VC对话框实现垂直滚动效果

1.修改滚动的范围，设置nMax的值，此处设置为3倍窗口高度。

    CRect rc;
    GetClientRect(&rc);
    SCROLLINFO si = {sizeof(SCROLLINFO)};
    si.fMask = SIF_PAGE | SIF_POS | SIF_RANGE;
    si.nPos = si.nMin = 1;
    si.nMax = rc.Height() * 3;
    si.nPage = rc.Height();
    SetScrollInfo(SB_VERT, &si, FALSE);

2.对话框添加WM_VSCROLL消息响应函数.

    void CPrintDlgAppDlg::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
    {
        SetVScrool(SB_VERT, nSBCode);

        CDialog::OnVScroll(nSBCode, nPos, pScrollBar);
    }

3.代码中添加以下3个辅助函数

    void CPrintDlgAppDlg::ScrollClient(int nBar, int nPos)
    {
        static int s_prevx = 1;
        static int s_prevy = 1;  

        int cx = 0;
        int cy = 0;  

        int& delta = cy;
        int& prev = s_prevy;

        delta = prev - nPos;
        prev = nPos;  

        if(cx || cy)
        {
            ScrollWindow(cx, cy, NULL, NULL);
        }
    }  

    int CPrintDlgAppDlg::GetScrollPos(int nBar, UINT nSBCode)
    {
        SCROLLINFO si;
        si.cbSize = sizeof(SCROLLINFO);
        si.fMask = SIF_PAGE | SIF_POS | SIF_RANGE | SIF_TRACKPOS;
        GetScrollInfo(nBar, &si);  

        const int minPos = si.nMin;
        const int maxPos = si.nMax - (si.nPage - 1);  

        int result = -1;  

        switch(nSBCode)
        {
        case SB_LINEUP /*SB_LINELEFT*/:
            result = max(si.nPos - 1, minPos);
            break;
        case SB_LINEDOWN /*SB_LINERIGHT*/:
            result = min(si.nPos + 1, maxPos);
            break;
        case SB_PAGEUP /*SB_PAGELEFT*/:
            result = max(si.nPos - (int)si.nPage, minPos);
            break;
        case SB_PAGEDOWN /*SB_PAGERIGHT*/:
            result = min(si.nPos + (int)si.nPage, maxPos);
            break;
        case SB_THUMBPOSITION:
            // do nothing
            break;
        case SB_THUMBTRACK:
            result = si.nTrackPos;
            break;
        case SB_TOP /*SB_LEFT*/:
            result = minPos;
            break;
        case SB_BOTTOM /*SB_RIGHT*/:
            result = maxPos;
            break;
        case SB_ENDSCROLL:
            // do nothing
            break;
        }  

        return result;
    }  

    void CPrintDlgAppDlg::SetVScrool(int nBar, UINT nSBCode)
    {
        const int scrollPos = GetScrollPos(nBar, nSBCode);  

        if(scrollPos == -1)
            return;  

        SetScrollPos(nBar, scrollPos, TRUE);
        ScrollClient(nBar, scrollPos);
    }