扩展的 RichTextBox，用于保存和加载“HTML Lite”文件

Oscar Londono

4.97/5 (43投票s)

2005年11月5日

4分钟阅读

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此控件提供了一种直接保存和加载 HTML 文件的方法，避免使用 RTF 代码。

引言

在我开发一个聊天应用程序时，我发现 .NET 的 RichTextBox 控件只允许我使用 RTF 代码或纯文本文件保存和加载文件（天哪）。

我还想要一种将图像和 ActiveX 控件插入 RichTextBox 控件的方法，请参阅我的文章：通过 OLE 方法将图像插入 RichTextBox 控件。

好吧，我决定实现一个成功的解决方案，将“HTML lite”文本保存到 RichTextBox 控件中。它被称为“HTML lite”，因为我只处理其中一小部分 HTML 标签，并且有一些限制。但是，可以根据您的需求扩展该控件以包含其他功能和 HTML 标签处理器。

背景

我使用 Win32 API 来获取字符和段落格式结构。这应该比调用本地 RichTextBox 方法更有效，因为我相信每次调用 RichTextBox 方法都会进行一次系统 SendMessage 调用，并且我可以使用 PARAFORMAT 和 CHARFORMAT 结构一次性获取有关 RichTextBox 内容的更多信息。许多互联网网站和博客都采用了这种方法。

API

请参阅源代码了解更多详情。

[StructLayout( LayoutKind.Sequential )]
    public struct PARAFORMAT
{
    public int cbSize;
    public uint dwMask;
    ...
}

[ StructLayout( LayoutKind.Sequential )]
    public struct CHARFORMAT
{
    public int      cbSize; 
    public UInt32   dwMask; 
    public UInt32   dwEffects; 
    ...
}
//Constants
...

添加 HTML

要将 HTML 内容插入控件，我使用 AddHTML 方法。在此函数中，我查找起始 HTML 标签标记“<”并根据以下内容进行处理：

b    = bold
i    = italic
u    = underline
s    = strikeout
sup  = superscript
sub  = subscript
p    = paragraph (attributes: align="alignment")
font = font (attributes: face="facename" 
                      color="#rrggbb" size="NN")
li   = list item

这是该方法的源代码。请看一下我是如何使用 API 应用格式的，以及我如何忽略未处理的标签。我还尝试调整字体大小的值到最接近的值，因为它应该是 1 到 7 之间的数字。

// looking for start tags
int nStart = strHTML.IndexOf('<');
if (nStart >= 0)
{
  if (nStart > 0)
  {
    // tag is not the first character, so
    // we need to add text to control and continue
    // looking for tags at the begining of the text
    strData = strHTML.Substring(0, nStart);
    strHTML = strHTML.Substring(nStart);
  }
  else
  {
    // ok, get tag value
    int nEnd = strHTML.IndexOf('>', nStart);
    if (nEnd > nStart)
    {
      if ((nEnd - nStart) > 0)
      {
        string strTag = strHTML.Substring(nStart, 
                                   nEnd - nStart + 1);
        strTag = strTag.ToLower();

