ArthurHub/ClipboardHelper.cs

## ClipboardHelper.cs
/// <summary>
/// Helper to encode and set HTML fragment to clipboard.<br/>
/// See http://theartofdev.com/2014/06/12/setting-htmltext-to-clipboard-revisited/.<br/>
/// <seealso cref="CreateDataObject"/>.
/// </summary>
/// <remarks>
/// The MIT License (MIT) Copyright (c) 2014 Arthur Teplitzki.
/// </remarks>
public static class ClipboardHelper
{
    #region Fields and Consts

    /// <summary>
    /// The string contains index references to other spots in the string, so we need placeholders so we can compute the offsets. <br/>
    /// The <![CDATA[<<<<<<<]]>_ strings are just placeholders. We'll back-patch them actual values afterwards. <br/>
    /// The string layout (<![CDATA[<<<]]>) also ensures that it can't appear in the body of the html because the <![CDATA[<]]> <br/>
    /// character must be escaped. <br/>
    /// </summary>
    private const string Header = @"Version:0.9
StartHTML:<<<<<<<<1
EndHTML:<<<<<<<<2
StartFragment:<<<<<<<<3
EndFragment:<<<<<<<<4
StartSelection:<<<<<<<<3
EndSelection:<<<<<<<<4";

    /// <summary>
    /// html comment to point the beginning of html fragment
    /// </summary>
    public const string StartFragment = "<!--StartFragment-->";

    /// <summary>
    /// html comment to point the end of html fragment
    /// </summary>
    public const string EndFragment = @"<!--EndFragment-->";

    /// <summary>
    /// Used to calculate characters byte count in UTF-8
    /// </summary>
    private static readonly char[] _byteCount = new char[1];

    #endregion


    /// <summary>
    /// Create <see cref="DataObject"/> with given html and plain-text ready to be used for clipboard or drag and drop.<br/>
    /// Handle missing <![CDATA[<html>]]> tags, specified start\end segments and Unicode characters.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Windows Clipboard works with UTF-8 Unicode encoding while .NET strings use with UTF-16 so for clipboard to correctly
    /// decode Unicode string added to it from .NET we needs to be re-encoded it using UTF-8 encoding.
    /// </para>
    /// <para>
    /// Builds the CF_HTML header correctly for all possible HTMLs<br/>
    /// If given html contains start/end fragments then it will use them in the header:
    /// <code><![CDATA[<html><body><!--StartFragment-->hello <b>world</b><!--EndFragment--></body></html>]]></code>
    /// If given html contains html/body tags then it will inject start/end fragments to exclude html/body tags:
    /// <code><![CDATA[<html><body>hello <b>world</b></body></html>]]></code>
    /// If given html doesn't contain html/body tags then it will inject the tags and start/end fragments properly:
    /// <code><![CDATA[hello <b>world</b>]]></code>
    /// In all cases creating a proper CF_HTML header:<br/>
    /// <code>
    /// <![CDATA[
    /// Version:1.0
    /// StartHTML:000000177
    /// EndHTML:000000329
    /// StartFragment:000000277
    /// EndFragment:000000295
    /// StartSelection:000000277
    /// EndSelection:000000277
    /// <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
    /// <html><body><!--StartFragment-->hello <b>world</b><!--EndFragment--></body></html>
    /// ]]>
    /// </code>
    /// See format specification here: http://msdn.microsoft.com/library/default.asp?url=/workshop/networking/clipboard/htmlclipboard.asp
    /// </para>
    /// </remarks>
    /// <param name="html">a html fragment</param>
    /// <param name="plainText">the plain text</param>
    public static DataObject CreateDataObject(string html, string plainText)
    {
        html = html ?? String.Empty;
        var htmlFragment = GetHtmlDataString(html);

        // re-encode the string so it will work correctly (fixed in CLR 4.0)
        if (Environment.Version.Major < 4 && html.Length != Encoding.UTF8.GetByteCount(html))
            htmlFragment = Encoding.Default.GetString(Encoding.UTF8.GetBytes(htmlFragment));

        var dataObject = new DataObject();
        dataObject.SetData(DataFormats.Html, htmlFragment);
        dataObject.SetData(DataFormats.Text, plainText);
        dataObject.SetData(DataFormats.UnicodeText, plainText);
        return dataObject;
    }

