Re: Grabbing desktop image under a window

Hi Asm,

If you hide the window and then show it again you will disrupt the some
message like WM_MOVE. So your window will be very hard to move.

I did this using layered windows, it works pretty good, the only thing that
needs work is the flickering of the border. (NOTE: this will only work for
WinXP and above.)

BOOL CMagnifyDlg::OnInitDialog()
{
 CDialog::OnInitDialog();

   SetWindowLong(m_hWnd,GWL_EXSTYLE,GetWindowLong(m_hWnd, GWL_EXSTYLE) |
WS_EX_LAYERED);
   SetLayeredWindowAttributes(0,255,LWA_ALPHA);

   GetImage();

   return TRUE;
}

void CMagnifyDlg::GetImage()
{
    //make window completely transparent
   SetLayeredWindowAttributes(0,0,LWA_ALPHA);
   CRect Rect;
   GetClientRect(&Rect);
   ClientToScreen(&Rect);
   m_Bmp.DeleteObject();
   CDC *pDC = GetDesktopWindow()->GetDC();
   CDC MemDC;
   MemDC.CreateCompatibleDC(pDC);
   m_Bmp.CreateCompatibleBitmap(pDC,Rect.Width(),Rect.Height());
   int Saved = MemDC.SaveDC();
   MemDC.SelectObject(&m_Bmp);

   MemDC.BitBlt(0,0,Rect.Width(),Rect.Height(),pDC,Rect.left,Rect.top,SRCCOPY);

   MemDC.RestoreDC(Saved);
   GetDesktopWindow()->ReleaseDC(pDC);

   //bring the window back
   SetLayeredWindowAttributes(0,255,LWA_ALPHA);
   Invalidate();
}

void CMagnifyDlg::OnPaint()
{
   CPaintDC dc(this); // device context for painting

   CRect Rect;
   GetClientRect(&Rect);
   CDC MemDC;
   MemDC.CreateCompatibleDC(&dc);
   int Saved = MemDC.SaveDC();
   MemDC.SelectObject(&m_Bmp);
   dc.BitBlt(0,0,Rect.Width(),Rect.Height(),&MemDC,0,0,SRCCOPY);
   MemDC.RestoreDC(Saved);
}

AliR.

"MrAsm" <mrasm@usa.com> wrote in message
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