EmersonH.Com

Imports System
Imports System.Text
Imports System.Drawing.Printing
Imports System.Windows.Forms
Imports System.Runtime.InteropServices

Public Class RichTextBoxPrinter
'--- P/Invoke declarations
_
Private Structure CHARRANGE
Public cpMin As Integer
Public cpMax As Integer
End Structure
_
Private Structure RECT
Public Left As Integer
Public Top As Integer
Public Right As Integer
Public Bottom As Integer
End Structure
_
Private Structure FORMATRANGE
Public hdc As IntPtr
Public hdcTarget As IntPtr
Public rc As RECT
Public rcPage As RECT
Public chrg As CHARRANGE
End Structure
Private Const WM_USER As Integer = &H400
Private Const EM_FORMATRANGE As Integer = WM_USER + 57
Private Const Hundredth2Twips As Integer = 20 * 72 \ 100

Private Declare Auto Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal msg As Integer, ByVal wp As IntPtr, ByVal lp As IntPtr) As IntPtr

Public Shared Function Print(ByVal box As RichTextBox, ByRef charFrom As Integer, ByVal e As PrintPageEventArgs) As Boolean
'--- Prints text in , starting at .  Returns if more pages are needed
If box.Text.Length = 0 Then Return False
Dim fmtRange As FORMATRANGE
'--- Allocate device context for output device
Dim hdc As IntPtr = e.Graphics.GetHdc()
fmtRange.hdc = hdc
fmtRange.hdcTarget = hdc
'--- Set printable area, converted from 0.01" to twips
fmtRange.rc.Top = Convert.ToInt32(e.MarginBounds.Top * Hundredth2Twips)
fmtRange.rc.Bottom = Convert.ToInt32(e.MarginBounds.Bottom * Hundredth2Twips)
fmtRange.rc.Left = Convert.ToInt32(e.MarginBounds.Left * Hundredth2Twips)
fmtRange.rc.Right = Convert.ToInt32(e.MarginBounds.Right * Hundredth2Twips)
'--- Set page area, converted from 0.01" to twips
fmtRange.rcPage.Top = Convert.ToInt32(e.PageBounds.Top * Hundredth2Twips)
fmtRange.rcPage.Bottom = Convert.ToInt32(e.PageBounds.Bottom * Hundredth2Twips)
fmtRange.rcPage.Left = Convert.ToInt32(e.PageBounds.Left * Hundredth2Twips)
fmtRange.rcPage.Right = Convert.ToInt32(e.PageBounds.Right * Hundredth2Twips)
'--- Set character range to print
fmtRange.chrg.cpMin = charFrom
fmtRange.chrg.cpMax = box.TextLength
'--- Marshal to unmanaged memory
Dim hdlRange As IntPtr = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange))
Marshal.StructureToPtr(fmtRange, hdlRange, False)
'--- Send RichTextBox the EM_FORMATRANGE message to print the text
Dim res As IntPtr = SendMessage(box.Handle, EM_FORMATRANGE, CType(1, IntPtr), hdlRange)
Dim err As Integer = Marshal.GetLastWin32Error()
'--- Release resources
Marshal.FreeCoTaskMem(hdlRange)
e.Graphics.ReleaseHdc(hdc)
'--- Throw exception on error so we don't endlessly print an empty page
If (res = IntPtr.Zero) Then Throw New ApplicationException(String.Format("Printing failed, error code={0}", err))
'--- Update to next character to print, return if more pages needed
charFrom = res.ToInt32()
Return charFrom < box.TextLength
End Function
End Class