Class for native GDI text rendering (http://theartofdev.com/2013/08/12/using-native-gdi-for-text-rendering-in-c/)

NativeTextRenderer.cs

/// <summary>
/// Wrapper for GDI text rendering functions<br/>
/// This class is not thread-safe as GDI function should be called from the UI thread.
/// </summary>
/// <remarks>
/// http://theartofdev.com/2013/08/12/using-native-gdi-for-text-rendering-in-c/<br/>
/// The MIT License (MIT) Copyright (c) 2014 Arthur Teplitzki.
/// </remarks>
public sealed class NativeTextRenderer : IDisposable
{
    #region Fields and Consts
 
    /// <summary>
    /// used for <see cref="MeasureString(string,System.Drawing.Font,float,out int,out int)"/> calculation.
    /// </summary>
    private static readonly int[] _charFit = new int[1];
 
    /// <summary>
    /// used for <see cref="MeasureString(string,System.Drawing.Font,float,out int,out int)"/> calculation.
    /// </summary>
    private static readonly int[] _charFitWidth = new int[1000];
 
    /// <summary>
    /// cache of all the font used not to create same font again and again
    /// </summary>
    private static readonly Dictionary<string, Dictionary<float, Dictionary<FontStyle, IntPtr>>> _fontsCache = new Dictionary<string, Dictionary<float, Dictionary<FontStyle, IntPtr>>>(StringComparer.InvariantCultureIgnoreCase);
 
    /// <summary>
    /// The wrapped WinForms graphics object
    /// </summary>
    private readonly Graphics _g;
 
    /// <summary>
    /// the initialized HDC used
    /// </summary>
    private IntPtr _hdc;
 
    #endregion
 
 
    /// <summary>
    /// Init.
    /// </summary>
    public NativeTextRenderer(Graphics g)
    {
        _g = g;
 
        var clip = _g.Clip.GetHrgn(_g);
 
        _hdc = _g.GetHdc();
        SetBkMode(_hdc, 1);
 
        SelectClipRgn(_hdc, clip);
 
        DeleteObject(clip);
    }
 
    /// <summary>
    /// Measure the width and height of string <paramref name="str"/> when drawn on device context HDC
    /// using the given font <paramref name="font"/>.
    /// </summary>
    /// <param name="str">the string to measure</param>
    /// <param name="font">the font to measure string with</param>
    /// <returns>the size of the string</returns>
    public Size MeasureString(string str, Font font)
    {
        SetFont(font);
 
        var size = new Size();
        GetTextExtentPoint32(_hdc, str, str.Length, ref size);
        return size;
    }
 
    /// <summary>
    /// Measure the width and height of string <paramref name="str"/> when drawn on device context HDC
    /// using the given font <paramref name="font"/>.<br/>
    /// Restrict the width of the string and get the number of characters able to fit in the restriction and
    /// the width those characters take.
    /// </summary>
    /// <param name="str">the string to measure</param>
    /// <param name="font">the font to measure string with</param>
    /// <param name="maxWidth">the max width to render the string in</param>
    /// <param name="charFit">the number of characters that will fit under <see cref="maxWidth"/> restriction</param>
    /// <param name="charFitWidth"></param>
    /// <returns>the size of the string</returns>
    public Size MeasureString(string str, Font font, float maxWidth, out int charFit, out int charFitWidth)
    {
        SetFont(font);
 
        var size = new Size();
        GetTextExtentExPoint(_hdc, str, str.Length, (int)Math.Round(maxWidth), _charFit, _charFitWidth, ref size);
        charFit = _charFit[0];
        charFitWidth = charFit > 0 ? _charFitWidth[charFit - 1] : 0;
        return size;
    }
 
    /// <summary>
    /// Draw the given string using the given font and foreground color at given location.
    /// </summary>
    /// <param name="str">the string to draw</param>
    /// <param name="font">the font to use to draw the string</param>
    /// <param name="color">the text color to set</param>
    /// <param name="point">the location to start string draw (top-left)</param>
    public void DrawString(String str, Font font, Color color, Point point)
    {
        SetFont(font);
        SetTextColor(color);
 
        TextOut(_hdc, point.X, point.Y, str, str.Length);
    }
 
    /// <summary>
    /// Draw the given string using the given font and foreground color at given location.<br/>
    /// See http://msdn.microsoft.com/en-us/library/windows/desktop/dd162498(v=vs.85).aspx.
    /// </summary>
    /// <param name="str">the string to draw</param>
    /// <param name="font">the font to use to draw the string</param>
    /// <param name="color">the text color to set</param>
    /// <param name="rect">the rectangle in which the text is to be formatted</param>
    /// <param name="flags">The method of formatting the text</param>
    public void DrawString(String str, Font font, Color color, Rectangle rect, TextFormatFlags flags)
    {
        SetFont(font);
        SetTextColor(color);
 
        var rect2 = new Rect(rect);
        DrawText(_hdc, str, str.Length, ref rect2, (uint)flags);
    }
 
