打印RichTextBox

Question

我正在制作一个简单的WinForms应用程序，我想让用户从RichTextBox打印文本。

我跟着MSDN链路

但是如果我想使用某种PDF打印机呢？那么我必须说，当只打印一页时，它就能工作。每个下一页都是在相同的第一页上打印的，这意味着文本正在被重印。这是显而易见的，但是我能做什么来强制PDF打印机创建一个新的页面呢？

这是我的密码：

private PrintDocument docToPrint; 
private string stringToPrint;

public mainForm()
        {
            InitializeComponent();
            CenterToScreen();
            this.docToPrint = new PrintDocument();
            (...)
        }

private void tsBtnPrint_Click(object sender, EventArgs e)
        {
            PrintDialog myPrintDialog = new PrintDialog();
            myPrintDialog.AllowCurrentPage = true;
            myPrintDialog.AllowSelection = true;
            myPrintDialog.AllowSomePages = true;
            myPrintDialog.Document = docToPrint;
            if(myPrintDialog.ShowDialog()==DialogResult.OK)
            {
                StringReader reader = new StringReader(this.richTextBox.Text);
                stringToPrint = reader.ReadToEnd();
                this.docToPrint.PrintPage += new PrintPageEventHandler(this.docToPrintCustom);
                this.docToPrint.Print();
            }
        }

 private void docToPrintCustom(object sender, PrintPageEventArgs e)
        {
            Font PrintFont = this.richTextBox.Font;
            SolidBrush PrintBrush = new SolidBrush(Color.Black); 

            int LinesPerPage = 0;
            int charactersOnPage = 0;

            e.Graphics.MeasureString(stringToPrint, PrintFont, e.MarginBounds.Size, StringFormat.GenericTypographic,
                out charactersOnPage, out LinesPerPage);

            e.Graphics.DrawString(stringToPrint, PrintFont, PrintBrush, e.MarginBounds, StringFormat.GenericTypographic);

            stringToPrint = stringToPrint.Substring(charactersOnPage);

            MessageBox.Show(stringToPrint.Length.ToString());
            e.HasMorePages = (stringToPrint.Length > 0);

            PrintBrush.Dispose();
        }

我该怎么做才能以适当的方式打印下一页？

Answer 1

您可以通过向RuchTextBox发送EM_FORMATRANGE消息来打印它的内容。

此消息通常用于格式化输出设备(如打印机)的富编辑控件的内容。

要实现此解决方案，可以执行以下步骤：

• 首先，创建一个继承自RichTextBox的RichTextBox类，并实现一个FormatRange方法，该方法的任务是打印控件内容的每个页面。完整的代码如下所示。
• 然后创建一个Form并在其上放置一个RichTextBoxEx、PrintDocument，并处理PrintDocument的BeginPrint、PrintPage和EndPrint事件，并使用以下代码执行打印。

请注意

1. 使用这种方法，您可以打印控件的内容，并将所有格式应用于文本，这比以黑色打印一种字体和大小的所有文本要好。此外，您还可以将内容的字体和大小设置为一种字体、大小和颜色。
2. 创建RichtextBoxEx只是为了封装，而且是完全可选的，如果您想使用现有控件，只需使用我下面提供的FormatRange方法的内容，然后将控件的属性传递给它以执行打印。

支持打印的RichTextBoxEx：

这是我上面描述的完整的工作代码。代码是从Martinüller的msdn文章从.NET RichTextBox获取所见即所得打印结果文章中提取的。

public class RichTextBoxEx : RichTextBox
{
    [StructLayout(LayoutKind.Sequential)]
    private struct STRUCT_RECT
    {
        public Int32 left;
        public Int32 top;
        public Int32 right;
        public Int32 bottom;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct STRUCT_CHARRANGE
    {
        public Int32 cpMin;
        public Int32 cpMax;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct STRUCT_FORMATRANGE
    {
        public IntPtr hdc;
        public IntPtr hdcTarget;
        public STRUCT_RECT rc;
        public STRUCT_RECT rcPage;
        public STRUCT_CHARRANGE chrg;
    }

    [DllImport("user32.dll")]
    private static extern Int32 SendMessage(IntPtr hWnd, Int32 msg, Int32 wParam, IntPtr lParam);

    private const Int32 WM_USER = 0x400;
    private const Int32 EM_FORMATRANGE = WM_USER + 57;
    private const Int32 EM_GETCHARFORMAT = WM_USER + 58;
    private const Int32 EM_SETCHARFORMAT = WM_USER + 68;

