At one paint per second you shouldn't see any flickering, and you shouldn't
need double buffering for something this small.
Well the whole thing comes done to these two functions
Here things look fine except for the fact that you are not unselecting the
font out of the dc.
void CFlickeringCounterView::OnDraw(CDC* pDC)
{
CFlickeringCounterDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;
CFont MyFont;
MyFont.CreatePointFont(240, "Arial");
CFont *pOldFont = pDC->SelectObject(&MyFont);
pDC->TextOut(0, 0, String);
pDC->SelectObject(pOldFont);
}
Here is a different story. You should not user CPaintDC outside of OnPaint.
The font that you are selecting into the dc is going to be destroyed as soon
as OnTimer is over.
So you will end up with a bad font in the device context.
void CFlickeringCounterView::OnTimer(UINT nIDEvent)
{
if (nIDEvent == 1)
{
Counter++;
String.Format("Counter = %i", Counter);
Invalidate();
UpdateWindow();
}
//you don't need these lines.
//CPaintDC TmpDC(this);
//CFont MyFont;
//MyFont.CreatePointFont(240, "Arial");
//TmpDC.SelectObject(&MyFont);
//CSize MySize = TmpDC.GetTextExtent(String);
//CRect MyRect(CPoint(0, 0), CPoint(MySize.cx, MySize.cy));
//InvalidateRect(MyRect);
CView::OnTimer(nIDEvent);
}
I ran this exact same code on my machine without any flickers. I even
increased the font size to 64points. The only time I saw a flicker was when
the timer was set to something smaller than 500ms.
If the flickering still presist you my want to switch to double buffering
where you draw the background and everything else on a memory dc and then
blit the results to the screen in one shot.
AliR.
"C Hill MBSC" <CHillMBSC@discussions.microsoft.com> wrote in message
news:C4D09CC9-745C-4D8D-B7C6-8E60DCDBB1F4@microsoft.com...
Dear All!
I have just written a piece of MFC Code to output a counter value every
second to the screen. Could anyone tell me where I have gone wrong,
because
the text occasionally flickers with white lines through it! It only
happens
occasionally on my machine but is unprofessional! I would like to know
whether there is a problem with MFC, or my code.
P.S. Most of the code was created with AppWizard and message map functions
have been added along with initialisation.
Thank you for your assistance in this matter.
// FlickeringCounterView.cpp : implementation of the
CFlickeringCounterView
class
//
#include "stdafx.h"
#include "FlickeringCounter.h"
#include "FlickeringCounterDoc.h"
#include "FlickeringCounterView.h"
#include ".\flickeringcounterview.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#endif
// CFlickeringCounterView
IMPLEMENT_DYNCREATE(CFlickeringCounterView, CView)
BEGIN_MESSAGE_MAP(CFlickeringCounterView, CView)
// Standard printing commands
ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
ON_WM_TIMER()
ON_WM_CREATE()
END_MESSAGE_MAP()
// CFlickeringCounterView construction/destruction
CFlickeringCounterView::CFlickeringCounterView()
{
// TODO: add construction code here
Counter = 0;
}
CFlickeringCounterView::~CFlickeringCounterView()
{
}
BOOL CFlickeringCounterView::PreCreateWindow(CREATESTRUCT& cs)
{
// TODO: Modify the Window class or styles here by modifying
// the CREATESTRUCT cs
return CView::PreCreateWindow(cs);
}
// CFlickeringCounterView drawing
void CFlickeringCounterView::OnDraw(CDC* pDC)
{
CFlickeringCounterDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;
// TODO: add draw code for native data here
CFont MyFont;
MyFont.CreatePointFont(240, "Arial");
pDC->SelectObject(&MyFont);
pDC->TextOut(0, 0, String);
}
// CFlickeringCounterView printing
BOOL CFlickeringCounterView::OnPreparePrinting(CPrintInfo* pInfo)
{
// default preparation
return DoPreparePrinting(pInfo);
}
void CFlickeringCounterView::OnBeginPrinting(CDC* /*pDC*/, CPrintInfo*
/*pInfo*/)
{
// TODO: add extra initialization before printing
}
void CFlickeringCounterView::OnEndPrinting(CDC* /*pDC*/, CPrintInfo*
/*pInfo*/)
{
// TODO: add cleanup after printing
}
// CFlickeringCounterView diagnostics
#ifdef _DEBUG
void CFlickeringCounterView::AssertValid() const
{
CView::AssertValid();
}
void CFlickeringCounterView::Dump(CDumpContext& dc) const
{
CView::Dump(dc);
}
CFlickeringCounterDoc* CFlickeringCounterView::GetDocument() const //
non-debug version is inline
{
ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CFlickeringCounterDoc)));
return (CFlickeringCounterDoc*)m_pDocument;
}
#endif //_DEBUG
// CFlickeringCounterView message handlers
void CFlickeringCounterView::OnTimer(UINT nIDEvent)
{
// TODO: Add your message handler code here and/or call default
Counter++;
String.Format("Counter = %i", Counter);
CPaintDC TmpDC(this);
CFont MyFont;
MyFont.CreatePointFont(240, "Arial");
TmpDC.SelectObject(&MyFont);
CSize MySize = TmpDC.GetTextExtent(String);
CRect MyRect(CPoint(0, 0), CPoint(MySize.cx, MySize.cy));
InvalidateRect(MyRect);
CView::OnTimer(nIDEvent);
}
int CFlickeringCounterView::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (CView::OnCreate(lpCreateStruct) == -1)
return -1;
// TODO: Add your specialized creation code here
SetTimer(1, 1000, NULL); // 1Hz Counter Timer
return 0;
}
// FlickeringCounterView.h : interface of the CFlickeringCounterView class
//
#pragma once
class CFlickeringCounterView : public CView
{
private:
CString String;
int Counter;
protected: // create from serialization only
CFlickeringCounterView();
DECLARE_DYNCREATE(CFlickeringCounterView)
// Attributes
public:
CFlickeringCounterDoc* GetDocument() const;
// Operations
public:
// Overrides
public:
virtual void OnDraw(CDC* pDC); // overridden to draw this view
virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
protected:
virtual BOOL OnPreparePrinting(CPrintInfo* pInfo);
virtual void OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo);
virtual void OnEndPrinting(CDC* pDC, CPrintInfo* pInfo);
// Implementation
public:
virtual ~CFlickeringCounterView();
#ifdef _DEBUG
virtual void AssertValid() const;
virtual void Dump(CDumpContext& dc) const;
#endif
protected:
// Generated message map functions
protected:
DECLARE_MESSAGE_MAP()
public:
afx_msg void OnTimer(UINT nIDEvent);
afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
};
#ifndef _DEBUG // debug version in FlickeringCounterView.cpp
inline CFlickeringCounterDoc* CFlickeringCounterView::GetDocument() const
{ return reinterpret_cast<CFlickeringCounterDoc*>(m_pDocument); }
#endif
--
Engineering