MFC Dialog: How to create a non-rectangular dialog box?

[Sonu Kapoor]

Q: How to create a non-rectangular dialog box?

A: The main idea is to use the 'SetWindowRgn()' function. Adding the following lines of code just before the 'return TRUE;' of the 'OnInitDialog()' will produce a dialog box that has rounded corners:

BOOL CYourDialog::OnInitDialog()
{
  CDialog::OnInitDialog();

  // Rest of initialization 
  // ...

  // Create a 'CRgn' object
  CRgn rgn;
  CRect rect;
  GetWindowRect(&rect);
  rgn.CreateRoundRectRgn(0,
                         0,
                         rect.Width(), 
                         rect.Height(),
                         30,
                         30);

  // Set the windows region
  SetWindowRgn(static_cast<HRGN>(rgn.GetSafeHandle()), TRUE);

  // Detach the 'CRgn' object from the region or else the
  // 'CRgn' destructor would close the 'HRGN' handle when 'rgn'
  // goes out of scope
  rgn.Detach(); 

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

You can use a region of any shape that fits into your dialog rect.