GroupBoxRenderer.cs source code in C# .NET

                        Code:
                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / WinForms / Managed / System / WinForms / GroupBoxRenderer.cs / 1 / GroupBoxRenderer.cs
                        
                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 
namespace System.Windows.Forms {
 
using System; 
using System.Drawing;
using System.Windows.Forms.Internal; 
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Windows.Forms.VisualStyles;
using Microsoft.Win32; 

 
    ///  
    /// 
    ///     
    ///       This is a rendering class for the GroupBox control.
    ///    
    /// 
    public sealed class GroupBoxRenderer { 

        //Make this per-thread, so that different threads can safely use these methods. 
        [ThreadStatic] 
        private static VisualStyleRenderer visualStyleRenderer = null;
        private static readonly VisualStyleElement GroupBoxElement = VisualStyleElement.Button.GroupBox.Normal; 
        private const int textOffset = 8;        //MAGIC NUMBER - WHERE DID IT COME FROM?
        private const int boxHeaderWidth = 7;    // VSWhidbey 514912: The groupbox frame shows 7 pixels before the caption.
        private static bool renderMatchingApplicationState = true;
        //cannot instantiate 
        private GroupBoxRenderer() {
        } 
 
        /// 
        ///  
        ///    
        ///      If this property is true, then the renderer will use the setting from Application.RenderWithVisualStyles to
        /// determine how to render.
        ///      If this property is false, the renderer will always render with visualstyles. 
        ///    
        ///  
        public static bool RenderMatchingApplicationState { 
            get {
                return renderMatchingApplicationState; 
            }
            set {
                renderMatchingApplicationState = value;
            } 
        }
 
        private static bool RenderWithVisualStyles { 
            get {
                return (!renderMatchingApplicationState || Application.RenderWithVisualStyles); 
            }
        }

        ///  
        /// 
        ///     
        ///       Returns true if the background corresponding to the given state is partially transparent, else false. 
        ///    
        ///  
        public static bool IsBackgroundPartiallyTransparent(GroupBoxState state) {
           if (RenderWithVisualStyles) {
               InitializeRenderer((int)state);
               return visualStyleRenderer.IsBackgroundPartiallyTransparent(); 
           }
           else { 
               return false; //for downlevel, this is false 
           }
        } 

        /// 
        /// 
        ///     
        ///       This is just a convenience wrapper for VisualStyleRenderer.DrawThemeParentBackground. For downlevel,
        ///       this isn't required and does nothing. 
        ///     
        /// 
        [ 
            SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters") // Using Graphics instead of IDeviceContext intentionally
        ]
        public static void DrawParentBackground(Graphics g, Rectangle bounds, Control childControl) {
           if (RenderWithVisualStyles) { 
               InitializeRenderer(0);
               visualStyleRenderer.DrawParentBackground(g, bounds, childControl); 
           } 
        }
 
        /// 
        /// 
        ///    
        ///       Renders a GroupBox control. 
        ///    
        ///  
        public static void DrawGroupBox(Graphics g, Rectangle bounds, GroupBoxState state) { 
            if (RenderWithVisualStyles)
                DrawThemedGroupBoxNoText(g, bounds, state); 
            else
                DrawUnthemedGroupBoxNoText(g, bounds, state);
        }
 
        /// 
        ///  
        ///     
        ///       Renders a GroupBox control. Uses the text color specified by the theme.
        ///     
        /// 
        public static void DrawGroupBox(Graphics g, Rectangle bounds, string groupBoxText, Font font, GroupBoxState state) {
            DrawGroupBox(g, bounds, groupBoxText, font, TextFormatFlags.Top | TextFormatFlags.Left, state);
        } 

        ///  
        ///  
        ///    
        ///       Renders a GroupBox control. 
        ///    
        /// 
        public static void DrawGroupBox(Graphics g, Rectangle bounds, string groupBoxText, Font font, Color textColor, GroupBoxState state) {
            DrawGroupBox(g, bounds, groupBoxText, font, textColor, TextFormatFlags.Top | TextFormatFlags.Left, state); 
        }
 
        ///  
        /// 
        ///     
        ///       Renders a GroupBox control. Uses the text color specified by the theme.
        ///    
        /// 
        public static void DrawGroupBox(Graphics g, Rectangle bounds, string groupBoxText, Font font, TextFormatFlags flags, GroupBoxState state) { 
            if (RenderWithVisualStyles)
                DrawThemedGroupBoxWithText(g, bounds, groupBoxText, font, DefaultTextColor(state), flags, state); 
            else 
                DrawUnthemedGroupBoxWithText(g, bounds, groupBoxText, font, DefaultTextColor(state), flags, state);
        } 

