ScrollHelper.h

// Filename: ScrollHelper.h
// S.Chan, 01 Jul 2005

#ifndef SCROLL_HELPER_INCLUDED
#define SCROLL_HELPER_INCLUDED

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

class CScrollHelper
{
public:
    CScrollHelper();
    ~CScrollHelper();

    // Attach/detach a CWnd or CDialog.
    void   AttachWnd(CWnd* pWnd);
    void   DetachWnd();

    // Set/get the virtual display size. When the dialog or window
    // size is smaller than the display size, then that is when
    // scrollbars will appear. Set either the display width or display
    // height to zero if you don't want to enable the scrollbar in the
    // corresponding direction.
    void   SetDisplaySize(int displayWidth, int displayHeight, double zoomScale);
    const CSize& GetDisplaySize() const;

    // Get current scroll position. This is needed if you are scrolling
    // a custom CWnd which implements its own drawing in OnPaint().
    const CSize& GetScrollPos() const;

    // Get current page size. Useful for debugging purposes.
    const CSize& GetPageSize() const;

    // Scroll back to top, left, or top-left corner of the window.
    void   ScrollToOrigin(bool scrollLeft, bool scrollTop);

    // Message handling.
    void   OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar);
    void   OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar);
    BOOL   OnMouseWheel(UINT nFlags, short zDelta, CPoint pt);
	BOOL   OnMouseHWheel(UINT nFlags, short zDelta, CPoint pt);
    void   OnSize(UINT nType, int cx, int cy);

	BOOL   Update(CPoint changes);

private:
    int    Get32BitScrollPos(int bar, CScrollBar* pScrollBar);
    void   UpdateScrollInfo();
    void   UpdateScrollBar(int bar, int windowSize, int displaySize,
                           LONG& pageSize, LONG& scrollPos, LONG& deltaPos);

    CWnd*  m_attachWnd;
    CSize  m_pageSize;
    CSize  m_displaySize;
    CSize  m_scrollPos;
	double m_zoomScale;
};

#endif // SCROLL_HELPER_INCLUDED

// END