    /// <summary>
    /// Calculate or render the contents of our RichTextBox for printing
    /// </summary>
    /// <param name="measureOnly">If true, only the calculation is performed, otherwise the text is rendered as well</param>
    /// <param name="e">The PrintPageEventArgs object from the PrintPage event</param>
    /// <param name="charFrom">Index of first character to be printed</param>
    /// <param name="charTo">Index of last character to be printed</param>
    /// <returns> (Index of last character that fitted on the page) + 1</returns>
    public int FormatRange(bool measureOnly, PrintPageEventArgs e, int charFrom, int charTo)
    {
        // Specify which characters to print
        STRUCT_CHARRANGE cr = default(STRUCT_CHARRANGE);
        cr.cpMin = charFrom;
        cr.cpMax = charTo;

        // Specify the area inside page margins
        STRUCT_RECT rc = default(STRUCT_RECT);
        rc.top = HundredthInchToTwips(e.MarginBounds.Top);
        rc.bottom = HundredthInchToTwips(e.MarginBounds.Bottom);
        rc.left = HundredthInchToTwips(e.MarginBounds.Left);
        rc.right = HundredthInchToTwips(e.MarginBounds.Right);

        // Specify the page area
        STRUCT_RECT rcPage = default(STRUCT_RECT);
        rcPage.top = HundredthInchToTwips(e.PageBounds.Top);
        rcPage.bottom = HundredthInchToTwips(e.PageBounds.Bottom);
        rcPage.left = HundredthInchToTwips(e.PageBounds.Left);
        rcPage.right = HundredthInchToTwips(e.PageBounds.Right);

        // Get device context of output device
        IntPtr hdc = default(IntPtr);
        hdc = e.Graphics.GetHdc();

        // Fill in the FORMATRANGE structure
        STRUCT_FORMATRANGE fr = default(STRUCT_FORMATRANGE);
        fr.chrg = cr;
        fr.hdc = hdc;
        fr.hdcTarget = hdc;
        fr.rc = rc;
        fr.rcPage = rcPage;

        // Non-Zero wParam means render, Zero means measure
        Int32 wParam = default(Int32);
        if (measureOnly)
        {
            wParam = 0;
        }
        else
        {
            wParam = 1;
        }

        // Allocate memory for the FORMATRANGE struct and
        // copy the contents of our struct to this memory
        IntPtr lParam = default(IntPtr);
        lParam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fr));
        Marshal.StructureToPtr(fr, lParam, false);

        // Send the actual Win32 message
        int res = 0;
        res = SendMessage(Handle, EM_FORMATRANGE, wParam, lParam);

        // Free allocated memory
        Marshal.FreeCoTaskMem(lParam);

        // and release the device context
        e.Graphics.ReleaseHdc(hdc);

        return res;
    }

    /// <summary>
    /// Convert between 1/100 inch (unit used by the .NET framework)
    /// and twips (1/1440 inch, used by Win32 API calls)
    /// </summary>
    /// <param name="n">Value in 1/100 inch</param>
    /// <returns>Value in twips</returns>
    private Int32 HundredthInchToTwips(int n)
    {
        return Convert.ToInt32(n * 14.4);
    }

    /// <summary>
    /// Free cached data from rich edit control after printing
    /// </summary>
    public void FormatRangeDone()
    {
        IntPtr lParam = new IntPtr(0);
        SendMessage(Handle, EM_FORMATRANGE, 0, lParam);
    }
}

用法示例：

private void printDocument1_BeginPrint(object sender, System.Drawing.Printing.PrintEventArgs e)
{
    // Start at the beginning of the text
    firstCharOnPage = 0;
}

private void printDocument1_EndPrint(object sender, System.Drawing.Printing.PrintEventArgs e)
{
    // Clean up cached information
    richTextBoxEx1.FormatRangeDone();
}

private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
{
    firstCharOnPage = richTextBoxEx1.FormatRange(false, e, firstCharOnPage, richTextBoxEx1.TextLength);
    // check if there are more pages to print
    if (firstCharOnPage < richTextBoxEx1.TextLength)
        e.HasMorePages = true;
    else
        e.HasMorePages = false;
}

private void printToolStripButton_Click(object sender, EventArgs e)
{
    //Print the contents here
    printDocument1.Print();
}