        /// 
        /// 
        ///     
        ///       Renders a GroupBox control.
        ///     
        ///  
        public static void DrawGroupBox(Graphics g, Rectangle bounds, string groupBoxText, Font font, Color textColor, TextFormatFlags flags, GroupBoxState state) {
            if (RenderWithVisualStyles) 
                DrawThemedGroupBoxWithText(g, bounds, groupBoxText, font, textColor, flags, state);
            else
                DrawUnthemedGroupBoxWithText(g, bounds, groupBoxText, font, textColor, flags, state);
        } 

        ///  
        ///     Draws a themed GroupBox with no text label. 
        /// 
        ///  
        private static void DrawThemedGroupBoxNoText(Graphics g, Rectangle bounds, GroupBoxState state) {
            InitializeRenderer((int)state);
            visualStyleRenderer.DrawBackground(g, bounds);
        } 

        ///  
        ///     Draws a themed GroupBox with a text label. 
        /// 
        ///  
        private static void DrawThemedGroupBoxWithText(Graphics g, Rectangle bounds, string groupBoxText, Font font, Color textColor, TextFormatFlags flags, GroupBoxState state) {
            InitializeRenderer((int)state);

            // Calculate text area, and render text inside it 
            Rectangle textBounds = bounds;
 
            textBounds.Width -= 2 * boxHeaderWidth; 
            Size measuredBounds = TextRenderer.MeasureText(g, groupBoxText, font, new Size(textBounds.Width, textBounds.Height), flags);
            textBounds.Width = measuredBounds.Width; 
            textBounds.Height = measuredBounds.Height;

            if ((flags & TextFormatFlags.Right) == TextFormatFlags.Right) {
                textBounds.X = bounds.Right - textBounds.Width - boxHeaderWidth + 1;  // +1 to account for the margin built in the MeasureText result 
            }
            else { 
                textBounds.X += boxHeaderWidth - 1;                                   // -1 to account for the margin built in the MeasureText result 
            }
 
            TextRenderer.DrawText(g, groupBoxText, font, textBounds, textColor, flags);

            // Calculate area for background box
            Rectangle boxBounds = bounds; 
            boxBounds.Y += font.Height / 2;
            boxBounds.Height -= font.Height / 2; 
 
            // Break box into three segments, that don't overlap the text area
            Rectangle clipLeft   = boxBounds; 
            Rectangle clipMiddle = boxBounds;
            Rectangle clipRight  = boxBounds;

            clipLeft.Width = boxHeaderWidth; 
            clipMiddle.Width = Math.Max(0, textBounds.Width - 3);  // -3 to account for the margin built in the MeasureText result
            if ((flags & TextFormatFlags.Right) == TextFormatFlags.Right) 
            { 
                clipLeft.X = boxBounds.Right - boxHeaderWidth;
                clipMiddle.X = clipLeft.Left - clipMiddle.Width; 
                clipRight.Width = clipMiddle.X - boxBounds.X;
            }
            else
            { 
                clipMiddle.X = clipLeft.Right;
                clipRight.X = clipMiddle.Right; 
                clipRight.Width = boxBounds.Right - clipRight.X; 
            }
            clipMiddle.Y = textBounds.Bottom; 
            clipMiddle.Height -= (textBounds.Bottom - boxBounds.Top);

            Debug.Assert(textBounds.Y <= boxBounds.Y, "if text below box, need to render area of box above text");
 
            // Render clipped portion of background in each segment
            visualStyleRenderer.DrawBackground(g, boxBounds, clipLeft); 
            visualStyleRenderer.DrawBackground(g, boxBounds, clipMiddle); 
            visualStyleRenderer.DrawBackground(g, boxBounds, clipRight);
        } 

        /// 
        ///     Draws an un-themed GroupBox with no text label.
        ///  
        /// 
        private static void DrawUnthemedGroupBoxNoText(Graphics g, Rectangle bounds, GroupBoxState state) { 
            Color backColor = SystemColors.Control; 
            Pen light = new Pen(ControlPaint.Light(backColor, 1.0f));
            Pen dark = new Pen(ControlPaint.Dark(backColor, 0f)); 
            try {
                // left
                g.DrawLine(light, bounds.Left + 1, bounds.Top + 1, bounds.Left + 1, bounds.Height - 1);
                g.DrawLine(dark, bounds.Left, bounds.Top + 1, bounds.Left, bounds.Height - 2); 

