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Development Platform:
C#

ColorComboBox.cs：Code Content
							using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Windows.Forms;
using System.Diagnostics;
using UtilityLibrary.Win32;
using UtilityLibrary.General;
using UtilityLibrary.Menus;
namespace UtilityLibrary.WinControls
{
	/// <summary>
	/// Summary description for ColorComboBox.
	/// </summary>
	[ToolboxItem(true)]
	[ToolboxBitmap(typeof(UtilityLibrary.WinControls.ColorComboBox), 
     "UtilityLibrary.WinControls.ColorComboBox.bmp")]
	[Designer(typeof(UtilityLibrary.Designers.ColorComboBoxDesigner))]
	public class ColorComboBox : ComboBoxBase
	{
		#region Class Variables
		private const int PREVIEW_BOX_WIDTH = 20;
		#endregion
		
		#region Constructos
		// For use when hosted by a toolbar
		public ColorComboBox(bool toolBarUse) : base(toolBarUse)
		{
			DropDownStyle = ComboBoxStyle.DropDownList;
			Items.AddRange(ColorUtil.KnownColorNames);
		}
		public ColorComboBox()
		{
			DropDownStyle = ComboBoxStyle.DropDownList;
			Items.AddRange(ColorUtil.KnownColorNames);
		}
		#endregion
        #region Overrides
		protected override void DrawComboBoxItem(Graphics g, Rectangle bounds, int Index, bool selected, bool editSel)
		{
			
			// Call base class to do the "Flat ComboBox" drawing
			base.DrawComboBoxItem(g, bounds, Index, selected, editSel);
			if ( Index != -1)
			{
				string item = Items[Index].ToString();
				Color currentColor = Color.FromName(item);
				Brush brush;
				brush = new SolidBrush(SystemColors.MenuText);
				
				Brush currentColorBrush = new SolidBrush(currentColor);
				g.FillRectangle(currentColorBrush, bounds.Left+2, bounds.Top+2, PREVIEW_BOX_WIDTH , bounds.Height-4);
				currentColorBrush.Dispose();
				Pen blackPen = new Pen(Brushes.Black, 1);
				g.DrawRectangle(blackPen, new Rectangle(bounds.Left+1, bounds.Top+1, PREVIEW_BOX_WIDTH+1, bounds.Height-3));
				blackPen.Dispose();
                Size textSize = TextUtil.GetTextSize(g, Items[Index].ToString(), Font);
				int top = bounds.Top + (bounds.Height - textSize.Height)/2;
				g.DrawString(item, Font, brush, new Point(bounds.Left + 28, top));
                brush.Dispose();
			}
		}
		protected override void DrawComboBoxItemEx(Graphics g, Rectangle bounds, int Index, bool selected, bool editSel)
		{
			
			// This "hack" is necessary to avoid a clipping bug that comes from the fact that sometimes
			// we are drawing using the Graphics object for the edit control in the combobox and sometimes
			// we are using the graphics object for the combobox itself. If we use the same function to do our custom
			// drawing it is hard to adjust for the clipping because of this situation
			base.DrawComboBoxItemEx(g, bounds, Index, selected, editSel);
			if ( Index != -1)
			{
				string item = Items[Index].ToString();
				Color currentColor = Color.FromName(item);
				SolidBrush brush;
				brush = new SolidBrush(SystemColors.MenuText);
				Rectangle rc = bounds;
				rc.Inflate(-3, -3);
				Brush currentColorBrush = new SolidBrush(currentColor);
				g.FillRectangle(currentColorBrush, rc.Left+2, rc.Top+2, PREVIEW_BOX_WIDTH , rc.Height-4);
				Pen blackPen = new Pen(Brushes.Black, 1);
				g.DrawRectangle(blackPen, new Rectangle(rc.Left+1, rc.Top+1, PREVIEW_BOX_WIDTH+1, rc.Height-3));
				blackPen.Dispose();
				Size textSize = TextUtil.GetTextSize(g, Items[Index].ToString(), Font);
				int top = bounds.Top + (bounds.Height - textSize.Height)/2;
				// Clipping rectangle
				Rectangle clipRect = new Rectangle(bounds.Left + 31, top, bounds.Width - 31 - ARROW_WIDTH - 4, top+textSize.Height);
                g.DrawString(Items[Index].ToString(), Font, brush, clipRect);
				brush.Dispose();
			
			}
		}
		
		protected override void DrawDisableState()
		{
			// Draw the combobox state disable
			base.DrawDisableState();
			
            // Draw the specific disable state to
			// this derive class
			using ( Graphics g = CreateGraphics() )
			{
				using ( Brush b = new SolidBrush(SystemColors.ControlDark) )
				{
					Rectangle rc = ClientRectangle;
					Rectangle bounds = new Rectangle(rc.Left, rc.Top, rc.Width, rc.Height);
					bounds.Inflate(-3, -3);
					g.DrawRectangle(SystemPens.ControlDark, new Rectangle(bounds.Left+2, 
						bounds.Top+2, PREVIEW_BOX_WIDTH, bounds.Height-4));
					int index = SelectedIndex;
					Size textSize = TextUtil.GetTextSize(g, Items[index].ToString(), Font);
					
					// Clipping rectangle
					int top = rc.Top + (rc.Height - textSize.Height)/2;
					Rectangle clipRect = new Rectangle(rc.Left + 31, 
						top, rc.Width - 31 - ARROW_WIDTH - 4, top+textSize.Height);
					g.DrawString(Items[index].ToString(), Font, b, clipRect);
				}
			}
		}
		#endregion
		#region Methods
		public void PassMsg(ref Message m)
		{
			base.WndProc(ref m);
		}
		#endregion
        
	}
}

						