Re: problem in using CPaintDC

From:

bruceminoo@hotmail.com

Newsgroups:

microsoft.public.vc.mfc

Date:

10 Jun 2006 16:22:02 -0700

Message-ID:

<1149981722.754339.316120@u72g2000cwu.googlegroups.com>

David Wilkinson wrote:

bruceminoo@hotmail.com wrote:

Hi

I am trying to change a piece of code that ran in CClientDC into
CPaintDC on VC 6.

I have tried using ...

//win32 app
// needs multi threading

#include <afxwin.h>

XxXxXx removed original query

XxXxXx end block removed original query

MyApp theApp;

....
It compiles but does exactly nothing

Could someone please tell me what I am doing wrong

Thanks
Bruce

Bruce:

1. CPaintDC should be used only in the OnPaint() handler.

2. All painting should be done in OnPaint().

3. The correct way to trigger a paint event is to call Invalidate() or
InvalidateRect().

David Wilkinson

David,

Thank your for your interest in replying to me

I think I have impliemented your suggestions but I cant trigger an
invalidate

You can see the different attempts that I have made

Can you please advise what I have done wrong

thanks
Bruce

======== updated code follows

//win32 app
// needs multi threading

#include <afxwin.h>

class A_Std_Window :public CFrameWnd
{
    CPoint m_StartPoint, m_EndPoint;
    public:
    A_Std_Window()
    {
         Create(NULL,"put window title here");
    }
    void OnLButtonUp();
    void OnPaint();
    DECLARE_MESSAGE_MAP()
};

void A_Std_Window::OnPaint()
{
    AfxMessageBox("in on paint",MB_ICONEXCLAMATION|MB_YESNOCANCEL);
    m_StartPoint.x=40;
    m_StartPoint.y=50;

m_EndPoint.x=4;
    m_EndPoint.y=5;

    CPaintDC dc(this); //paint here

    dc.MoveTo(m_StartPoint);
    dc.LineTo(m_EndPoint);

    dc.FillSolidRect(0,0,40,40, RGB(255,0,0));

    CRect rect; // Create a CRect object
    GetClientRect(rect); // Retrieve the view's rectangle into the rect
object

    // Draw the text in the middle of the view
    dc.DrawText(_T("hello"), rect, DT_CENTER | DT_VCENTER |
DT_SINGLELINE);
// dc.DrawText(m_strText, rect, DT_CENTER | DT_VCENTER |
DT_SINGLELINE);

}

BEGIN_MESSAGE_MAP( A_Std_Window, CFrameWnd)
    ON_WM_LBUTTONUP() //Macro to map the left button click to the
handler
END_MESSAGE_MAP()

void A_Std_Window::OnLButtonUp()
{
     // TODO: Add your message handler code here and/or call default

    m_StartPoint.x=40;
    m_StartPoint.y=50;

m_EndPoint.x=4;
    m_EndPoint.y=5;
    AfxMessageBox("heading for
invalidated",MB_ICONEXCLAMATION|MB_YESNOCANCEL);
// Invalidate(TRUE); // invalidate trigger OnPaint one of them should
work
// Invalidate(NULL);
// Invalidate(FALSE);
    Invalidate();
// InvalidateRect(NULL); // sends message
    UpdateWindow(); // force act on message

}

class MyApp :public CWinApp
{
     A_Std_Window *windo; // create a window pointer
     public:
     BOOL InitInstance()
     {
           windo = new A_Std_Window();
           m_pMainWnd = windo;
           m_pMainWnd->ShowWindow(1);
           m_pMainWnd->UpdateWindow();
           return 1;
      }

};

MyApp theApp;