// Sample class for Copying and Pasting HTML fragments to and from the clipboard.
//
// Mike Stall. https://blogs.msdn.com/jmstall
//
using System;
using System.Diagnostics;
using System.Windows.Forms;
using System.Text.RegularExpressions;
using System.Collections.Generic;
using System.Text;
using System.IO;
/// <summary>
/// Helper class to decode HTML from the clipboard.
/// See https://blogs.msdn.com/jmstall/archive/2007/01/21/html-clipboard.aspx for details.
/// </summary>
class HtmlFragment
{
#region Read and decode from clipboard
/// <summary>
/// Get a HTML fragment from the clipboard.
/// </summary>
/// <example>
/// string html = "<b>Hello!</b>";
/// HtmlFragment.CopyToClipboard(html);
/// HtmlFragment html2 = HtmlFragment.FromClipboard();
/// Debug.Assert(html2.Fragment == html);
/// </example>
static public HtmlFragment FromClipboard()
{
string rawClipboardText = Clipboard.GetText(TextDataFormat.Html);
HtmlFragment h = new HtmlFragment(rawClipboardText);
return h;
}
/// <summary>
/// Create an HTML fragment decoder around raw HTML text from the clipboard.
/// This text should have the header.
/// </summary>
/// <param name="rawClipboardText">raw html text, with header.</param>
public HtmlFragment(string rawClipboardText)
{
// This decodes CF_HTML, which is an entirely text format using UTF-8.
// Format of this header is described at:
// https://msdn.microsoft.com/library/default.asp?url=/workshop/networking/clipboard/htmlclipboard.asp
// Note the counters are byte counts in the original string, which may be Ansi. So byte counts
// may be the same as character counts (since sizeof(char) == 1).
// But System.String is unicode, and so byte couns are no longer the same as character counts,
// (since sizeof(wchar) == 2).
int startHMTL = 0;
int endHTML = 0;
int startFragment = 0;
int endFragment = 0;
Regex r;
Match m;
r = new Regex("([a-zA-Z]+):(.+?)[\r\n]",
RegexOptions.IgnoreCase | RegexOptions.Compiled);
for (m = r.Match(rawClipboardText); m.Success; m = m.NextMatch())
{
string key = m.Groups[1].Value.ToLower();
string val = m.Groups[2].Value;
switch(key)
{
// Version number of the clipboard. Starting version is 0.9.
case "version":
m_version = val;
break;
// Byte count from the beginning of the clipboard to the start of the context, or -1 if no context
case "starthtml":
if (startHMTL != 0) throw new FormatException("StartHtml is already declared");
startHMTL = int.Parse(val);
break;
// Byte count from the beginning of the clipboard to the end of the context, or -1 if no context.
case "endhtml":
if (startHMTL == 0) throw new FormatException("StartHTML must be declared before endHTML");
endHTML = int.Parse(val);
m_fullText = rawClipboardText.Substring(startHMTL, endHTML - startHMTL);
break;
// Byte count from the beginning of the clipboard to the start of the fragment.
case "startfragment":
if (startFragment != 0) throw new FormatException("StartFragment is already declared");
startFragment = int.Parse(val);
break;
// Byte count from the beginning of the clipboard to the end of the fragment.
case "endfragment":
if (startFragment == 0) throw new FormatException("StartFragment must be declared before EndFragment");
endFragment = int.Parse(val);
m_fragment = rawClipboardText.Substring(startFragment, endFragment - startFragment);
break;
// Optional Source URL, used for resolving relative links.
case "sourceurl":
m_source = new System.Uri(val);
break;
}
} // end for
if (m_fullText == null && m_fragment == null)
{
throw new FormatException("No data specified");
}
}
// Data. See properties for descriptions.
string m_version;
string m_fullText;
string m_fragment;
System.Uri m_source;
/// <summary>
/// Get the Version of the html. Usually something like "1.0".
/// </summary>
public string Version
{
get { return m_version; }
}
/// <summary>
/// Get the full text (context) of the HTML fragment. This includes tags that the HTML is enclosed in.
/// May be null if context is not specified.
/// </summary>
public string Context
{
get { return m_fullText; }
}
/// <summary>
/// Get just the fragment of HTML text.
/// </summary>
public string Fragment
{
get { return m_fragment; }
}
/// <summary>
/// Get the Source URL of the HTML. May be null if no SourceUrl is specified. This is useful for resolving relative urls.
/// </summary>
public System.Uri SourceUrl
{
get { return m_source; }
}
#endregion // Read and decode from clipboard
#region Write to Clipboard
// Helper to convert an integer into an 8 digit string.
// String must be 8 characters, because it will be used to replace an 8 character string within a larger string.
static string To8DigitString(int x)
{
return String.Format("{0,8}", x);
}
/// <summary>
/// Clears clipboard and copy a HTML fragment to the clipboard. This generates the header.
/// </summary>
/// <param name="htmlFragment">A html fragment.</param>
/// <example>
/// HtmlFragment.CopyToClipboard("<b>Hello!</b>");
/// </example>
public static void CopyToClipboard(string htmlFragment)
{
CopyToClipboard(htmlFragment, null, null);
}
/// <summary>
/// Clears clipboard and copy a HTML fragment to the clipboard, providing additional meta-information.
/// </summary>
/// <param name="htmlFragment">a html fragment</param>
/// <param name="title">optional title of the HTML document (can be null)</param>
/// <param name="sourceUrl">optional Source URL of the HTML document, for resolving relative links (can be null)</param>
public static void CopyToClipboard(string htmlFragment, string title, Uri sourceUrl)
{
if (title == null) title = "From Clipboard";
System.Text.StringBuilder sb = new System.Text.StringBuilder();
// Builds the CF_HTML header. See format specification here:
// https://msdn.microsoft.com/library/default.asp?url=/workshop/networking/clipboard/htmlclipboard.asp
// The string contains index references to other spots in the string, so we need placeholders so we can compute the offsets.
// The <<<<<<<_ strings are just placeholders. We'll backpatch them actual values afterwards.
// The string layout (<<<) also ensures that it can't appear in the body of the html because the <
// character must be escaped.
string header =
@"Format:HTML Format
Version:1.0
StartHTML:<<<<<<<1
EndHTML:<<<<<<<2
StartFragment:<<<<<<<3
EndFragment:<<<<<<<4
StartSelection:<<<<<<<3
EndSelection:<<<<<<<3
";
string pre =
@"<!DOCTYPE HTML PUBLIC ""-//W3C//DTD HTML 4.0 Transitional//EN"">
<HTML><HEAD><TITLE>" + title + @"</TITLE></HEAD><BODY><!--StartFragment-->";
string post = @"<!--EndFragment--></BODY></HTML>";
sb.Append(header);
if (sourceUrl != null)
{
sb.AppendFormat("SourceURL:{0}", sourceUrl);
}
int startHTML = sb.Length;
sb.Append(pre);
int fragmentStart = sb.Length;
sb.Append(htmlFragment);
int fragmentEnd = sb.Length;
sb.Append(post);
int endHTML = sb.Length;
// Backpatch offsets
sb.Replace("<<<<<<<1", To8DigitString(startHTML));
sb.Replace("<<<<<<<2", To8DigitString(endHTML));
sb.Replace("<<<<<<<3", To8DigitString(fragmentStart));
sb.Replace("<<<<<<<4", To8DigitString(fragmentEnd));
// Finally copy to clipboard.
string data = sb.ToString();
Clipboard.Clear();
Clipboard.SetText(data, TextDataFormat.Html);
}
#endregion // Write to Clipboard
} // end of class