getting hidden windows content

hi.

i am trying to get the contents of a visible (in the sense of WM_VISIBLE) but hidden (meaning blocked by other windows) window.

i have tried the following code, but it only produces a completely black image:

Code:

void PrintWindow(CWnd* window) //handle to window in question
{
	//memory DC
	CDC memDC;   
	
	//DC of window in question
	CDC *pDC = (*window).GetDC(); 
	
	//make the memory DC compatible to window DC
	memDC.CreateCompatibleDC(pDC); 


	//create a bitmap compatible to window DC, here just using 100x100
	CBitmap bitmap;
	bitmap.CreateCompatibleBitmap(pDC, 100, 100); 
		
	
	//select the bitmap into memory DC
	CBitmap *pOldBitmap = (CBitmap *)memDC.SelectObject(&bitmap); 


	//sendmessage to window to print itself into memory DC
	(*window).SendMessage(WM_PRINT, (WPARAM)memDC.GetSafeHdc(), PRF_CLIENT | PRF_ERASEBKGND | PRF_NONCLIENT ); 


	//create the desktop DC to display the result
	CDC desktop;
	desktop.CreateDC("DISPLAY",NULL,NULL,NULL);


	//bit to bit transfer of memory DC onto the desktop
	desktop.BitBlt(0,0,100,100,&memDC,0,0,SRCCOPY);

	//this now shows a black rectangle on the top left corner of my desktop

	//then comes some cleanup (release all the DC's etc...

}

if instead of

Code:

	(*window).SendMessage(WM_PRINT, (WPARAM)memDC.GetSafeHdc(), PRF_CLIENT | PRF_ERASEBKGND | PRF_NONCLIENT );

i use

Code:

 	memDC.BitBlt(0,0,100,100,pDC,0,0,SRCCOPY);

and then display memDC (again by bitblt) to desktop, then the correct image is shown (top left box of window), but
only if the window is visible.

which is why i used sendmessage with WM_PRINT.

please help if you can, as this is coming a major obstacle in my application.
i am using windows xp with service pack 2.

thanks to everyone reading this.

imran

Perhaps a MOD can move this to windows programming board, it is not standartd C++

USE CODE TAGS

I don't really understand, what you are trying to do. Are you trying to activate a window?

Window Contents Capturing using WM_PRINT Message