplayRectangle.Width, DisplayRectangle.Bottom - rc.Bottom);
						g.Dispose();
					}
				}
			}
			else
			{
				base.WndProc(ref m);
			}
		}
	}
}