如何在C#使RichTextBox的打印格式与文本框内的原始格式一致

dfhs85 2009-08-30 08:59:29

如题：
打印RichTextBox的内容时，总会发现打印出来的字间距及行间距与RichTextBox内的字间距及行间距不符，请教各位大侠，如何让他们一致。

我是调用API进行打印的，代码如下：

using System;
using System.Windows.Forms;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Drawing.Printing;

namespace RichTextBoxPrintCtrl
{
public class RichTextBoxPrintCtrl : RichTextBox
{
//Convert the unit used by the .NET framework (1/100 inch)
//and the unit used by Win32 API calls (twips 1/1440 inch)

private const double anInch = 14.4;

[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
}

[StructLayout(LayoutKind.Sequential)]
private struct CHARRANGE
{
public int cpMin; //First character of range (0 for start of doc)
public int cpMax; //Last character of range (-1 for end of doc)
}

[StructLayout(LayoutKind.Sequential)]
private struct FORMATRANGE
{
public IntPtr hdc; //Actual DC to draw on
public IntPtr hdcTarget; //Target DC for determining text formatting
public RECT rc; //Region of the DC to draw to (in twips)
public RECT rcPage; //Region of the whole DC (page size) (in twips)
public CHARRANGE chrg; //Range of text to draw (see earlier declaration)
}

private const int WM_USER = 0x0400;
private const int EM_FORMATRANGE = WM_USER + 57;

[DllImport("USER32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

// Render the contents of the RichTextBox for printing
// Return the last character printed + 1 (printing start from this point for next page)
public int Print(int charFrom, int charTo, PrintPageEventArgs e)
{
//Calculate the area to render and print
RECT rectToPrint;
rectToPrint.Top = (int)(e.MarginBounds.Top * anInch);
rectToPrint.Bottom = (int)(e.MarginBounds.Bottom * anInch);
rectToPrint.Left = (int)(e.MarginBounds.Left * anInch);
rectToPrint.Right = (int)(e.MarginBounds.Right * anInch);

//Calculate the size of the page
RECT rectPage;
rectPage.Top = (int)(e.PageBounds.Top * anInch);
rectPage.Bottom = (int)(e.PageBounds.Bottom * anInch);
rectPage.Left = (int)(e.PageBounds.Left * anInch);
rectPage.Right = (int)(e.PageBounds.Right * anInch);

IntPtr hdc = e.Graphics.GetHdc();

FORMATRANGE fmtRange;
fmtRange.chrg.cpMax = charTo; //Indicate character from to character to
fmtRange.chrg.cpMin = charFrom;
fmtRange.hdc = hdc; //Use the same DC for measuring and rendering
fmtRange.hdcTarget = hdc; //Point at printer hDC
fmtRange.rc = rectToPrint; //Indicate the area on page to print
fmtRange.rcPage = rectPage; //Indicate size of page

IntPtr res = IntPtr.Zero;

IntPtr wparam = IntPtr.Zero;
wparam = new IntPtr(1);

//Get the pointer to the FORMATRANGE structure in memory
IntPtr lparam = IntPtr.Zero;
lparam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));
Marshal.StructureToPtr(fmtRange, lparam, false);

//Send the rendered data for printing
res = SendMessage(Handle, EM_FORMATRANGE, wparam, lparam);

//Free the block of memory allocated
Marshal.FreeCoTaskMem(lparam);

//Release the device context handle obtained by a previous call
e.Graphics.ReleaseHdc(hdc);

//Return last + 1 character printer
return res.ToInt32();
}
}
}

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