CWindowImpl Class

T

Your new class, derived from CWindowImpl.

TBase

The base class of your class. By default, the base class is CWindow.

TWinTraits

A traits class that defines styles for your window. The default is CControlWinTraits.

You can use CWindowImpl to create a window or subclass an existing window. the CWindowImpl window procedure uses a message map to direct messages to the appropriate handlers.

CWindowImpl::Create creates a window based on the window class information that's managed by CWndClassInfo. CWindowImpl contains the DECLARE_WND_CLASS macro, which means CWndClassInfo registers a new window class. If you want to superclass an existing window class, derive your class from CWindowImpl and include the DECLARE_WND_SUPERCLASS macro. In this case, CWndClassInfo registers a window class that's based on an existing class but uses CWindowImpl::WindowProc. For example:

class ATL_NO_VTABLE CMyWindow :
   OtherInheritedClasses
   public CComControl<CMyWindow>
          // CComControl derives from CWindowImpl
{
public:
   // 1. The NULL parameter means ATL will generate a
   //    name for the superclass
   // 2. The "EDIT" parameter means the superclass is
   //    based on the standard Windows Edit box
   DECLARE_WND_SUPERCLASS(NULL, _T("EDIT"))

   // Remainder of class declaration omitted

Note
Because CWndClassInfo manages the information for just one window class, each window created through an instance of CWindowImpl is based on the same window class.

CWindowImpl also supports window subclassing. The SubclassWindow method attaches an existing window to the CWindowImpl object and changes the window procedure to CWindowImpl::WindowProc. Each instance of CWindowImpl can subclass a different window.

Note
For any given CWindowImpl object, call either Create or SubclassWindow. Don't invoke both methods on the same object.

In addition to CWindowImpl, ATL provides CContainedWindow to create a window that's contained in another object.

The base class destructor (~CWindowImplRoot) ensures that the window is gone before the object is destroyed.

CWindowImpl derives from CWindowImplBaseT, which derives from CWindowImplRoot, which derives from TBase and CMessageMap.

CMessageMap

TBase

CWindowImplRoot

CWindowImplBaseT

CWindowImpl

Header: atlwin.h

Reference

Other Resources