something about clipping in OnCustomdraw

From:

".rhavin grobert" <clqrq@yahoo.de>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 10 Oct 2008 09:02:28 -0700 (PDT)

Message-ID:

<7f79780c-080e-44d9-91ec-0ac92fbc26a4@l76g2000hse.googlegroups.com>

hi folks;-)

the following snipped comes from a customdraw-fn in a slider. As you
can see, i draw my own thumb and want to set some text in the control:

____________________________________________________________

class SHTC_API CQSlider : public CSliderCtrl
{
public:
    CQSlider();
    virtual ~CQSlider();

    // ... other stuff ... //

    // set sliders text, may contain '%d' (or %x...) for value
    void QTitleSet(LPCTSTR szTitle);

protected:
    //{{AFX_MSG(CQSlider)
    afx_msg void OnCustomdraw(NMHDR* pNMHDR, LRESULT* pResult);
    //}}AFX_MSG

    DECLARE_MESSAGE_MAP()

private:
    void _DrawThumb(NMCUSTOMDRAW& nmcd);
    void _DrawText(NMCUSTOMDRAW& nmcd);

    CString m_scTitle;
};

//-----------------------------------------------------------------------------
void CQSlider::OnCustomdraw(NMHDR* pNMHDR, LRESULT* pResult)
{
    NMCUSTOMDRAW nmcd = *(LPNMCUSTOMDRAW)pNMHDR;

    switch (nmcd.dwDrawStage)
    {
    case CDDS_PREPAINT:
        *pResult = CDRF_NOTIFYITEMDRAW | CDRF_NOTIFYPOSTPAINT;
        break;

    case CDDS_ITEMPREPAINT:
        switch (nmcd.dwItemSpec)
        {
        case TBCD_TICS:
            *pResult = CDRF_DODEFAULT;
            break;
        case TBCD_THUMB:
            _DrawThumb(nmcd);
            *pResult = CDRF_SKIPDEFAULT;
            break;
        case TBCD_CHANNEL:
            *pResult = CDRF_DODEFAULT;
            break;
        }
        break;

    case CDDS_POSTPAINT:
        _DrawText(nmcd);
        break;

    default:
        *pResult = CDRF_DODEFAULT;
    }
}

//-----------------------------------------------------------------------------
void CQSlider::_DrawText(NMCUSTOMDRAW& nmcd)
{
    CDC* pDC = CDC::FromHandle(nmcd.hdc);

    CRect rcClient;
    GetClientRect(&rcClient);

    CString scText;
    scText.Format(m_scTitle, GetPos());
    pDC->SetBkMode(TRANSPARENT);
    pDC->SelectClipRgn(NULL);
    pDC->DrawText(scText, rcClient, DT_CENTER | DT_BOTTOM |
DT_SINGLELINE);
}

____________________________________________________________

the problem is: first time (initial, get focus), the text is drawn
correctly, but then, when moving the slider, everything except the
thumb gets clipped, so pDC->SelectClipRgn(NULL) seems to dont do
anything at all.

any suggestions welcome,

~.rhavin;)