Visual C++ and MFC Programming 2nd Edition

Chapter 15: Fundamental Controls Visual C++ and MFC Fundamentals

happen. In the same way, when this method is called with the SW_HIDE argument, the

control would be hidden, whether it was already hidden or not.

If you want to check the visibility of a control before calling the ShowWindow() method,

you can call the CWnd::IsWindowVisible() method. Its syntax is:

BOOL IsWindowVisible() const;

This method returns TRUE if the control that called it is already visible. If the control is

hidden, the method returns FALSE.

14.2.10The Window’s Availability...............................................................

We saw that when a control has been created, it is available to the user who can interact

with its value. This is because a control usually has its Disable property to False or

unchecked. A control is referred to as disabled if the user can see it but cannot change its

value.

If for any reason a control is disabled, to enable it, you can call the

CWnd::EnableWindow() method. In fact, the EnableWindow() method is used either

to enable or to disable a window. Its syntax is:

BOOL EnableWindow(BOOL bEnable = TRUE);

Here is an example that disables a control called Memo:

void CSecondDlg::OnDisableMemo()

{

// TODO: Add your control notification handler code here

Memo->EnableWindow(FALSE);

}

When calling the EnableWindow() method, if you pass the FALSE value, the control is

disabled, whether it was already disabled or not. If you pass the TRUE constant, it gets

enabled even it was already enabled. Sometimes you may want to check first whether the

control is already enabled or disabled. This can be accomplished by calling the

CWnd::IsWindowEnabled(). Its syntax is:

BOOL IsWindowEnabled( ) const;

This method checks the control that called it. If the control is enabled, the member

function returns TRUE. If the control is disabled, this method returns FALSE. Here is an

example:

void CSecondDlg::OnDisableMemo()

{

// TODO: Add your control notification handler code here

if( Memo->IsWindowEnabled() == TRUE )

Memo->EnableWindow(FALSE);

else // if( !Memo->IsWindowEnabled() )

Memo->EnableWindow();

}

Here is a simplified version of the above code: