Picture Control background is gray and I want it w

问题:

My application has a picture control, whose background is gray and I want it to be white. I already tried several things, like: derive a class and override OnPaint method; respond to WM_CTLCOLOR message (adding ON_WM_CTLCOLOR()and processing it), but no success.

Entry on Message map:

ON_WM_CTLCOLOR()

Implementation:

BOOL CMyDialog::OnInitDialog()
{
    __super::OnInitDialog();

    white.CreateSolidBrush(RGB(255,255,255));

    //...

    return TRUE;  // return TRUE  unless you set the focus to a control
}


HBRUSH CMyDialog::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
    if (pWnd == GetDlgItem(IDC_PICTURE))
    {
        return white;
    }

    return __super::OnCtlColor(pDC, pWnd, nCtlColor);
}

Header file class definition:

CBrush white;

HBRUSH OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor);

回答1:

After some debugging using Spy++, I've realized the Picture Control is a Static Control and the message I have to process is not WM_CTLCOLOR but WM_CTLCOLORSTATIC

So, on the dialog that contains it I changed the message map from

ON_WM_CTLCOLOR()

to

ON_MESSAGE(WM_CTLCOLORSTATIC, OnCtlColorStatic)

---

On the implementation, change the method from

HBRUSH CMyDialog::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
    if (pWnd == GetDlgItem(IDC_PICTURE))
    {
        return white;
    }

    return __super::OnCtlColor(pDC, pWnd, nCtlColor);
}

to

LRESULT CMyDialog::OnCtlColorStatic(WPARAM wParam, LPARAM lParam)
{
    HWND hWnd = (HWND)lParam;

    if (::GetDlgCtrlID(hWnd) == IDC_PICTURE)
        return (LRESULT)white.GetSafeHandle();

    return DefWindowProc(WM_CTLCOLORSTATIC, wParam, lParam);
}

---

And in the header file, change also the method from

HBRUSH OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor);

to

LRESULT OnCtlColorStatic(WPARAM wParam, LPARAM lParam);

---

Notice a subtle difference: the old one worked by returning the HBRUSH brush handle directly; the new one expects a function returning a LRESULT typed variable, so the cast.

The result is what I was expecting:

UPDATE: I recently needed to do a thing where I had to set the Text Color of a Static and discovered that I can get its device context also:

HDC hDC= (HDC)wParam;
HWND hWnd = (HWND)lParam;

So, after I could easily do it by:

SetBkMode(hDC, TRANSPARENT);
SetTextColor(hDC, RGB(0,127,127));