    /// <summary>
    /// Special draw logic to draw transparent text using GDI.<br/>
    /// 1. Create in-memory DC<br/>
    /// 2. Copy background to in-memory DC<br/>
    /// 3. Draw the text to in-memory DC<br/>
    /// 4. Copy the in-memory DC to the proper location with alpha blend<br/>
    /// </summary>
    public void DrawTransparentText(string str, Font font, Color color, Point point, Size size)
    {
        // Create a memory DC so we can work off-screen
        IntPtr memoryHdc = CreateCompatibleDC(_hdc);
        SetBkMode(memoryHdc, 1);
 
        // Create a device-independent bitmap and select it into our DC
        var info = new BitMapInfo();
        info.biSize = Marshal.SizeOf(info);
        info.biWidth = size.Width;
        info.biHeight = -size.Height;
        info.biPlanes = 1;
        info.biBitCount = 32;
        info.biCompression = 0; // BI_RGB
        IntPtr ppvBits;
        IntPtr dib = CreateDIBSection(_hdc, ref info, 0, out ppvBits, IntPtr.Zero, 0);
        SelectObject(memoryHdc, dib);
 
        try
        {
            // copy target background to memory HDC so when copied back it will have the proper background
            BitBlt(memoryHdc, 0, 0, size.Width, size.Height, _hdc, point.X, point.Y, 0x00CC0020);
 
            // Create and select font
            SelectObject(memoryHdc, GetCachedHFont(font));
            SetTextColor(memoryHdc, (color.B & 0xFF) << 16 | (color.G & 0xFF) << 8 | color.R);
 
            // Draw text to memory HDC
            TextOut(memoryHdc, 0, 0, str, str.Length);
 
            // copy from memory HDC to normal HDC with alpha blend so achieve the transparent text
            AlphaBlend(_hdc, point.X, point.Y, size.Width, size.Height, memoryHdc, 0, 0, size.Width, size.Height, new BlendFunction(color.A));
        }
        finally
        {
            DeleteObject(dib);
            DeleteDC(memoryHdc);
        }
    }
 
    /// <summary>
    /// Release current HDC to be able to use <see cref="Graphics"/> methods.
    /// </summary>
    public void Dispose()
    {
        if (_hdc != IntPtr.Zero)
        {
            SelectClipRgn(_hdc, IntPtr.Zero);
            _g.ReleaseHdc(_hdc);
            _hdc = IntPtr.Zero;
        }
    }
 
 
    #region Private methods
 
    /// <summary>
    /// Set a resource (e.g. a font) for the specified device context.
    /// </summary>
    private void SetFont(Font font)
    {
        SelectObject(_hdc, GetCachedHFont(font));
    }
 
    /// <summary>
    /// Get cached unmanaged font handle for given font.<br/>
    /// </summary>
    /// <param name="font">the font to get unmanaged font handle for</param>
    /// <returns>handle to unmanaged font</returns>
    private static IntPtr GetCachedHFont(Font font)
    {
        IntPtr hfont = IntPtr.Zero;
        Dictionary<float, Dictionary<FontStyle, IntPtr>> dic1;
        if (_fontsCache.TryGetValue(font.Name, out dic1))
        {
            Dictionary<FontStyle, IntPtr> dic2;
            if (dic1.TryGetValue(font.Size, out dic2))
            {
                dic2.TryGetValue(font.Style, out hfont);
            }
            else
            {
                dic1[font.Size] = new Dictionary<FontStyle, IntPtr>();
            }
        }
        else
        {
            _fontsCache[font.Name] = new Dictionary<float, Dictionary<FontStyle, IntPtr>>();
            _fontsCache[font.Name][font.Size] = new Dictionary<FontStyle, IntPtr>();
        }
 
        if (hfont == IntPtr.Zero)
        {
            _fontsCache[font.Name][font.Size][font.Style] = hfont = font.ToHfont();
        }
 
        return hfont;
    }
 
    /// <summary>
    /// Set the text color of the device context.
    /// </summary>
    private void SetTextColor(Color color)
    {
        int rgb = (color.B & 0xFF) << 16 | (color.G & 0xFF) << 8 | color.R;
        SetTextColor(_hdc, rgb);
    }
 
    [DllImport("gdi32.dll")]
    private static extern int SetBkMode(IntPtr hdc, int mode);
 
    [DllImport("gdi32.dll")]
    private static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiObj);
 
    [DllImport("gdi32.dll")]
    private static extern int SetTextColor(IntPtr hdc, int color);
 
    [DllImport("gdi32.dll", EntryPoint = "GetTextExtentPoint32W")]
    private static extern int GetTextExtentPoint32(IntPtr hdc, [MarshalAs(UnmanagedType.LPWStr)] string str, int len, ref Size size);
 
    [DllImport("gdi32.dll", EntryPoint = "GetTextExtentExPointW")]
    private static extern bool GetTextExtentExPoint(IntPtr hDc, [MarshalAs(UnmanagedType.LPWStr)]string str, int nLength, int nMaxExtent, int[] lpnFit, int[] alpDx, ref Size size);
 
    [DllImport("gdi32.dll", EntryPoint = "TextOutW")]
    private static extern bool TextOut(IntPtr hdc, int x, int y, [MarshalAs(UnmanagedType.LPWStr)] string str, int len);
 
    [DllImport("user32.dll", EntryPoint = "DrawTextW")]
    private static extern int DrawText(IntPtr hdc, [MarshalAs(UnmanagedType.LPWStr)] string str, int len, ref Rect rect, uint uFormat);
 
    [DllImport("gdi32.dll")]
    private static extern int SelectClipRgn(IntPtr hdc, IntPtr hrgn);
 
    [DllImport("gdi32.dll")]
    private static extern bool DeleteObject(IntPtr hObject);
 
    [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
    public static extern bool DeleteDC(IntPtr hdc);
 
    [DllImport("gdi32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, uint dwRop);
 
    [DllImport("gdi32.dll", EntryPoint = "GdiAlphaBlend")]
    private static extern bool AlphaBlend(IntPtr hdcDest, int nXOriginDest, int nYOriginDest, int nWidthDest, int nHeightDest, IntPtr hdcSrc, int nXOriginSrc, int nYOriginSrc, int nWidthSrc, int nHeightSrc, BlendFunction blendFunction);
 
    [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
    private static extern IntPtr CreateCompatibleDC(IntPtr hdc);
 
    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateDIBSection(IntPtr hdc, [In] ref BitMapInfo pbmi, uint iUsage, out IntPtr ppvBits, IntPtr hSection, uint dwOffset);
 
    // ReSharper disable NotAccessedField.Local
    // ReSharper disable MemberCanBePrivate.Local
    // ReSharper disable FieldCanBeMadeReadOnly.Local
    private struct Rect
    {
        private int _left;
        private int _top;
        private int _right;
        private int _bottom;
 
        public Rect(Rectangle r)
        {
            _left = r.Left;
            _top = r.Top;
            _bottom = r.Bottom;
            _right = r.Right;
        }
    }
 
 
    [StructLayout(LayoutKind.Sequential)]
    private struct BlendFunction
    {
        public byte BlendOp;
        public byte BlendFlags;
        public byte SourceConstantAlpha;
        public byte AlphaFormat;
 
        public BlendFunction(byte alpha)
        {
            BlendOp = 0;
            BlendFlags = 0;
            AlphaFormat = 0;
            SourceConstantAlpha = alpha;
        }
    }
 
    [StructLayout(LayoutKind.Sequential)]
    public struct BitMapInfo
    {
        public int biSize;
        public int biWidth;
        public int biHeight;
        public short biPlanes;
        public short biBitCount;
        public int biCompression;
        public int biSizeImage;
        public int biXPelsPerMeter;
        public int biYPelsPerMeter;
        public int biClrUsed;
        public int biClrImportant;
        public byte bmiColors_rgbBlue;
        public byte bmiColors_rgbGreen;
        public byte bmiColors_rgbRed;
        public byte bmiColors_rgbReserved;
    }
 
    #endregion
}
 
/// <summary>
/// See http://msdn.microsoft.com/en-us/library/windows/desktop/dd162498(v=vs.85).aspx
/// </summary>
[Flags]
public enum TextFormatFlags : uint
{
    Default = 0x00000000,
    Center = 0x00000001,
    Right = 0x00000002,
    VCenter = 0x00000004,
    Bottom = 0x00000008,
    WordBreak = 0x00000010,
    SingleLine = 0x00000020,
    ExpandTabs = 0x00000040,
    TabStop = 0x00000080,
    NoClip = 0x00000100,
    ExternalLeading = 0x00000200,
    CalcRect = 0x00000400,
    NoPrefix = 0x00000800,
    Internal = 0x00001000,
    EditControl = 0x00002000,
    PathEllipsis = 0x00004000,
    EndEllipsis = 0x00008000,
    ModifyString = 0x00010000,
    RtlReading = 0x00020000,
    WordEllipsis = 0x00040000,
    NoFullWidthCharBreak = 0x00080000,
    HidePrefix = 0x00100000,
    ProfixOnly = 0x00200000,
}