Reset RTF formatting in a WinForms RichTextBox without discarding its text?

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Saddly I’ve done my VERY best effort to slim this down to only the required code. It’s still big, but it will work. The RichTextBox api in .Net is very limited, to do anything you almost have to thunk into the Win32 library. I’ve built a entire library around this thing just so I can toggle bold and determine if bold is actually set across the selection.

Usage:

RichTextBox te = ...;
te.ClearAllFormatting(new Font("Microsoft Sans Serif", 8.25f));

Tons of code:

static class RichTextExtensions
{
    public static void ClearAllFormatting(this RichTextBox te, Font font)
    {
        CHARFORMAT2 fmt = new CHARFORMAT2();

        fmt.cbSize = Marshal.SizeOf(fmt);
        fmt.dwMask = CFM_ALL2;
        fmt.dwEffects = CFE_AUTOCOLOR | CFE_AUTOBACKCOLOR;
        fmt.szFaceName = font.FontFamily.Name;

        double size = font.Size;
        size /= 72;//logical dpi (pixels per inch)
        size *= 1440.0;//twips per inch

        fmt.yHeight = (int)size;//165
        fmt.yOffset = 0;
        fmt.crTextColor = 0;
        fmt.bCharSet = 1;// DEFAULT_CHARSET;
        fmt.bPitchAndFamily = 0;// DEFAULT_PITCH;
        fmt.wWeight = 400;// FW_NORMAL;
        fmt.sSpacing = 0;
        fmt.crBackColor = 0;
        //fmt.lcid = ???
        fmt.dwMask &= ~CFM_LCID;//don't know how to get this...
        fmt.dwReserved = 0;
        fmt.sStyle = 0;
        fmt.wKerning = 0;
        fmt.bUnderlineType = 0;
        fmt.bAnimation = 0;
        fmt.bRevAuthor = 0;
        fmt.bReserved1 = 0;

        SendMessage(te.Handle, EM_SETCHARFORMAT, SCF_ALL, ref fmt);
    }

    private const UInt32 WM_USER = 0x0400;
    private const UInt32 EM_GETCHARFORMAT = (WM_USER + 58);
    private const UInt32 EM_SETCHARFORMAT = (WM_USER + 68);
    private const UInt32 SCF_ALL = 0x0004;
    private const UInt32 SCF_SELECTION = 0x0001;

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)]
    static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, UInt32 wParam, ref CHARFORMAT2 lParam);

    [StructLayout(LayoutKind.Sequential, Pack = 4, CharSet = CharSet.Auto)]
    struct CHARFORMAT2
    {
        public int cbSize;
        public uint dwMask;
        public uint dwEffects;
        public int yHeight;
        public int yOffset;
        public int crTextColor;
        public byte bCharSet;
        public byte bPitchAndFamily;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
        public string szFaceName;
        public short wWeight;
        public short sSpacing;
        public int crBackColor;
        public int lcid;
        public int dwReserved;
        public short sStyle;
        public short wKerning;
        public byte bUnderlineType;
        public byte bAnimation;
        public byte bRevAuthor;
        public byte bReserved1;
    }

    #region CFE_
    // CHARFORMAT effects 
    const UInt32 CFE_BOLD = 0x0001;
    const UInt32 CFE_ITALIC = 0x0002;
    const UInt32 CFE_UNDERLINE = 0x0004;
    const UInt32 CFE_STRIKEOUT = 0x0008;
    const UInt32 CFE_PROTECTED = 0x0010;
    const UInt32 CFE_LINK = 0x0020;
    const UInt32 CFE_AUTOCOLOR = 0x40000000;            // NOTE: this corresponds to 
    // CFM_COLOR, which controls it 
    // Masks and effects defined for CHARFORMAT2 -- an (*) indicates
    // that the data is stored by RichEdit 2.0/3.0, but not displayed
    const UInt32 CFE_SMALLCAPS = CFM_SMALLCAPS;
    const UInt32 CFE_ALLCAPS = CFM_ALLCAPS;
    const UInt32 CFE_HIDDEN = CFM_HIDDEN;
    const UInt32 CFE_OUTLINE = CFM_OUTLINE;
    const UInt32 CFE_SHADOW = CFM_SHADOW;
    const UInt32 CFE_EMBOSS = CFM_EMBOSS;
    const UInt32 CFE_IMPRINT = CFM_IMPRINT;
    const UInt32 CFE_DISABLED = CFM_DISABLED;
    const UInt32 CFE_REVISED = CFM_REVISED;

