Re: Inheritance and MFC

From:

"Nobody" <Nobody@yahoo.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 3 Jul 2007 17:30:28 -0700

Message-ID:

<uKMwHKdvHHA.4688@TK2MSFTNGP04.phx.gbl>

Hi Joe,

Why is a grid object not derived from CWnd in the first place?

I wanted to make the grid object independent of MFC.
The only reason I am using CObject is for Serialization.
I am using the registry and a few other MFC functions, OnDraw(), =
OnMouseMove(), etc.
I should actually make several layers, but it is what it is for now.

I noticed that the more I use the grid object, the more I have to keep =
adding scroll bars for pan, zoom, etc.
So, my idea was to make a CWnd GridSB Class that implements Scrollbars.
That class inherits from the Grid CObject class.
Then, I can leave the scroll bars inside of the CGrid Object, instead of =
Creating scroll bars each time.

This is basically what I have.

CGrid : public CObject

CGridSB: public CGrid, public CWnd
{
    CScrollbar sb;
    CreateScrollbars();
    SetScreenRect(){ Position Scrollbars(); }
}

CView::OnDraw()
{
    CGridSB sb;
    sb.SetScreenRect(Rect);
    sb.OnDraw(pDC);
}

Regards,
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message =
news:hndk83t2i52oo7o21fhrt0jpj8f5vn97u7@4ax.com...

Multiple inheritance is chancy in MFC. At least one rule is the CWnd =

class must be the

first class. But in this case, I don't see how a visible object like =

a grid could *not*

derive directly from CWnd, and since CWnd derives from CObject, there =

is no need for the

inheritance from CObject in the first place.

Why is a grid object not derived from CWnd in the first place?
joe
On Tue, 3 Jul 2007 02:49:21 -0700, "Nobody" <Nobody@yahoo.com> wrote:

Hi,

I have a grid object. The Grid Object inherits from CObject.
There are no controls and I was thinking about adding some. Zoom, Pan, =

etc.

So, I have extantiated a new class that inherits from CGrid and CWnd.
class CGridSB : public CGrid, public CWnd

Now, I would like to add some controls to the Grid Object.
The problem is that the controls needs an m_hWnd
I am not sure what to do?

VERIFY(c_sbHZoom.Create(
     SBS_VERT | SBS_RIGHTALIGN | WS_CHILD |WS_BORDER,
  Rect,
  this,
  1234)
);

_AFXWIN_INLINE void CScrollBar::ShowScrollBar(BOOL bShow)
{ ASSERT(::IsWindow(m_hWnd)); ::ShowScrollBar(m_hWnd, SB_CTL, bShow); =

}

I understand that the CGridSB oject needs to handle the Scrollbar =

messages, so I need a message map

and perphaps a DECLARE_DYNCREATE along with an IMPLEMENT_DYNCREATE =

member.

I just need to get past the m_hWnd error.

Thanks for your help,

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm