OnCtrlColor(CDC *pDC, CWnd * pWnd, UINT nCtlColor)参数pWnd的作用

[Luo_Bryant]

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

// TODO: Change any attributes of the DC here

// TODO: Return a different brush if the default is not desired
if(pWnd->GetDlgCtrlID()==IDC_LINE_STYLE)
{
pDC->SetTextColor(RGB(0,255,0));
pDC->SetBkMode(TRANSPARENT);
return m_brush;
}
if(pWnd->GetDlgCtrlID()==IDC_LINE_WIDTH)
{
pDC->SetTextColor(RGB(255,0,0));
// pDC->SetBkMode(TRANSPARENT);
pDC->SetBkColor(RGB(0,0,255));
return m_brush;
}
if(pWnd->GetDlgCtrlID()==IDC_TEXT)
{
pDC->SelectObject(&m_font);
}

if(pWnd->GetDlgCtrlID()==IDOK)
{
pDC->SetTextColor(RGB(255,0,0));
return m_brush;
}
return hbr;
}

为什么直接GetDlgCtrlID()==IDC_LINE_STYLE就不能给对话框中指定的控件改变颜色了呢？？
而要pWnd->GetDlgCtrlID()==IDC_LINE_WIDTH，就搞不懂参数pWnd在这里的作用， GetDlgCtrlID()本身就是 CWnd的函数呀，不是可以直接用的吗，为什么在这里还要加上pWnd-> ？？？

[sumos]

GetDlgCtrlID，你当前所在的是对话框类，这个函数也只是获取对话框的ID。 pWnd就是子控件的指针。

[gfm688]

Since top-level windows do not have an ID value, the return value of this function is invalid if the CWnd is a top-level window.