Redrawing window to display new message

Posted on 1998-08-25
Last Modified: 2013-11-19
I wish to repaint my window so that the appropriate
message is sent as soon as a flag is set.
My code follows:
void CTextView::OnDraw(CDC* pDC)
      extern int text_out_flag;
      int j;
      CMainDoc* pDoc = GetDocument();

      CRect rect;
      pDC->SetTextAlign(TA_BASELINE | TA_CENTER);
//      pDC->SetTextColor(pDoc->m_colorData);
      // center in the window
      if (!text_out_flag)
            pDC->TextOut(rect.Width() / 2, rect.Height() / 2,
            (LPCTSTR)pDoc->GetLine(0), pDoc->GetStringSize());
      else //if (text_out_flag) //0824
    CMDIChildWnd *pFrame =

            pFrame->InvalidateRect(rect, TRUE);//            pDoc->SwitchView();
/*            pFrame->RedrawWindow(rect, NULL, RDW_VALIDATE | RDW_UPDATENOW | RDW_ERASE);*/
            for (j=0; j<2; j++) {
                  pDC->TextOut(130, (j+2) * 30,
                  (LPCTSTR)pDoc->GetLine(j), strlen (pDoc->m_strData[j]) );

When my text_out_flag is 0, I want one message and when it is set to 1, I want another message on my View.
I have tried Invalidate(), RedrawWindow(), etc to no avail.
Please advice.
Question by:vmehro
1 Comment

Accepted Solution

milenvk earned 50 total points
ID: 1321281
I found some general errors in your code:

1.When text_out_flag is 1 you try to invalidate or redraw the window in the OnDraw() function uncoditionally. In this way you'll end up in an eternal loop. See what happes: if text_out_flag == 1 you invalidate the window, which in turn calls your OnDraw() function which again invalidates the window and so on... Do the invalidation in the place where you change text_out_flag and leave only the drawing functionality in the OnDraw().

2. You invalidate the main frame window, which should invalidate all the children but this will not happen using RedrawWindow() unless you include the RDW_ALLCHILDREN flag.

3. You get the client rectangle of your view and then you use it in the invalidate and redraw functions. The main frame is totally different window and has a rectangle different than the view.

The standard way of handling changes in MFC is when the change occur to call CDocument::UpdateAllViews() function. This will assure proper redraw of all the visible views of the document. And finally in it is a good practice to keep the data in the document. In this way when the data change you can easily handle the change in a document command handler and call CDocument::UpdateAllViews(). In any case avoid having global variables other than theApp since they tend to turn your code into spagetti and they are really against the object oriented idea.

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