Updateproblem when scrolling picture

[MagiMike]

I'm blitting som lines onto a static text or picture control.
It works fine until I shrink the window so that the scrollbars appear.
If the window is smaller than the picture control I get gray areas instead of white in the right and bottom areas of the picture control.
Is this a known bug or am I doing something wrong? I've been trying to call OnPaint wherever I can but it doesn't solve the problem.


Drawing code (OnPaint)
CWnd* wnd = GetDlgItem(IDC_GRAFVIEWER);
CBitmap bmp;
CBitmap *oBmp=&bmp;

CRect rect, temp;
wnd->GetWindowRect(rect);
wnd->GetClientRect(temp);
ScreenToClient(rect);

CDC *pDC, mDC;
pDC = GetDC();
mDC.CreateCompatibleDC(pDC);
bmp.CreateCompatibleBitmap(pDC, temp.right, temp.bottom);
oBmp = mDC.SelectObject(&bmp);

mDC.FillRect(temp, &CBrush(0xFFFFFF));

p->DrawPic(mDC); // Consists of drawing some lines

pDC->BitBlt(rect.left, rect.top, rect.right , rect.bottom, &mDC, 0, 0, SRCCOPY);

mDC.SelectObject(oBmp);
wnd->RedrawWindow();
ReleaseDC(pDC);
ReleaseDC(&mDC);

 

[MagiMike]

Figured it out myself. The problem is with the call to BitBlt when the whole window is not showed.
Apparently if I try to blit something bigger than the destination window (when made smaller) a portion does not get blitted.
I have to do some calculations with the rects for source and destination.