GroupBox.cs

using System;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace Cyotek.Windows.Forms
{
	// Cyotek GroupBox Component
	// www.cyotek.com

	/// <summary>
	/// Represents a Windows control that displays a frame at the top of a group of controls with an optional caption and icon.
	/// </summary>
	[ToolboxItem(true)]
	[DefaultEvent("Click")]
	[DefaultProperty("Text")]
	[Designer("System.Windows.Forms.Design.GroupBoxDesigner, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
	[Designer("System.Windows.Forms.Design.DocumentDesigner, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", typeof(IRootDesigner))]
	internal class GroupBox : System.Windows.Forms.GroupBox
	{
		#region Instance Fields

		private Border3DSide _borders = Border3DSide.Top;

		private Pen _bottomPen;

		private Color _headerForeColor;

		private Size _iconMargin;

		private Image _image;

		private Color _lineColorBottom;

		private Color _lineColorTop;

		private bool _showBorders;

		private Pen _topPen;

		#endregion

		#region Public Constructors

		/// <summary>
		/// Initializes a new instance of the <see cref="GroupBox"/> class.
		/// </summary>
		public GroupBox()
		{
			_showBorders = true;
			_iconMargin = new Size(0, 6);
			_lineColorBottom = SystemColors.ButtonHighlight;
			_lineColorTop = SystemColors.ButtonShadow;
			_headerForeColor = SystemColors.HotTrack;

			SetStyle(ControlStyles.DoubleBuffer | ControlStyles.AllPaintingInWmPaint | ControlStyles.ResizeRedraw | ControlStyles.UserPaint | ControlStyles.SupportsTransparentBackColor, true);

			CreateResources();
		}

		#endregion

		#region Overridden Properties

		/// <summary>
		/// Gets a rectangle that represents the dimensions of the <see cref="T:System.Windows.Forms.GroupBox"/>.
		/// </summary>
		/// <value></value>
		/// <returns>
		/// A <see cref="T:System.Drawing.Rectangle"/> with the dimensions of the <see cref="T:System.Windows.Forms.GroupBox"/>.
		/// </returns>
		public override Rectangle DisplayRectangle
		{
			get
			{
				Size clientSize;
				int fontHeight;
				int imageSize;

				clientSize = base.ClientSize;
				fontHeight = Font.Height;

				if (_image != null)
				{
					imageSize = _iconMargin.Width + _image.Width + 3;
				}
				else
				{
					imageSize = 0;
				}

				return new Rectangle(3 + imageSize, fontHeight + 3, Math.Max(clientSize.Width - (imageSize + 6), 0), Math.Max(clientSize.Height - fontHeight - 6, 0));
			}
		}

		/// <summary>
		/// Returns or sets the text displayed in this control.
		/// </summary>
		/// <value></value>
		/// <returns>
		/// The text associated with this control.
		/// </returns>
		[Browsable(true)]
		[DefaultValue("")]
		public override string Text
		{
			get { return base.Text; }
			set
			{
				base.Text = value;
				Invalidate();
			}
		}

		#endregion

		#region Overridden Methods

		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
		protected override void Dispose(bool disposing)
		{
			if (disposing)
			{
				CleanUpResources();
			}

			base.Dispose(disposing);
		}

		/// <summary>
		/// Occurs when the control is to be painted.
		/// </summary>
		/// <param name="e">A <see cref="T:System.Windows.Forms.PaintEventArgs"/> that contains the event data.</param>
		protected override void OnPaint(PaintEventArgs e)
		{
			SizeF size;
			int y;
			TextFormatFlags flags;
			Rectangle textBounds;

			flags = TextFormatFlags.WordEllipsis | TextFormatFlags.NoPrefix | TextFormatFlags.Left | TextFormatFlags.SingleLine;

			size = TextRenderer.MeasureText(e.Graphics, Text, Font, ClientSize, flags);
			y = (int)(size.Height + 3) / 2;
			textBounds = new Rectangle(1, 1, (int)size.Width, (int)size.Height);

			if (ShowBorders)
			{
				if ((_borders & Border3DSide.All) == Border3DSide.All)
				{
					e.Graphics.DrawRectangle(_bottomPen, 1, y + 1, Width - 2, Height - (y + 2));
					e.Graphics.DrawRectangle(_topPen, 0, y, Width - 2, Height - (y + 2));
				}
				else
				{
					if ((_borders & Border3DSide.Top) == Border3DSide.Top)
					{
						e.Graphics.DrawLine(_topPen, size.Width + 3, y, Width - 5, y);
						e.Graphics.DrawLine(_bottomPen, size.Width + 3, y + 1, Width - 5, y + 1);
					}

