滚动条在mfc应用程序中不起作用

Question

我的mfc应用程序的视图类继承了CSrollView类，因为它可以很容易地支持滚动条。我可以让滚动条出现在某一点，就像我放大视图中显示的东西，但是当我尝试向左滚动时，没有任何反应。我已经在网上研究了几个小时，我无法确定我做错了什么。这是视图类中的OnDraw（）和OnInitialUpdate（）方法：

void CWaveEditView::OnDraw(CDC* pDC)
{
    CWaveEditDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    if (!pDoc)
        return;
// TODO: add draw code for native data here
    WaveFile * wave = &pDoc->wave;

    if (wave->hdr==NULL) {
        return;
    }

    // Get dimensions of the window.
    CRect rect;
    GetClientRect(rect);


    // Set color in pen and brush for wave
    COLORREF color = RGB( 0, 255, 0 );
    CPen pen2( PS_SOLID, 0, color );
    pDC->SelectObject( &pen2 );
    CBrush brush2(color);
    pDC->SelectObject( &brush2 );

     // Draw selection if any
    if (selectionStart != selectionEnd) {
        pDC->Rectangle(selectionStart, 0, selectionEnd, rect.Height());
    }

    // Draw the wave
    pDC->MoveTo(0,0);
    int x;
    for (x=0; x < zoomAmount*wave->lastSample/scaling; x++) {
        // Assuming the whole file will be fit in the window, for every x value in the window
        // we need to find the equivalent sample in the wave file.
        float val = wave->get_sample((int) (x*scaling/zoomAmount) );

        // We need to fit the sound also in the y axis. The y axis goes from 0 in the
        // top of the window to rect.Height at the bottom. The sound goes from -32768 to 32767
        // we scale it in that way.
        int y = (int) ((val+32768) * (rect.Height()-1) / (32767+32768));
        pDC->LineTo(x,rect.Height() - y);
    }
    CSize totalSize;
    totalSize.cx = x;
    SetScrollSizes(MM_TEXT,totalSize);
}

void CWaveEditView::OnInitialUpdate()
{
    CScrollView::OnInitialUpdate();

    // Initial scroll sizes
    CSize sizeTotal;
    CRect rect;
    CWaveEditDoc *doc = GetDocument();
    WaveFile * wave = &doc->wave;
    GetClientRect(rect);
    scaling = wave->lastSample/rect.Width();
    sizeTotal.cx = 700;
    sizeTotal.cy = 700;
    SetScrollSizes(MM_TEXT, sizeTotal);
}