    /// <summary>
    /// Clears clipboard and sets the given HTML and plain text fragment to the clipboard, providing additional meta-information for HTML.<br/>
    /// See <see cref="CreateDataObject"/> for HTML fragment details.<br/>
    /// </summary>
    /// <example>
    /// ClipboardHelper.CopyToClipboard("Hello <b>World</b>", "Hello World");
    /// </example>
    /// <param name="html">a html fragment</param>
    /// <param name="plainText">the plain text</param>
    public static void CopyToClipboard(string html, string plainText)
    {
        var dataObject = CreateDataObject(html, plainText);
        Clipboard.SetDataObject(dataObject, true);
    }

    /// <summary>
    /// Generate HTML fragment data string with header that is required for the clipboard.
    /// </summary>
    /// <param name="html">the html to generate for</param>
    /// <returns>the resulted string</returns>
    private static string GetHtmlDataString(string html)
    {
        var sb = new StringBuilder();
        sb.AppendLine(Header);
        sb.AppendLine(@"<!DOCTYPE HTML PUBLIC ""-//W3C//DTD HTML 4.0 Transitional//EN"">");

        // if given html already provided the fragments we won't add them
        int fragmentStart, fragmentEnd;
        int fragmentStartIdx = html.IndexOf(StartFragment, StringComparison.OrdinalIgnoreCase);
        int fragmentEndIdx = html.LastIndexOf(EndFragment, StringComparison.OrdinalIgnoreCase);

        // if html tag is missing add it surrounding the given html (critical)
        int htmlOpenIdx = html.IndexOf("<html", StringComparison.OrdinalIgnoreCase);
        int htmlOpenEndIdx = htmlOpenIdx > -1 ? html.IndexOf('>', htmlOpenIdx) + 1 : -1;
        int htmlCloseIdx = html.LastIndexOf("</html", StringComparison.OrdinalIgnoreCase);

        if (fragmentStartIdx < 0 && fragmentEndIdx < 0)
        {
            int bodyOpenIdx = html.IndexOf("<body", StringComparison.OrdinalIgnoreCase);
            int bodyOpenEndIdx = bodyOpenIdx > -1 ? html.IndexOf('>', bodyOpenIdx) + 1 : -1;

            if (htmlOpenEndIdx < 0 && bodyOpenEndIdx < 0)
            {
                // the given html doesn't contain html or body tags so we need to add them and place start/end fragments around the given html only
                sb.Append("<html><body>");
                sb.Append(StartFragment);
                fragmentStart = GetByteCount(sb);
                sb.Append(html);
                fragmentEnd = GetByteCount(sb);
                sb.Append(EndFragment);
                sb.Append("</body></html>");
            }
            else
            {
                // insert start/end fragments in the proper place (related to html/body tags if exists) so the paste will work correctly
                int bodyCloseIdx = html.LastIndexOf("</body", StringComparison.OrdinalIgnoreCase);

                if (htmlOpenEndIdx < 0)
                    sb.Append("<html>");
                else
                    sb.Append(html, 0, htmlOpenEndIdx);

                if (bodyOpenEndIdx > -1)
                    sb.Append(html, htmlOpenEndIdx > -1 ? htmlOpenEndIdx : 0, bodyOpenEndIdx - (htmlOpenEndIdx > -1 ? htmlOpenEndIdx : 0));

                sb.Append(StartFragment);
                fragmentStart = GetByteCount(sb);

                var innerHtmlStart = bodyOpenEndIdx > -1 ? bodyOpenEndIdx : (htmlOpenEndIdx > -1 ? htmlOpenEndIdx : 0);
                var innerHtmlEnd = bodyCloseIdx > -1 ? bodyCloseIdx : (htmlCloseIdx > -1 ? htmlCloseIdx : html.Length);
                sb.Append(html, innerHtmlStart, innerHtmlEnd - innerHtmlStart);

                fragmentEnd = GetByteCount(sb);
                sb.Append(EndFragment);

                if (innerHtmlEnd < html.Length)
                    sb.Append(html, innerHtmlEnd, html.Length - innerHtmlEnd);

                if (htmlCloseIdx < 0)
                    sb.Append("</html>");
            }
        }
        else
        {
            // handle html with existing start\end fragments just need to calculate the correct bytes offset (surround with html tag if missing)
            if (htmlOpenEndIdx < 0)
                sb.Append("<html>");
            int start = GetByteCount(sb);
            sb.Append(html);
            fragmentStart = start + GetByteCount(sb, start, start + fragmentStartIdx) + StartFragment.Length;
            fragmentEnd = start + GetByteCount(sb, start, start + fragmentEndIdx);
            if (htmlCloseIdx < 0)
                sb.Append("</html>");
        }

        // Back-patch offsets (scan only the header part for performance)
        sb.Replace("<<<<<<<<1", Header.Length.ToString("D9"), 0, Header.Length);
        sb.Replace("<<<<<<<<2", GetByteCount(sb).ToString("D9"), 0, Header.Length);
        sb.Replace("<<<<<<<<3", fragmentStart.ToString("D9"), 0, Header.Length);
        sb.Replace("<<<<<<<<4", fragmentEnd.ToString("D9"), 0, Header.Length);

        return sb.ToString();
    }

    /// <summary>
    /// Calculates the number of bytes produced by encoding the string in the string builder in UTF-8 and not .NET default string encoding.
    /// </summary>
    /// <param name="sb">the string builder to count its string</param>
    /// <param name="start">optional: the start index to calculate from (default - start of string)</param>
    /// <param name="end">optional: the end index to calculate to (default - end of string)</param>
    /// <returns>the number of bytes required to encode the string in UTF-8</returns>
    private static int GetByteCount(StringBuilder sb, int start = 0, int end = -1)
    {
        int count = 0;
        end = end > -1 ? end : sb.Length;
        for (int i = start; i < end; i++)
        {
            _byteCount[0] = sb[i];
            count += Encoding.UTF8.GetByteCount(_byteCount);
        }
        return count;
    }
}
	/// <summary>
	/// Helper to encode and set HTML fragment to clipboard.<br/>
	/// See http://theartofdev.com/2014/06/12/setting-htmltext-to-clipboard-revisited/.<br/>
	/// <seealso cref="CreateDataObject"/>.
	/// </summary>
	/// <remarks>
	/// The MIT License (MIT) Copyright (c) 2014 Arthur Teplitzki.
	/// </remarks>
	public static class ClipboardHelper
	{
	#region Fields and Consts

	/// <summary>
	/// The string contains index references to other spots in the string, so we need placeholders so we can compute the offsets. <br/>
	/// The <![CDATA[<<<<<<<]]>_ strings are just placeholders. We'll back-patch them actual values afterwards. <br/>
	/// The string layout (<![CDATA[<<<]]>) also ensures that it can't appear in the body of the html because the <![CDATA[<]]> <br/>
	/// character must be escaped. <br/>
	/// </summary>
	private const string Header = @"Version:0.9
	StartHTML:<<<<<<<<1
	EndHTML:<<<<<<<<2
	StartFragment:<<<<<<<<3
	EndFragment:<<<<<<<<4
	StartSelection:<<<<<<<<3
	EndSelection:<<<<<<<<4";

	/// <summary>
	/// html comment to point the beginning of html fragment
	/// </summary>
	public const string StartFragment = "<!--StartFragment-->";

	/// <summary>
	/// html comment to point the end of html fragment
	/// </summary>
	public const string EndFragment = @"<!--EndFragment-->";

	/// <summary>
	/// Used to calculate characters byte count in UTF-8
	/// </summary>
	private static readonly char[] _byteCount = new char[1];

