HBRUSH data member initialization in OnInitDialog()

I have instructions to declare data members of type HBRUSH and then initialize them in OnInitDialog(). Then I should use these data members in HBRUSH CMyDialog::OnCtlColor(...) so I can change the background color and control colors for my dialog. My questions is: What does it mean to initialize the HBRUSH data members in OnInitDialog()? Thanks in advance.

When you declare data member of type HBRUSH you don't create a brush itself. In OnInitDialog you must create a brush using brush-creating functions like CreateBrushIndirect, CreateSolidBrush etc.
You can think about HBRUSH as about pointer - initially it's null and it will be null until you create a brush (analog of 'new' for pointers).
And like with pointers you must also destroy brush when you dialog is about to die (analog of 'delete' for pointers).



Good luck
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Here are my notes on WM_CTLCOLOR. I use CBrush
instead of HBRUSH.

Here is a method for changing the text and/or background
color of some controls using the WM_CTLCOLOR message.
(edit,static,listbox,radio button,check button,dialog).
See WM_CTLCOLOR for more details.

1) add member variables for the dialog :


COLORREF m_textColor;
COLORREF m_backColor;
CBrush m_backBrush;





2) initialize in OnInitDialog() :


m_textColor = RGB(255,0,0);
m_backColor = RGB(192,192,0);
m_backBrush.CreateSolidBrush(m_backColor);




3) process WM_CTLCOLOR message for dialog :


HBRUSH CTestDialogDlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);

// TODO: Change any attributes of the DC here

//
// note to change ALL the edit boxes, and not
// just one, the if statement below would be :
//
// if (nCtlColor == CTLCOLOR_EDIT)
//
// see WM_CTLCOLOR for more details
//
if (pWnd->GetDlgCtrlID() == IDC_EDIT1)
{
pDC->SetTextColor(m_textColor);
pDC->SetBkColor(m_backColor);
return (HBRUSH)m_backBrush.GetSafeHandle();
}

// TODO: Return a different brush if the default is not desired
return hbr;
}




4) if at some time you want to change the colors,
code it like this :


m_textColor = RGB(255,255,0);
m_backColor = RGB(0,0,255);
m_backBrush.DeleteObject(); // delete old brush
m_backBrush.CreateSolidBrush(m_backColor); // and create new one
GetDlgItem(IDC_EDIT1)->Invalidate(); // force redraw of control





5) note : if you sub-class CEdit, you can do the
above in the derived class itself (process =WM_CTLCOLOR).
That way you do not have to check for the correct control ID.
Just be sure to return a non-NULL brush or the parent will
override the color.

Thanks for your help :)

Thanks so much :)