                // bottom 
                g.DrawLine(light, bounds.Left, bounds.Height - 1, bounds.Width - 1, bounds.Height - 1); 
                g.DrawLine(dark, bounds.Left, bounds.Height - 2, bounds.Width - 1, bounds.Height - 2);
 
                // top
                g.DrawLine(light, bounds.Left + 1, bounds.Top + 1, bounds.Width - 1, bounds.Top + 1);
                g.DrawLine(dark, bounds.Left, bounds.Top, bounds.Width - 2, bounds.Top);
 
                // right
                g.DrawLine(light, bounds.Width - 1, bounds.Top, bounds.Width - 1, bounds.Height - 1); 
                g.DrawLine(dark, bounds.Width - 2, bounds.Top, bounds.Width - 2, bounds.Height - 2); 
            }
            finally { 
                if (light != null) {
                    light.Dispose();
                }
                if (dark != null) { 
                    dark.Dispose();
                } 
            } 
        }
 
        /// 
        ///     Draws an un-themed GroupBox with a text label.
        ///     Variation of the logic in GroupBox.DrawGroupBox().
        ///  
        /// 
        private static void DrawUnthemedGroupBoxWithText(Graphics g, Rectangle bounds, string groupBoxText, Font font, Color textColor, TextFormatFlags flags, GroupBoxState state) { 
            // Calculate text area, and render text inside it 
            Rectangle textBounds = bounds;
 
            textBounds.Width -= textOffset;
            Size measuredBounds = TextRenderer.MeasureText(g, groupBoxText, font, new Size(textBounds.Width, textBounds.Height), flags);
            textBounds.Width = measuredBounds.Width;
            textBounds.Height = measuredBounds.Height; 

            if ((flags & TextFormatFlags.Right) == TextFormatFlags.Right) { 
                textBounds.X = bounds.Right - textBounds.Width - textOffset; 
            }
            else { 
                textBounds.X += textOffset;
            }

            TextRenderer.DrawText(g, groupBoxText, font, textBounds, textColor, flags); 

            // Pad text area to stop background from touching text 
            if (textBounds.Width > 0) 
                textBounds.Inflate(2, 0);
 
            Pen light = new Pen(SystemColors.ControlLight);
            Pen dark = new Pen(SystemColors.ControlDark);

            int boxTop = bounds.Top + font.Height / 2; 

            // left 
            g.DrawLine(light, bounds.Left + 1, boxTop, bounds.Left + 1, bounds.Height - 1); 
            g.DrawLine(dark, bounds.Left, boxTop - 1, bounds.Left, bounds.Height - 2);
 
            // bottom
            g.DrawLine(light, bounds.Left, bounds.Height - 1, bounds.Width, bounds.Height - 1);
            g.DrawLine(dark, bounds.Left, bounds.Height - 2, bounds.Width - 1, bounds.Height - 2);
 
            // top-left
            g.DrawLine(light, bounds.Left + 1, boxTop, textBounds.X - 2, boxTop); 
            g.DrawLine(dark, bounds.Left, boxTop - 1, textBounds.X - 3, boxTop - 1); 

            // top-right 
            g.DrawLine(light, textBounds.X + textBounds.Width + 1, boxTop, bounds.Width - 1, boxTop);
            g.DrawLine(dark, textBounds.X + textBounds.Width + 2, boxTop - 1, bounds.Width - 2, boxTop - 1);

            // right 
            g.DrawLine(light, bounds.Width - 1, boxTop, bounds.Width - 1, bounds.Height - 1);
            g.DrawLine(dark, bounds.Width - 2, boxTop - 1, bounds.Width - 2, bounds.Height - 2); 
        } 

        private static Color DefaultTextColor(GroupBoxState state) { 
            if (RenderWithVisualStyles) {
                InitializeRenderer((int)state);
                return visualStyleRenderer.GetColor(ColorProperty.TextColor);
            } 
            else {
                return SystemColors.ControlText; 
            } 
        }
 
        private static void InitializeRenderer(int state) {
           if (visualStyleRenderer == null) {
               visualStyleRenderer = new VisualStyleRenderer(GroupBoxElement.ClassName, GroupBoxElement.Part, state);
           } 
           else {
               visualStyleRenderer.SetParameters(GroupBoxElement.ClassName, GroupBoxElement.Part, state); 
           } 
       }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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