        if (strTag == "<b>")
        {
          cf.dwMask |= CFM_WEIGHT | CFM_BOLD;
          cf.dwEffects |= CFE_BOLD;
          cf.wWeight = FW_BOLD;
        }
        else if (strTag == "<i>")
        {
          cf.dwMask |= CFM_ITALIC;
          cf.dwEffects |= CFE_ITALIC;
        }
        else if (strTag == "<u>")
        {
          cf.dwMask |= CFM_UNDERLINE | CFM_UNDERLINETYPE;
          cf.dwEffects |= CFE_UNDERLINE;
          cf.bUnderlineType = CFU_UNDERLINE;
        }
        else if (strTag == "<s>")
        {
          cf.dwMask |= CFM_STRIKEOUT;
          cf.dwEffects |= CFE_STRIKEOUT;
        }
        else if (strTag == "<sup>")
        {
          cf.dwMask |= CFM_SUPERSCRIPT;
          cf.dwEffects |= CFE_SUPERSCRIPT;
        }
        else if (strTag == "<sub>")
        {
          cf.dwMask |= CFM_SUBSCRIPT;
          cf.dwEffects |= CFE_SUBSCRIPT;
        }
        else if ((strTag.Length > 2) && 
                (strTag.Substring(0, 2) == "<p"))
        {
          if (strTag.IndexOf("align=\"left\"") > 0)
          {
            pf.dwMask |= PFM_ALIGNMENT;
            pf.wAlignment = (short)PFA_LEFT;
          }
          else if (strTag.IndexOf("align=\"right\"") > 0)
          {
            pf.dwMask |= PFM_ALIGNMENT;
            pf.wAlignment = (short)PFA_RIGHT;
          }
          else if (strTag.IndexOf("align=\"center\"") > 0)
          {
            pf.dwMask |= PFM_ALIGNMENT;
            pf.wAlignment = (short)PFA_CENTER;
          }
        }
        else if ((strTag.Length > 5) && 
                (strTag.Substring(0, 5) == "<font")
        {
          string strFont = new string(cf.szFaceName);
          strFont = strFont.Trim(chtrim);
          int crFont = cf.crTextColor;
          int yHeight = cf.yHeight;

          int nFace = strTag.IndexOf("face=");
          if (nFace > 0)
          {
            int nFaceEnd = strTag.IndexOf("\""", nFace + 6);
            if (nFaceEnd > nFace)
                strFont = 
                    strTag.Substring(nFace + 6, nFaceEnd - nFace - 6);
          }

          int nSize = strTag.IndexOf("size=");
          if (nSize > 0)
          {
            int nSizeEnd = strTag.IndexOf("\""", nSize + 6);
            if (nSizeEnd > nSize)
            {
              yHeight = int.Parse(strTag.Substring(nSize + 6, 
                                             nSizeEnd - nSize - 6));
              yHeight *= (20 * 5);
            }
          }

          int nColor = strTag.IndexOf("color=");
          if (nColor > 0)
          {
            int nColorEnd = strTag.IndexOf("\""", nColor + 7);
            if (nColorEnd > nColor)
            {
              if (strTag.Substring(nColor + 7, 1) == "#")
              {
                string strCr = strTag.Substring(nColor + 8, 
                                      nColorEnd - nColor - 8);
                int nCr = Convert.ToInt32(strCr, 16);

                Color color = Color.FromArgb(nCr);

                crFont = GetCOLORREF(color);
              }
              else
              {
                crFont = int.Parse(strTag.Substring(nColor + 7, 
                                         nColorEnd - nColor - 7));
              }
            }
          }

          cf.szFaceName = new char[LF_FACESIZE];
          strFont.CopyTo(0, cf.szFaceName, 0, 
                     Math.Min(LF_FACESIZE - 1, strFont.Length));
          //cf.szFaceName = strFont.ToCharArray(0, 
                         Math.Min(strFont.Length, LF_FACESIZE));
          cf.crTextColor = crFont;
          cf.yHeight = yHeight;

          cf.dwMask |= CFM_COLOR | CFM_SIZE | CFM_FACE;
          cf.dwEffects &= ~CFE_AUTOCOLOR;
        }
        else if (strTag == "<li>")
        {
          if (pf.wNumbering != PFN_BULLET)
          {
            pf.dwMask |= PFM_NUMBERING;
            pf.wNumbering = (short)PFN_BULLET;
          }
        }
        else if (strTag == "</b>")
        {
          cf.dwEffects &= ~CFE_BOLD;
          cf.wWeight = FW_NORMAL;
        }
        else if (strTag == "</i>")
        {
          cf.dwEffects &= ~CFE_ITALIC;
        }
        else if (strTag == "</u>")
        {
          cf.dwEffects &= ~CFE_UNDERLINE;
        }
        else if (strTag == "</s>")
        {
          cf.dwEffects &= ~CFM_STRIKEOUT;
        }
        else if (strTag == "</sup>")
        {
          cf.dwEffects &= ~CFE_SUPERSCRIPT;
        }
        else if (strTag == "</sub>")
        {
          cf.dwEffects &= ~CFE_SUBSCRIPT;
        }
        else if (strTag == "</font>")
        {
        }
        else if (strTag == "</p>")
        {
        }
        else if (strTag == "")
        {
        }