	#endregion


	/// <summary>
	/// Create <see cref="DataObject"/> with given html and plain-text ready to be used for clipboard or drag and drop.<br/>
	/// Handle missing <![CDATA[<html>]]> tags, specified start\end segments and Unicode characters.
	/// </summary>
	/// <remarks>
	/// <para>
	/// Windows Clipboard works with UTF-8 Unicode encoding while .NET strings use with UTF-16 so for clipboard to correctly
	/// decode Unicode string added to it from .NET we needs to be re-encoded it using UTF-8 encoding.
	/// </para>
	/// <para>
	/// Builds the CF_HTML header correctly for all possible HTMLs<br/>
	/// If given html contains start/end fragments then it will use them in the header:
	/// <code><![CDATA[<html><body><!--StartFragment-->hello <b>world</b><!--EndFragment--></body></html>]]></code>
	/// If given html contains html/body tags then it will inject start/end fragments to exclude html/body tags:
	/// <code><![CDATA[<html><body>hello <b>world</b></body></html>]]></code>
	/// If given html doesn't contain html/body tags then it will inject the tags and start/end fragments properly:
	/// <code><![CDATA[hello <b>world</b>]]></code>
	/// In all cases creating a proper CF_HTML header:<br/>
	/// <code>
	/// <![CDATA[
	/// Version:1.0
	/// StartHTML:000000177
	/// EndHTML:000000329
	/// StartFragment:000000277
	/// EndFragment:000000295
	/// StartSelection:000000277
	/// EndSelection:000000277
	/// <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
	/// <html><body><!--StartFragment-->hello <b>world</b><!--EndFragment--></body></html>
	/// ]]>
	/// </code>
	/// See format specification here: http://msdn.microsoft.com/library/default.asp?url=/workshop/networking/clipboard/htmlclipboard.asp
	/// </para>
	/// </remarks>
	/// <param name="html">a html fragment</param>
	/// <param name="plainText">the plain text</param>
	public static DataObject CreateDataObject(string html, string plainText)
	{
	html = html ?? String.Empty;
	var htmlFragment = GetHtmlDataString(html);

	// re-encode the string so it will work correctly (fixed in CLR 4.0)
	if (Environment.Version.Major < 4 && html.Length != Encoding.UTF8.GetByteCount(html))
	htmlFragment = Encoding.Default.GetString(Encoding.UTF8.GetBytes(htmlFragment));

	var dataObject = new DataObject();
	dataObject.SetData(DataFormats.Html, htmlFragment);
	dataObject.SetData(DataFormats.Text, plainText);
	dataObject.SetData(DataFormats.UnicodeText, plainText);
	return dataObject;
	}

	/// <summary>
	/// Clears clipboard and sets the given HTML and plain text fragment to the clipboard, providing additional meta-information for HTML.<br/>
	/// See <see cref="CreateDataObject"/> for HTML fragment details.<br/>
	/// </summary>
	/// <example>
	/// ClipboardHelper.CopyToClipboard("Hello <b>World</b>", "Hello World");
	/// </example>
	/// <param name="html">a html fragment</param>
	/// <param name="plainText">the plain text</param>
	public static void CopyToClipboard(string html, string plainText)
	{
	var dataObject = CreateDataObject(html, plainText);
	Clipboard.SetDataObject(dataObject, true);
	}

	/// <summary>
	/// Generate HTML fragment data string with header that is required for the clipboard.
	/// </summary>
	/// <param name="html">the html to generate for</param>
	/// <returns>the resulted string</returns>
	private static string GetHtmlDataString(string html)
	{
	var sb = new StringBuilder();
	sb.AppendLine(Header);
	sb.AppendLine(@"<!DOCTYPE HTML PUBLIC ""-//W3C//DTD HTML 4.0 Transitional//EN"">");

	// if given html already provided the fragments we won't add them
	int fragmentStart, fragmentEnd;
	int fragmentStartIdx = html.IndexOf(StartFragment, StringComparison.OrdinalIgnoreCase);
	int fragmentEndIdx = html.LastIndexOf(EndFragment, StringComparison.OrdinalIgnoreCase);

