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