        //-------------------------------
        // now, remove tag from HTML
        int nStart2 = strHTML.IndexOf("<", nEnd + 1);
        if (nStart2 > 0)
        {
          // extract partial data
          strData = strHTML.Substring(nEnd + 1, nStart2 - nEnd - 1);
          strHTML = strHTML.Substring(nStart2);
        }
        else
        {
          // get remain text and finish
          if ((nEnd + 1) < strHTML.Length)
            strData = strHTML.Substring(nEnd + 1);
          else
            strData = "";

          strHTML = "";
        }
        //-------------------------------s


        //-------------------------------
        // have we any continuos tag ?
        if (strData.Length > 0)
        {
          // yes, ok, goto to reinit
          if (strData[0] == '<')
            goto reinit;
        }
        //-------------------------------
      }
      else
      {
        // we have not found any valid tag
        strHTML = "";
      }
    }
    else
    {
      // we have not found any valid tag
      strHTML = "";
    }
  }
}
else
{
  // we have not found any tag
  strHTML = "";
}

为了通过 PARAFORMAT 和 CHARFORMAT 应用格式，我使用属性（一个从互联网上学到的好技巧）。请参阅源代码了解更多详情。

public PARAFORMAT ParaFormat
{
  get
  {
    PARAFORMAT pf = new PARAFORMAT();
    pf.cbSize = Marshal.SizeOf( pf );
      
    // Get the alignment.
    SendMessage( new HandleRef( this, Handle ),
      EM_GETPARAFORMAT,
      SCF_SELECTION, ref pf );
      
    return pf;
  }
  
  set
  {
    PARAFORMAT pf = value;
    pf.cbSize = Marshal.SizeOf( pf );
      
    // Set the alignment.
    SendMessage( new HandleRef( this, Handle ),
      EM_SETPARAFORMAT,
      SCF_SELECTION, ref pf );
  }
}

public PARAFORMAT DefaultParaFormat
{  
   ...
}

public CHARFORMAT CharFormat
{
   ...
}

public CHARFORMAT DefaultCharFormat
{
   ...
}

下面是如何使用其新属性将文本格式信息写入控件。变量 strData 包含应用格式之前的纯文本。

if (strData.Length > 0)
{
  //-------------------------------
  // replace entities
  strData = strData.Replace("&", "&");
  strData = strData.Replace("&lt;", "<");
  strData = strData.Replace("&gt;", ">");
  strData = strData.Replace("&apos;", "'");
  strData = strData.Replace("&quot;", "\""");
  //-------------------------------

  string strAux = strData; // use another copy

  while (strAux.Length > 0)
  {
    //-----------------------
    int nLen = strAux.Length;
    //-----------------------

    //-------------------------------
    // now, add text to control
    int nStartCache = this.SelectionStart;
    string strt = strAux.Substring(0, nLen);

    this.SelectedText = strt;
    strAux = strAux.Remove(0, nLen);

    this.SelectionStart = nStartCache;
    this.SelectionLength = strt.Length;
    //-------------------------------

    //-------------------------------
    // apply format
    this.ParaFormat = pf;
    this.CharFormat = cf;
    //-------------------------------


    // reposition to final
    this.SelectionStart = this.TextLength+1;
    this.SelectionLength = 0;
  }

  // reposition to final
  this.SelectionStart = this.TextLength+1;
  this.SelectionLength = 0;

  //-------------------------------
  // new paragraph requires to reset alignment
  if ((strData.IndexOf("\r\n", 0) >= 0) || 
                   (strData.IndexOf("\n", 0) >= 0))
  {
    pf.dwMask = PFM_ALIGNMENT|PFM_NUMBERING;
    pf.wAlignment = (short)PFA_LEFT;
    pf.wNumbering = 0;
  }
  //-------------------------------

