Scrollbars in CMDIFrameWnd

Wendelin Reich -- wreich@gwdg.de
Thursday, May 16, 1996

******* G'day folks ********

Environment: VC++ 4.1 / Win 95

Task: In order to let the user use the scrollbars when a MDI-Childf gets
out of the client-area of the MDIFrame, I want the latter to support
Scrollbars.

My (wrong) solution: In my CMDIFrameWnd-derived class, I set the
Scrollbar-Styles as follows:

BOOL CMyownMDIFrameWnd::PreCreateWindow(CREATESTRUCT& cs)
{
    BOOL bRet = CMDIFrameWnd::PreCreateWindow(cs);

    cs.dwExStyle |= WS_VSCROLL | WS_HSCROLL;

    return bRet;
}

Problem: With this solution (and also when I set the style before
calling the parent::PreCreateWindow() !) I get (during the start-up
of the app) an *ASSERTION-failure* deep down in MFC, in (as the 
debugger says) file winocc.cpp:

CWnd* CWnd::GetDlgItem(something) {

   ASSERT(::IsWindow(m_hWnd));   // <-- here

   ...
}

What did I do wrong? How do I get Scrollbars (like in every other
Windows-App, like Word and Excel f.ex.)?

BTW, David Elliott wrote:

> Try changing the style before calling PreCreateWindow().

As said, I tried this before, but it makes no difference...

-- 
cu/ru...

   Wendelin Reich                                       wreich@gwdg.de
   Dept. of Economic Geography              Tel (Job):  +49-551-398088
   Geographisches Institut der              Tel (priv.): +49-551-35906
   Universitaet Goettingen
   D-37077 Goettingen, Germany

---

Frederic Steppe -- FredericS@msn.com
Saturday, May 18, 1996

>Environment: VC++ 4.1 / Win 95
>
>Task: In order to let the user use the scrollbars when a MDI-Childf gets
>out of the client-area of the MDIFrame, I want the latter to support
>Scrollbars.
>
>My (wrong) solution: In my CMDIFrameWnd-derived class, I set the
>Scrollbar-Styles as follows:
>
>BOOL CMyownMDIFrameWnd::PreCreateWindow(CREATESTRUCT& cs)
>	...
>    cs.dwExStyle |= WS_VSCROLL | WS_HSCROLL;
>	...

Well, as WS_HSCROLL and WS_VSCROLL aren't extended styles, you'd better modify 
the standard style :
	cs.style |= WS_VSCROLL | WS_HSCROLL;

Even this way, I don't know if you'll get the expected result so easily.

Frederic Steppe (frederics@msn.com)

---

Amir Salzberg -- amirfalz@netvision.net.il
Sunday, May 19, 1996


you have to take care of OnHScroll() and OnVScroll() yourself; like this:
BOOL DetailDlg::OnInitDialog()
{
	CDialog::OnInitDialog();
	
	// TODO: Add extra initialization here
	SetScrollRange (SB_HORZ, 0, 10);
	SetScrollRange (SB_VERT, 0, 135);
	return TRUE;  // return TRUE  unless you set the focus to a control
}

void DetailDlg::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
	// TODO: Add your message handler code here and/or call default
	// Scroll the dialog box when needed	
	CDialog::OnVScroll(nSBCode, nPos, pScrollBar);
	int pos,gap;
	pos = GetScrollPos(SB_VERT);
	switch (nSBCode) {
	case SB_THUMBPOSITION:
		SetScrollPos (SB_VERT, nPos);
		break;
	case SB_LINEUP:
		gap = 15;
		if (pos - gap > 0) {
		pos -= gap;
		} else {
		pos = 0;
		}
		SetScrollPos (SB_VERT, pos);
		if (pos > 0)
 		   ScrollWindow(0, 15);
		break;
	case SB_LINEDOWN:
		gap = 15;
		if (pos + gap < 135) {
  		   pos += gap;
		} else {
		  pos = 135;
		}
		SetScrollPos (SB_VERT, pos);
		if (pos < 135)
     	   ScrollWindow(0, -15);
		}
}

void DetailDlg::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
	// TODO: Add your message handler code here and/or call default
	// Scroll the dialog box when needed	
	
	CDialog::OnHScroll(nSBCode, nPos, pScrollBar);
	int pos,gap;
	pos = GetScrollPos(SB_HORZ);
	switch (nSBCode) {
	case SB_THUMBPOSITION:
		SetScrollPos (SB_HORZ, nPos);
		break;
	case SB_LINELEFT:
		gap = 1;
		if (pos - gap > 0) {
		pos -= gap;
		} else {
		pos = 0;
		}
		SetScrollPos (SB_HORZ, pos);
		if (pos > 0)
 		   ScrollWindow(1, 0);
		break;
	case SB_LINERIGHT:
		gap = 1;
		if (pos + gap < 10) {
  		   pos += gap;
		} else {
		  pos = 10;
		}
		SetScrollPos (SB_HORZ, pos);
		if (pos < 10)
     	   ScrollWindow(-1, 0);
		}

---

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