How to enable shadow for Owner Drawn Dialog

Question

I am using owner drawn dialog. I like to give the shadow for my sub-dialog. Is it possible?

Thank in advance.

Answer 1

Sure, it's possible. You could tweak your dialog background using OnEraseBkgnd().

As an example, I have put shadows on the OK and Cancel buttons of a dialog (CDialogControlShadowDlg) ...

First, some declarations in the header file of your dialog class:

// Implementation
protected:
    HICON m_hIcon;

    CRect ComputeDrawingRect(int control_id);   // <-- !!!
    void DrawShadow(CDC* pDC, CRect &r);        // <-- !!!

    // Generated message map functions
    virtual BOOL OnInitDialog();
    afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
    afx_msg void OnPaint();
    afx_msg HCURSOR OnQueryDragIcon();
    afx_msg BOOL OnEraseBkgnd(CDC* pDC);        // <-- !!!
    DECLARE_MESSAGE_MAP()
};

Then add OnEraseBkgnd to your message map in the .cpp file:

BEGIN_MESSAGE_MAP(CDialogControlShadowDlg, CDialog)
    ON_WM_SYSCOMMAND()
    ON_WM_PAINT()
    ON_WM_QUERYDRAGICON()
    ON_WM_ERASEBKGND()          // <-- !!!
    //}}AFX_MSG_MAP
END_MESSAGE_MAP()

Last, but not least, the member function definitions:

// gets the actual drawing location of a control relative to the dialog frame
CRect CDialogControlShadowDlg::ComputeDrawingRect(int control_id)
{
    CRect r;
    GetDlgItem(control_id)->GetWindowRect(&r);
    ScreenToClient(&r);

    return r;
}

#define SHADOW_WIDTH 6  
// draws the actual shadow
void CDialogControlShadowDlg::DrawShadow(CDC* pDC, CRect &r)
{
    DWORD dwBackgroundColor = GetSysColor(COLOR_BTNFACE);
    DWORD dwDarkestColor = RGB(GetRValue(dwBackgroundColor)/2, 
                            GetGValue(dwBackgroundColor)/2,
                            GetBValue(dwBackgroundColor)/2); // dialog background halftone as base color for shadow
    int nOffset;
    for (nOffset = SHADOW_WIDTH; nOffset > 0; nOffset--)
    {
        DWORD dwCurrentColorR = (GetRValue(dwDarkestColor)*(SHADOW_WIDTH-nOffset)
                                 + GetRValue(dwBackgroundColor)*nOffset) / SHADOW_WIDTH;
        DWORD dwCurrentColorG = (GetGValue(dwDarkestColor)*(SHADOW_WIDTH-nOffset)
                                 + GetGValue(dwBackgroundColor)*nOffset) / SHADOW_WIDTH;
        DWORD dwCurrentColorB = (GetBValue(dwDarkestColor)*(SHADOW_WIDTH-nOffset) 
                                + GetBValue(dwBackgroundColor)*nOffset) / SHADOW_WIDTH;
        pDC->FillSolidRect(r + CPoint(nOffset, nOffset), RGB(dwCurrentColorR, dwCurrentColorG, dwCurrentColorB));
    }
}

BOOL CDialogControlShadowDlg::OnEraseBkgnd( CDC* pDC )
{
    // draw dialog background
    CRect rdlg;
    GetClientRect(&rdlg);
    DWORD dwBackgroundColor = GetSysColor(COLOR_BTNFACE);
    pDC->FillSolidRect(rdlg, dwBackgroundColor); 

    // draw shadows
    CRect r1, r2;
    r1 = ComputeDrawingRect(IDOK);
    r2 = ComputeDrawingRect(IDCANCEL);
    DrawShadow(pDC, r1);
    DrawShadow(pDC, r2);

    return TRUE;
}

After applying these modifications, the dialog should look like this:

_{(source: easyct.de)}