从控件获取 HTML 内容

要从控件获取 HTML 内容，我使用以下方法：逐个字符地获取（*如果有人知道替代方法，请告诉我*）。

我逐个字符地对控件中的字符进行格式分析，并提取有关其样式的信息。如果字符格式或段落格式在任何时候发生更改，我会在原始文本中添加一个 HTML 标签。

这是通过使用内部结构 cMyREFormat 来实现的，该结构存储相关信息，例如位置和应该在该位置的标签。

private enum uMyREType
{
  U_MYRE_TYPE_TAG,
  U_MYRE_TYPE_EMO,
  U_MYRE_TYPE_ENTITY,
}

private struct cMyREFormat
{
  public uMyREType nType;
  public int nLen;
  public int nPos;
  public string strValue;
}

步骤 1

查找实体（&、<、>、"、'）并存储它们的位置。

char[] ch = {'&', '<', '>', '""', '\''};
string[] strreplace = {"&", "&lt;", "&gt;", 
                              "&quot;", "&apos;"};

for (i = 0; i < ch.Length; i++)
{
    char[] ch2 = {ch[i]};

    int n = this.Find(ch2, 0);
    while (n != -1)
    {
        mfr = new cMyREFormat();

        mfr.nPos = n;
        mfr.nLen = 1;
        mfr.nType = uMyREType.U_MYRE_TYPE_ENTITY;
        mfr.strValue = strreplace[i];

        colFormat.Add(mfr);

        n = this.Find(ch2, n+1);
    }
}

第二步

查找字体更改。

//-------------------------
// get format for this character
cf = this.CharFormat;
pf = this.ParaFormat;

string strfname = new string(cf.szFaceName);
strfname = strfname.Trim(chtrim);
//-------------------------


//-------------------------
// new font format ?
if ((strFont != strfname) || (crFont != cf.crTextColor) || 
                                    (yHeight != cf.yHeight))
{
    if (strFont != "")
    {
        // close previous <font> tag

        mfr = new cMyREFormat();

        mfr.nPos = i;
        mfr.nLen = 0;
        mfr.nType = uMyREType.U_MYRE_TYPE_TAG;
        mfr.strValue = "</font>";

        colFormat.Add(mfr);
    }

    //-------------------------
    // save this for cache
    strFont = strfname;
    crFont = cf.crTextColor;
    yHeight = cf.yHeight;
    //-------------------------

    //-------------------------
    // font size should be translate to 
    // html size (Approximately)
    int fsize = yHeight / (20 * 5);
    //-------------------------

    //-------------------------
    // color object from COLORREF
    color = GetColor(crFont);
    //-------------------------

    //-------------------------
    // add <font> tag
    mfr = new cMyREFormat();

    string strcolor = string.Concat("#", 
                 (color.ToArgb() & 0x00FFFFFF).ToString("X6"));

    mfr.nPos = i;
    mfr.nLen = 0;
    mfr.nType = uMyREType.U_MYRE_TYPE_TAG;
    mfr.strValue = "<font face=\"" + strFont + "\" color=\"" + 
                        strcolor + "\" size=\"" + fsize + "\">";;

    colFormat.Add(mfr);
    //-------------------------

步骤 3

查找段落格式更改，并在我们进入新段落时关闭之前的标签。这是通过使用状态来实现的。

none：未应用格式；
new：应用新的格式样式（、、...等）；
continue：格式与前一个相同（无更改）；
reset：关闭并重新开始（、、...等）。

//-------------------------
// are we in another line ?
if ((strChar == "\r") || (strChar == "\n"))
{
    // yes?
    // then, we need to reset paragraph format
    // and character format
    if (bParaFormat)
    {
        bnumbering = ctformatStates.nctNone;
        baleft = ctformatStates.nctNone;
        baright = ctformatStates.nctNone;
        bacenter = ctformatStates.nctNone;
    }

    // close previous tags

    // is italic? => close it
    if (bitalic != ctformatStates.nctNone)
    {
        mfr = new cMyREFormat();

        mfr.nPos = i;
        mfr.nLen = 0;
        mfr.nType = uMyREType.U_MYRE_TYPE_TAG;
        mfr.strValue = "</i>";

        colFormat.Add(mfr);

        bitalic = ctformatStates.nctNone;
    }

    // is bold? => close it
    if (bold != ctformatStates.nctNone)
    {
        ...
    }

