如何在不更改样式的情况下设置 RichTextBox.SelectionFont FontFamily？

Question

我的应用程序中的控件之一限制用户只能更改文本的字体样式（B、I、U）和颜色。为此，我创建了一个继承自 RichTextBox 的自定义控件。我能够拦截 CTRL-V，并将粘贴文本的字体设置为 SystemFonts.DefaultFont。我当前面临的问题是，如果粘贴的文本包含例如一半粗体一半常规样式 - 粗体就会丢失。

即“Foo Bar”将仅粘贴为“Foo Bar”。

我目前唯一的想法是逐个字符地浏览文本（非常慢），并执行以下操作：

public class MyRichTextBox : RichTextBox
{

private RichTextBox hiddenBuffer = new RichTextBox();

/// <summary>
/// This paste will strip the font size, family and alignment from the text being pasted.
/// </summary>
public void PasteUnformatted()
{
    this.hiddenBuffer.Clear();
    this.hiddenBuffer.Paste();

    for (int x = 0; x < this.hiddenBuffer.TextLength; x++)
    {
        // select the next character
        this.hiddenBuffer.Select(x, 1);

        // Set the font family and size to default
        this.hiddenBuffer.SelectionFont = new Font(SystemFonts.DefaultFont.FontFamily, SystemFonts.DefaultFont.Size, this.hiddenBuffer.SelectionFont.Style);
    }

    // Reset the alignment
    this.hiddenBuffer.SelectionAlignment = HorizontalAlignment.Left;

    base.SelectedRtf = this.hiddenBuffer.SelectedRtf;
    this.hiddenBuffer.Clear();
}

}

有人能想到更干净（更快）的解决方案吗？

Answer 1

MSDN 论坛上的“nobugz”为我回答了这个问题（我需要快速得到答案，所以在经历了近一天的风滚草之后，我不得不去其他地方寻找 - 不要评判我！）：

using System.Runtime.InteropServices;
...
        public static bool SetRtbFace(RichTextBox rtb, Font font, bool selectionOnly) {
            CHARFORMATW fmt = new CHARFORMATW();
            fmt.cbSize = Marshal.SizeOf(fmt);
            fmt.szFaceName = font.FontFamily.Name;
            fmt.dwMask = 0x20000000;  // CFM_FACE
            return IntPtr.Zero != SendMessage(rtb.Handle, 0x444, (IntPtr)(selectionOnly ? 1 : 4), fmt);
        }
        [StructLayout(LayoutKind.Sequential, Pack = 4)]
        private class CHARFORMATW {
            public int cbSize;
            public int dwMask;
            public int dwEffects;
            public int yHeight;
            public int yOffset;
            public int crTextColor;
            public byte bCharSet;
            public byte bPitchAndFamily;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 0x40)]
            public string szFaceName;
        }

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, CHARFORMATW lParam);

Answer 2

对于那些想要 Delphi 答案的人，摘录可以为您提供基本概念：

using RichEdit; //reqd. for the constants and types

var
  chformat : TCharFormat2;
  fontname : string;

begin
  FillChar(chformat,sizeof(chformat),0);
  chformat.cbSize := sizeof(chformat);
  //only modify the szFaceName field, height etc. left alone
  chformat.dwMask :=  CFM_FACE; 
  //get the fontname set by the user
  fontname := AdvFontSelector1.Text;
  strpcopy(chformat.szFaceName,fontname);
  RichEdit1.Perform(EM_SETCHARFORMAT, SCF_SELECTION, lparam(@chformat));
end;