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Wait for me to hide

Posted on 1998-07-19
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Last Modified: 2013-11-20
I want to hide my application window then capture the screen. I tried the code below but the screen shot capture parts of my application window. How to make my application wait till its window is completely hidden?

 Here is the code that does not work:

IsHide = AfxGetMainWnd()->SetWindowPos(AfxGetMainWnd(),0,0,0,0,SWP_HIDEWINDOW);
      ASSERT(IsHide);
      AfxGetMainWnd()->UpdateWindow();   //Make sure it is hidden
       
            // Wait until everybody repaints themselves
        while (PeekMessage(&msg,NULL,0,0,PM_REMOVE) != 0)
          {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
          }
      }

      keybd_event(VK_SNAPSHOT,1,0,0); //full screen
.........

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Question by:khaledo
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3 Comments
 
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Accepted Solution

by:
atari earned 300 total points
ID: 1319453
I had a similar problem, I wanted to save the content of a mdi-window as .bmp after showing a CFileDialog for selecting a filename for my .bmp-file. After selecting a filename and clicking on OK the CFileDialog-Box is still displayed on the screen, so I cannot grab the content of my window. I solved this a little bit complicated with two timers, because the WM_TIMER-message  doesn't block any other messages, so all other messages are still processed. The problem for not updating the window-content is, that only after the end of your member-function the updating of your windows start, so the VK_UPDATE-message is much to early and will together processed while updating your windows.

So I solved it a little bit complicated, but it does work:
Start your screen-snapshot by calling AfxGetMainWnd()->OnBeginSnapshot();

Here are the protected declared functions in CMainFrame (my name for AfxGetMainWnd() in the following):

void CMainFrame::OnBeginSnapshot()
{
  ShowWindow(SW_HIDE);
  SetTimer(1,100,NULL);
  snapshot=TRUE;  // declared as protected in MainFrame.h
  endsnapshot=FALSE; // similar
}

void CMainFrame::OnSnapshot()
{
  keybd_event(VK_SNAPSHOT,1,0,0); //full screen
  KillTimer(1);
  SetTimer(1,100,NULL);
  snapshot=FALSE;
  endsnapshot=TRUE;
}

void CMainFrame::OnEndSnapshot()
{
  ShowWindow(SW_SHOWMAXIMIZED);
  KillTimer(1);
  snapshot=endsnapshot=FALSE;
}

void CMainFrame::OnTimer(UINT nIDEvent)
{
  if (snapshot)
      OnSnapshot();
  else
    if (endsnapshot)
        OnEndSnapshot();

  CMDIFrameWnd::OnTimer(nIDEvent);
}

The OnTimer()-call you can create with classwizard clicking on WM_TIMER-function for CMainFrame.

Maybe you can change the timer duration to get your best solution.

I hope this helps,
bye,
atari
0
 

Author Comment

by:khaledo
ID: 1319454
Thanks.

It worked, even when I set the timer to zero (because I thought it will be just like Wait() function if timer is not zero). I still do not understand why it worked. If updating starts after the end of the member function then we could simply put the function ShowWindow(SW_HIDE) in a separate member function and call it before the screen capturing. But such solution did not work while yours worked fine. If you can explain more I will be gratefull but for now, you solved my problem and I will accept your answer.
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LVL 1

Expert Comment

by:atari
ID: 1319455
I worked this problem out for several hours, tried everything like WaitForSingleObject() or SendMessage(WM_PAINT,0,0) for instantaneously redrawing the mainframe-window, but nothing seems to work. Somewhere I had read that the WM_TIMER-message doesn't block any other windows-message and if you read in help-file of VC++ you find 'The WM_TIMER message is a low-priority message.', what means that all higher priority messages like windows-redrawing and something else are first processed and the WM_TIMER is the last one that will be processed. Sorry, the statement, that refreshes begin after ending of member-function was my own mistake. I hope that you got a little more ideas about that !

Bye,
atari
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