    ...
}

// now, process the paragraph format,
// managing states: none, new, 
// continue {with previous}, reset
if (bParaFormat)
{
    // align to center?
    if (pf.wAlignment == PFA_CENTER)
    {
        if (bacenter == ctformatStates.nctNone)
            bacenter = ctformatStates.nctNew;
        else
            bacenter = ctformatStates.nctContinue;
    }
    else
    {
        if (bacenter != ctformatStates.nctNone)
            bacenter = ctformatStates.nctReset;
    }

    if (bacenter == ctformatStates.nctNew)
    {
        mfr = new cMyREFormat();

        mfr.nPos = i;
        mfr.nLen = 0;
        mfr.nType = uMyREType.U_MYRE_TYPE_TAG;
        mfr.strValue = "<p align='\"center\"'>";

        colFormat.Add(mfr);
    }
    else if (bacenter == ctformatStates.nctReset)
        bacenter = ctformatStates.nctNone;
    //---------------------

    //---------------------
    // align to left ?
    if (pf.wAlignment == PFA_LEFT)
    {
        ...
    }
    //---------------------

    //---------------------
    // align to right ?
    if (pf.wAlignment == PFA_RIGHT)
    {
        ...
    }
    //---------------------

    //---------------------
    // bullet ?
    if (pf.wNumbering == PFN_BULLET)
    {
        ...
    }
    //---------------------
}

步骤 4

查找样式更改：粗体、斜体、下划线、删除线（使用相同的方法，通过状态）。

//---------------------
// bold ?
if ((cf.dwEffects & CFE_BOLD) == CFE_BOLD)
{
    if (bold == ctformatStates.nctNone)
        bold = ctformatStates.nctNew;
    else
        bold = ctformatStates.nctContinue;
}
else
{
    if (bold != ctformatStates.nctNone)
        bold = ctformatStates.nctReset;
}

if (bold == ctformatStates.nctNew)
{
    mfr = new cMyREFormat();

    mfr.nPos = i;
    mfr.nLen = 0;
    mfr.nType = uMyREType.U_MYRE_TYPE_TAG;
    mfr.strValue = "<b>";

    colFormat.Add(mfr);
}
else if (bold == ctformatStates.nctReset)
{
    mfr = new cMyREFormat();

    mfr.nPos = i;
    mfr.nLen = 0;
    mfr.nType = uMyREType.U_MYRE_TYPE_TAG;
    mfr.strValue = "</b>";

    colFormat.Add(mfr);

    bold = ctformatStates.nctNone;
}
//---------------------

//---------------------
// Italic
if ((cf.dwEffects & CFE_ITALIC) == CFE_ITALIC)
{
    ...
}
//---------------------

...

步骤 5

对格式数组进行排序，并通过逐个添加字符和标签来应用样式，直到完成 HTML 文本。

//--------------------------
// now, reorder the formatting array
k = colFormat.Count;
for (i = 0; i < k - 1; i++)
{
    for (int j = i + 1; j < k; j++)
    {
        mfr = (cMyREFormat)colFormat[i];
        cMyREFormat mfr2 = (cMyREFormat)colFormat[j];

        if (mfr2.nPos < mfr.nPos)
        {
            colFormat.RemoveAt(j);
            colFormat.Insert(i, mfr2);
            j--;
        }
        else if ((mfr2.nPos == mfr.nPos) && 
                              (mfr2.nLen < mfr.nLen))
        {
            colFormat.RemoveAt(j);
            colFormat.Insert(i, mfr2);
            j--;
        }
    }
}
//--------------------------


//--------------------------
// apply format by replacing and inserting HTML tags
// stored in the Format Array
int nAcum = 0;
for (i = 0; i < k; i++)
{
    mfr = (cMyREFormat)colFormat[i];

    strHTML += 
       strT.Substring(nAcum, mfr.nPos - nAcum) + mfr.strValue;
    nAcum = mfr.nPos + mfr.nLen;
}

if (nAcum < strT.Length)
    strHTML += strT.Substring(nAcum);
//--------------------------

关注点

为了避免在应用字符和段落格式时进行不断的屏幕更新，我使用了 **Pete Vidler** 在文章 Extending RichTextBox 中提供的 **更快的更新** 方法。

这是通过向控件发送两个消息来实现的：EM_SETEVENTMASK 以防止控件引发任何事件，以及 WM_SETREDRAW 以防止控件重绘自身。

public void BeginUpdate()
{
    // Deal with nested calls.
    ++updating;
    
    if ( updating > 1 )
        return;
    
    // Prevent the control from raising any events.
    oldEventMask = SendMessage( new HandleRef( this, Handle ),
        EM_SETEVENTMASK, 0, 0 );
    
    // Prevent the control from redrawing itself.
    SendMessage( new HandleRef( this, Handle ),
        WM_SETREDRAW, 0, 0 );
}

/// <SUMMARY>
/// Resumes drawing and event handling.
/// </SUMMARY>
/// <REMARKS>
/// This method should be called every time a call is made
/// made to BeginUpdate. It resets the event mask to it's
/// original value and enables redrawing of the control.
/// </REMARKS>
public void EndUpdate()
{
    // Deal with nested calls.
    --updating;
    
    if ( updating > 0 )
        return;
    
    // Allow the control to redraw itself.
    SendMessage( new HandleRef( this, Handle ),
        WM_SETREDRAW, 1, 0 );

    // Allow the control to raise event messages.
    SendMessage( new HandleRef( this, Handle ),
        EM_SETEVENTMASK, 0, oldEventMask );
}

/// <SUMMARY>
/// Returns true when the control is performing some 
/// internal updates, specially when is reading or writing
/// HTML text
/// </SUMMARY>
public bool InternalUpdating
{
    get 
    {
        return (updating != 0);
    }
}

使用代码

要使用该代码，只需添加对 HmlRichTextBox 的引用，并调用 AddHTML 和 GetHTML 方法。

我使用一个带有格式按钮的工具栏。为了更新按钮状态，我处理 OnSelectionChanged 事件。请记住，在从/到 HTML 文本进行转换时，必须使用 InternalUpdating 属性来提高性能。

private void richTextBox1_SelectionChanged(object sender, 
                                         System.EventArgs e)
{
    if (!richTextBox1.InternalUpdating)
        UpdateToolbar(); //Update the toolbar buttons
}

/// <SUMMARY>
///     Update the toolbar button statuses
/// </SUMMARY>
public void UpdateToolbar()
{
    //This is done incase 2 different 
    //fonts are selected at the same time
    //If that is the case there is no 
    //selection font so I use the default
    //font instead.
    Font fnt;
    
    if (richTextBox1.SelectionFont != null)
        fnt = richTextBox1.SelectionFont;
    else
        fnt = richTextBox1.Font;

    //Do all the toolbar button checks
    tbbBold.Pushed      = fnt.Bold; //bold button
    tbbItalic.Pushed    = fnt.Italic; //italic button
    tbbUnderline.Pushed = fnt.Underline; //underline button
    tbbStrikeout.Pushed = fnt.Strikeout; //strikeout button
    tbbLeft.Pushed      = (richTextBox1.SelectionAlignment == 
                            HorizontalAlignment.Left); //justify left
    tbbCenter.Pushed    = (richTextBox1.SelectionAlignment == 
                            HorizontalAlignment.Center); //justify center
    tbbRight.Pushed     = (richTextBox1.SelectionAlignment == 
                            HorizontalAlignment.Right); //justify right
}

参考文献和致谢

Pete Vidler 的 Extending RichTextBox。
Richard Parsons 的 RichTextBoxExtended。

历史

2005年11月5日：版本 1.0
2005年12月5日：版本 1.1
- 添加了上标和下标样式。

注意

请提供您的评论、更正或要求致谢。您的反馈非常受欢迎！.

扩展的 RichTextBox， 用于保存和加载“HTML Lite”文件

引言

背景

API