DrawBackground

HDC hdc = GetDC(m_hWnd)

m_hMemDC=CreateCompatibleDC(hdc) SelectObject m_hMemDC,m_hBKbitmap

m_hStretchedBitmap=CreateCompatibleBitmap(hdc,WndClintRect.right-WndClintRect.left,WndClintRect.bottom- WndClintRect.top)

m_hStretchedMem=CreateCompatibleDC(hdc)

SelectObject m_hStretchedMem,m_hStretchedBitmapReleaseDC m_hWnd, hdc

This is how you handle the sizing message WM_SIZE:

SelectObject m_hStretchedMem,m_hStretchedBitmapOld

DeleteObject m_hStretchedBitmap

HDC hdc = GetDC(m_hWnd) m_hStretchedBitmap=CreateCompatibleBitmap(hdc,WndClintRect.right- WndClintRect.left,WndClintRect.bottom- WndClintRect.top)

InvalidateRect m_hWnd,NULL,false

SelectObject m_hStretchedMem, m_hStretchedBitmap

ReleaseDC m_hWnd, hdc

before we draw the background we will pass the bitmap to the rich edit control so it would draw its background on the given bitmap. We will handle this in the background erasing of the main dialog

int SemiRichEditDlg::OnEraseBkgnd(WPARAM wParam, LPARAM lParam)

HDC hdc = (HDC)wParam

StretchBlt m_hStretchedMem, 0, 0, WndClintRect.right, WndClintRect.bottom, m_hMemDC, 0, 0, m_iBitmapWidth, m_iBitmapHight, SRCCOPY

 m_semiricheditctrl.DrawBackGround(hdc, m_hStretchedMem); BitBlt(hdc, 0, 0, WndClintRect.right - WndClintRect.left, WndClintRect.bottom - WndClintRect.top, m_hStretchedMem, 0, 0, SRCCOPY) return 1

How Does the Rich Edit draw its Background (Rich Edit to Bitmap)?

Now that we are almost done all we need to draw the background of the rich edit control to a bitmap and then copy it to the main window background(the main bitmap). So we need to create a bitmap the size of the rich edit background

' Creating A DC 

HDC hdcTransparent=CreateCompatibleDC(hdc)

'Creating a bitmap 

hTransparentBitmap=CreateCompatibleBitmap(hdc,m_RichEditRect.right-m_RichEditRect.left,m_RichEditRect.bottom-m_RichEditRect.top)

'Selecting the bitmap in to the created DC SelectObject hdcTransparent, hTransparentBitmap

'Fill the bitmap with white colour FloodFill hdcTransparent,0,0,RGB(255,255,255)

AlphaBlend hStretchedMem, m_RichEditRect.left + 1, m_RichEditRect.top + 1, m_RichEditRect.right - m_RichEditRect.left, m_RichEditRect.bottom - m_RichEditRect.top, hdcTransparent, 0, 0, m_RichEditRect.right - m_RichEditRect.left, m_RichEditRect.bottom - m_RichEditRect.top, blend

'Finding the size in twips 

nLogPixelsX =GetDeviceCaps(hdcTransparent, LOGPIXELSX)

nLogPixelsY =GetDeviceCaps(hdcTransparent, LOGPIXELSY)

rc.left=MulDiv(rc.left,1440, nLogPixelsX)

rc.top=MulDiv(rc.top,1440, nLogPixelsY)

rc.right=MulDiv(rc.right, 1440,nLogPixelsX)

rc.bottom=MulDiv(rc.bottom,1440, nLogPixelsY)

fr.hdc=hdcTransparent

fr.hdcTarget=hdcTransparent

fr.rc=rc

fr.rcPage=rc

fr.chrg.cpMin=SendMessage(m_hWnd, EM_CHARFROMPOS,(WPARAM) FALSE, <BR> (LPARAM) &point)

fr.chrg.cpMax=-1

'Requesting to draw on the DC 

lResult=SendMessage(m_hWnd, EM_FORMATRANGE,(WPARAM) TRUE, <BR> (LPARAM) &fr)

lResult=SendMessage(m_hWnd, EM_FORMATRANGE,(WPARAM) FALSE, <BR> (LPARAM) NULL)

BitBlt  hStretchedMem, m_RichEditRect.left + 1, m_RichEditRect.top + 1,<BR> m_RichEditRect.right - m_RichEditRect.left, <BR> m_RichEditRect.bottom - m_RichEditRect.top, hdcTransparent, 0, 0,SRCAND

EM_FORMATRANGE message

wParam

Specifies whether to render the text. If this parameter is not zero, the text is rendered. Otherwise, the text is just measured.

lParam

A FORMATRANGE structure containing information about the output device, or NULLto free information cached by the control.

Type FORMATRANGE

hdcTarget As Long

hdc As Long

rc As RECT

rcPage As RECT

chrg As CHARRANGE

End Type 

Type CHARRANGE 

cpMin As Long

cpMax As Long 

End Type

Private Const EM_DISPLAYBAND=&H451
Private Const EM_EXLINEFROMCHAR=&H454
Private Const EM_FORMATRANGE=&H457
Private Const EM_SETBKGNDCOLOR=&H467
Private Const EM_SETZOOM=&H625
 




EM_DISPLAYBAND message


Displays a portion of the contents of a rich edit control, as previously formatted for a device using the EM_FORMATRANGE message


Parameters

wParam

This parameter is not used; it must be zero.

lParam

A RECT structure specifying the display area of the device.