OnPrepareDC

William Drew -- solset@cais.com
Sunday, February 16, 1997


This is from the Remarks section of on-line help for OnPrepareDC:

"Called by the framework before the OnDraw member function is called
for screen display and before the OnPrint member function is called
for each page during printing or print preview. The default
implementation of this function does nothing if the function is called
for screen display. However, this function is overridden in derived
classes, such as CScrollView, to adjust attributes of the device
context; consequently, you should always call the base class
implementation at the beginning of your override."

Some additional information.

1) The class CCnntyPlnView is derived from CScrollView.

2) This is the code in OnInitialUpdate.

void CCnntyPlnView::OnInitialUpdate()
{
 CScrollView::OnInitialUpdate();
 CCnntyPlnDoc* pDoc = GetDocument();
 GetParentFrame()->RecalcLayout();
 CSize mysize(75,75);
 SetScaleToFitSize( mysize );
}

3) The OnDraw code is:
void CCnntyPlnView::OnDraw(CDC* pDC)	   
{
CCnntyPlnDoc* pDoc = GetDocument();

if(!AfxIsValidAddress(pDoc, sizeof(CDocument)))
 return;
if(!AfxIsValidAddress(pDC, sizeof(CDC)))
 return;

CFont* pFont;
m_Font.Detach( );
m_Font.CreatePointFont( 6, (LPCTSTR) "Fixed", pDC);
pDC->SelectObject( m_Font );

CUIObjCore* pObj = pDoc->GridObj();	// could be a cplan or xpdr

if(VALID_ADDR(pObj, CUIObjCore))
{
 if( pObj->IsKindOf(RUNTIME_CLASS(CCnntyPln)))
 {
  CCnntyPln* pCPlan = (CCnntyPln*) pObj;
  DrawCPlan(pDC);
 }
 else if( pObj->IsKindOf(RUNTIME_CLASS(CXpdr)))
 {
   CXpdr* pXpdr = (CXpdr*) pObj;
 }							 
}

pDC->SelectObject( pFont );

if(VALID_ADDR(pFont, CFont))
 pFont->DeleteObject( );
} // end of OnDraw

The OnDraw code works fine until I override OnPrepareDC as shown
below.

void CCnntyPlnView::OnPrepareDC(CDC* pDC, CPrintInfo* pInfo)
{
 CScrollView::OnPrepareDC(pDC, pInfo);
 GetParentFrame()->RecalcLayout();
 CSize mysize(75,75);
 SetScaleToFitSize( mysize );
}

Any direction would be appreciated.

---------------------

William J. Drew
Solution Set, Inc.
solset@cais.com

Environment: VC++ 4.2-flat, NT 4.0

---

Dulepov Dmitry -- dima@ssm6000.samsung.ru
Monday, February 17, 1997

        [Mailer: "Groupware E-Mail". Version 1.03.000]

>        [From: William Drew
>This is from the Remarks section of on-line help for OnPrepareDC:
>
>"...However, this function is overridden in derived
>classes, such as CScrollView, to adjust attributes of the device
>context; consequently, you should always call the base class
>implementation at the beginning of your override."
>
>
>void CCnntyPlnView::OnPrepareDC(CDC* pDC, CPrintInfo* pInfo)
>{
> CScrollView::OnPrepareDC(pDC, pInfo);
> GetParentFrame()->RecalcLayout();
> CSize mysize(75,75);
> SetScaleToFitSize( mysize );
>}
>

1. What the reason to call GetParentFrame()->RecalcLayout() in OnPrepareDC() ? This is a drawing only function. What do you want to do?

2. What do you mean by "The OnDraw code works fine until I override OnPrepareDC as shown
below" ? What do you see on the screen ?



Dmitry A. Dulepov
Samsung Electronics Co., Ltd.
Russian Research Center
Phone: +7 (095) 213-9207
Fax: +7 (095) 213-9196
E-mail: dima@src.samsung.ru
====================================

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