    // CFE_AUTOCOLOR and CFE_AUTOBACKCOLOR correspond to CFM_COLOR and
    // CFM_BACKCOLOR, respectively, which control them
    const UInt32 CFE_AUTOBACKCOLOR = CFM_BACKCOLOR;
    #endregion
    #region CFM_
    // CHARFORMAT masks 
    const UInt32 CFM_BOLD = 0x00000001;
    const UInt32 CFM_ITALIC = 0x00000002;
    const UInt32 CFM_UNDERLINE = 0x00000004;
    const UInt32 CFM_STRIKEOUT = 0x00000008;
    const UInt32 CFM_PROTECTED = 0x00000010;
    const UInt32 CFM_LINK = 0x00000020;         // Exchange hyperlink extension 
    const UInt32 CFM_SIZE = 0x80000000;
    const UInt32 CFM_COLOR = 0x40000000;
    const UInt32 CFM_FACE = 0x20000000;
    const UInt32 CFM_OFFSET = 0x10000000;
    const UInt32 CFM_CHARSET = 0x08000000;

    const UInt32 CFM_SMALLCAPS = 0x0040;            // (*)  
    const UInt32 CFM_ALLCAPS = 0x0080;          // Displayed by 3.0 
    const UInt32 CFM_HIDDEN = 0x0100;           // Hidden by 3.0 
    const UInt32 CFM_OUTLINE = 0x0200;          // (*)  
    const UInt32 CFM_SHADOW = 0x0400;           // (*)  
    const UInt32 CFM_EMBOSS = 0x0800;           // (*)  
    const UInt32 CFM_IMPRINT = 0x1000;          // (*)  
    const UInt32 CFM_DISABLED = 0x2000;
    const UInt32 CFM_REVISED = 0x4000;

    const UInt32 CFM_BACKCOLOR = 0x04000000;
    const UInt32 CFM_LCID = 0x02000000;
    const UInt32 CFM_UNDERLINETYPE = 0x00800000;        // Many displayed by 3.0 
    const UInt32 CFM_WEIGHT = 0x00400000;
    const UInt32 CFM_SPACING = 0x00200000;      // Displayed by 3.0 
    const UInt32 CFM_KERNING = 0x00100000;      // (*)  
    const UInt32 CFM_STYLE = 0x00080000;        // (*)  
    const UInt32 CFM_ANIMATION = 0x00040000;        // (*)  
    const UInt32 CFM_REVAUTHOR = 0x00008000;

    const UInt32 CFE_SUBSCRIPT = 0x00010000;        // Superscript and subscript are 
    const UInt32 CFE_SUPERSCRIPT = 0x00020000;      //  mutually exclusive           

    const UInt32 CFM_SUBSCRIPT = (CFE_SUBSCRIPT | CFE_SUPERSCRIPT);
    const UInt32 CFM_SUPERSCRIPT = CFM_SUBSCRIPT;

    // CHARFORMAT "ALL" masks
    const UInt32 CFM_EFFECTS = (CFM_BOLD | CFM_ITALIC | CFM_UNDERLINE | CFM_COLOR |
                         CFM_STRIKEOUT | CFE_PROTECTED | CFM_LINK);
    const UInt32 CFM_ALL = (CFM_EFFECTS | CFM_SIZE | CFM_FACE | CFM_OFFSET | CFM_CHARSET);

    const UInt32 CFM_EFFECTS2 = (CFM_EFFECTS | CFM_DISABLED | CFM_SMALLCAPS | CFM_ALLCAPS
                        | CFM_HIDDEN | CFM_OUTLINE | CFM_SHADOW | CFM_EMBOSS
                        | CFM_IMPRINT | CFM_DISABLED | CFM_REVISED
                        | CFM_SUBSCRIPT | CFM_SUPERSCRIPT | CFM_BACKCOLOR);

    const UInt32 CFM_ALL2 = (CFM_ALL | CFM_EFFECTS2 | CFM_BACKCOLOR | CFM_LCID
                        | CFM_UNDERLINETYPE | CFM_WEIGHT | CFM_REVAUTHOR
                        | CFM_SPACING | CFM_KERNING | CFM_STYLE | CFM_ANIMATION);
    #endregion
}

More you ask?

I use most of this via a small utility class that wraps this for all the styles and font changes. This way you can change font-size and not change font name, etc.

class RichTextStyle
{   
    private readonly Control _textEdit;
    private readonly CHARFORMAT2 _charFormat;

    public RichTextStyle(RichTextBox te)
    {
        _textEdit = te;
        _charFormat = new CHARFORMAT2();
        _charFormat.cbSize = Marshal.SizeOf(_charFormat);
        SendMessage(te.Handle, EM_GETCHARFORMAT, SCF_SELECTION, ref _charFormat);
    }

    private void SetEffect(UInt32 mask, UInt32 effect, bool valid)
    {
        CHARFORMAT2 fmt = new CHARFORMAT2();
        fmt.cbSize = Marshal.SizeOf(fmt);
        fmt.dwMask = mask;
        fmt.dwEffects = valid ? effect : 0;
        SendMessage(_textEdit.Handle, EM_SETCHARFORMAT, SCF_SELECTION, ref fmt);
    }

    private bool GetEffect(UInt32 mask, UInt32 effect)
    {
        return (0 != (_charFormat.dwMask & mask)) && (0 != (_charFormat.dwEffects & effect));
    }

    public bool Bold { get { return GetEffect(CFM_BOLD, CFE_BOLD); } set { SetEffect(CFM_BOLD, CFE_BOLD, value); } }
    public bool Italic { get { return GetEffect(CFM_ITALIC, CFE_ITALIC); } set { SetEffect(CFM_ITALIC, CFE_ITALIC, value); } }

    // ... etc ... etc ... you get the idea.

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