	// if html tag is missing add it surrounding the given html (critical)
	int htmlOpenIdx = html.IndexOf("<html", StringComparison.OrdinalIgnoreCase);
	int htmlOpenEndIdx = htmlOpenIdx > -1 ? html.IndexOf('>', htmlOpenIdx) + 1 : -1;
	int htmlCloseIdx = html.LastIndexOf("</html", StringComparison.OrdinalIgnoreCase);

	if (fragmentStartIdx < 0 && fragmentEndIdx < 0)
	{
	int bodyOpenIdx = html.IndexOf("<body", StringComparison.OrdinalIgnoreCase);
	int bodyOpenEndIdx = bodyOpenIdx > -1 ? html.IndexOf('>', bodyOpenIdx) + 1 : -1;

	if (htmlOpenEndIdx < 0 && bodyOpenEndIdx < 0)
	{
	// the given html doesn't contain html or body tags so we need to add them and place start/end fragments around the given html only
	sb.Append("<html><body>");
	sb.Append(StartFragment);
	fragmentStart = GetByteCount(sb);
	sb.Append(html);
	fragmentEnd = GetByteCount(sb);
	sb.Append(EndFragment);
	sb.Append("</body></html>");
	}
	else
	{
	// insert start/end fragments in the proper place (related to html/body tags if exists) so the paste will work correctly
	int bodyCloseIdx = html.LastIndexOf("</body", StringComparison.OrdinalIgnoreCase);

	if (htmlOpenEndIdx < 0)
	sb.Append("<html>");
	else
	sb.Append(html, 0, htmlOpenEndIdx);

	if (bodyOpenEndIdx > -1)
	sb.Append(html, htmlOpenEndIdx > -1 ? htmlOpenEndIdx : 0, bodyOpenEndIdx - (htmlOpenEndIdx > -1 ? htmlOpenEndIdx : 0));

	sb.Append(StartFragment);
	fragmentStart = GetByteCount(sb);

	var innerHtmlStart = bodyOpenEndIdx > -1 ? bodyOpenEndIdx : (htmlOpenEndIdx > -1 ? htmlOpenEndIdx : 0);
	var innerHtmlEnd = bodyCloseIdx > -1 ? bodyCloseIdx : (htmlCloseIdx > -1 ? htmlCloseIdx : html.Length);
	sb.Append(html, innerHtmlStart, innerHtmlEnd - innerHtmlStart);

	fragmentEnd = GetByteCount(sb);
	sb.Append(EndFragment);

	if (innerHtmlEnd < html.Length)
	sb.Append(html, innerHtmlEnd, html.Length - innerHtmlEnd);

	if (htmlCloseIdx < 0)
	sb.Append("</html>");
	}
	}
	else
	{
	// handle html with existing start\end fragments just need to calculate the correct bytes offset (surround with html tag if missing)
	if (htmlOpenEndIdx < 0)
	sb.Append("<html>");
	int start = GetByteCount(sb);
	sb.Append(html);
	fragmentStart = start + GetByteCount(sb, start, start + fragmentStartIdx) + StartFragment.Length;
	fragmentEnd = start + GetByteCount(sb, start, start + fragmentEndIdx);
	if (htmlCloseIdx < 0)
	sb.Append("</html>");
	}

	// Back-patch offsets (scan only the header part for performance)
	sb.Replace("<<<<<<<<1", Header.Length.ToString("D9"), 0, Header.Length);
	sb.Replace("<<<<<<<<2", GetByteCount(sb).ToString("D9"), 0, Header.Length);
	sb.Replace("<<<<<<<<3", fragmentStart.ToString("D9"), 0, Header.Length);
	sb.Replace("<<<<<<<<4", fragmentEnd.ToString("D9"), 0, Header.Length);

	return sb.ToString();
	}

	/// <summary>
	/// Calculates the number of bytes produced by encoding the string in the string builder in UTF-8 and not .NET default string encoding.
	/// </summary>
	/// <param name="sb">the string builder to count its string</param>
	/// <param name="start">optional: the start index to calculate from (default - start of string)</param>
	/// <param name="end">optional: the end index to calculate to (default - end of string)</param>
	/// <returns>the number of bytes required to encode the string in UTF-8</returns>
	private static int GetByteCount(StringBuilder sb, int start = 0, int end = -1)
	{
	int count = 0;
	end = end > -1 ? end : sb.Length;
	for (int i = start; i < end; i++)
	{
	_byteCount[0] = sb[i];
	count += Encoding.UTF8.GetByteCount(_byteCount);
	}
	return count;
	}
	}