					if ((_borders & Border3DSide.Left) == Border3DSide.Left)
					{
						e.Graphics.DrawLine(_topPen, 0, y, 0, Height - 1);
						e.Graphics.DrawLine(_bottomPen, 1, y, 1, Height - 1);
					}

					if ((_borders & Border3DSide.Right) == Border3DSide.Right)
					{
						e.Graphics.DrawLine(_bottomPen, Width - 1, y, Width - 1, Height - 1);
						e.Graphics.DrawLine(_topPen, Width - 2, y, Width - 2, Height - 1);
					}

					if ((_borders & Border3DSide.Bottom) == Border3DSide.Bottom)
					{
						e.Graphics.DrawLine(_topPen, 0, Height - 2, Width, Height - 2);
						e.Graphics.DrawLine(_bottomPen, 0, Height - 1, Width, Height - 1);
					}
				}
			}

			// header text
			TextRenderer.DrawText(e.Graphics, Text, Font, textBounds, HeaderForeColor, flags);

			// draw the image
			if ((_image != null))
			{
				e.Graphics.DrawImage(_image, Padding.Left + _iconMargin.Width, Padding.Top + (int)size.Height + _iconMargin.Height, _image.Width, _image.Height);
			}

			//draw a designtime outline
			if (DesignMode && (_borders & Border3DSide.All) != Border3DSide.All)
			{
				using var pen = new Pen(SystemColors.ButtonShadow);
				pen.DashStyle = DashStyle.Dot;
				e.Graphics.DrawRectangle(pen, 0, 0, Width - 1, Height - 1);
			}
		}

		/// <summary>
		/// Raises the <see cref="System.Windows.Forms.Control.SystemColorsChanged"/> event.
		/// </summary>
		/// <param name="e">An <see cref="T:System.EventArgs"/> that contains the event data.</param>
		protected override void OnSystemColorsChanged(EventArgs e)
		{
			base.OnSystemColorsChanged(e);

			CreateResources();
			Invalidate();
		}

		#endregion

		#region Public Properties

		[Category("Appearance")]
		[DefaultValue(typeof(Border3DSide), "Top")]
		public Border3DSide Borders
		{
			get { return _borders; }
			set
			{
				_borders = value;
				Invalidate();
			}
		}

		[Category("Appearance")]
		[DefaultValue(typeof(Color), "HotTrack")]
		public Color HeaderForeColor
		{
			get { return _headerForeColor; }
			set
			{
				_headerForeColor = value;
				CreateResources();
				Invalidate();
			}
		}

		/// <summary>
		/// Gets or sets the icon margin.
		/// </summary>
		/// <value>The icon margin.</value>
		[Category("Appearance")]
		[DefaultValue(typeof(Size), "0, 6")]
		public Size IconMargin
		{
			get { return _iconMargin; }
			set
			{
				_iconMargin = value;
				Invalidate();
			}
		}

		/// <summary>
		/// Gets or sets the image to display.
		/// </summary>
		/// <value>The image to display.</value>
		[Browsable(true)]
		[Category("Appearance")]
		[DefaultValue(typeof(Image), "")]
		public Image Image
		{
			get { return _image; }
			set
			{
				_image = value;
				Invalidate();
			}
		}

		/// <summary>
		/// Gets or sets the line color bottom.
		/// </summary>
		/// <value>The line color bottom.</value>
		[Browsable(true)]
		[Category("Appearance")]
		[DefaultValue(typeof(Color), "ButtonHighlight")]
		public Color LineColorBottom
		{
			get { return _lineColorBottom; }
			set
			{
				_lineColorBottom = value;
				CreateResources();
				Invalidate();
			}
		}

		/// <summary>
		/// Gets or sets the line color top.
		/// </summary>
		/// <value>The line color top.</value>
		[Browsable(true)]
		[Category("Appearance")]
		[DefaultValue(typeof(Color), "ButtonShadow")]
		public Color LineColorTop
		{
			get { return _lineColorTop; }
			set
			{
				_lineColorTop = value;
				CreateResources();
				Invalidate();
			}
		}

		[DefaultValue(true)]
		[Category("Appearance")]
		public bool ShowBorders
		{
			get { return _showBorders; }
			set
			{
				_showBorders = value;
				Invalidate();
			}
		}

		#endregion

		#region Private Members

		/// <summary>
		/// Cleans up GDI resources.
		/// </summary>
		private void CleanUpResources()
		{
			if (_topPen != null)
			{
				_topPen.Dispose();
			}

			if (_bottomPen != null)
			{
				_bottomPen.Dispose();
			}
		}

		/// <summary>
		/// Creates GDI resources.
		/// </summary>
		private void CreateResources()
		{
			CleanUpResources();

			_topPen = new Pen(_lineColorTop);
			_bottomPen = new Pen(_lineColorBottom);
		}

		#endregion
	}
}