New Classes

ATL 2.1 includes 39 new classes, which can be categorized as follows:

IUnknown Implementation	UI Support
Class Factories	Persistence
Thread Pooling	Properties and Property Pages
Threading Models	Data Transfer
Connection Points	Object Safety
Controls	Running Objects
Windows Support	Site Information

IUnknown Implementation

CComObjectRootEx Manages reference counting for both aggregated and nonaggregated objects, and allows you to specify a threading model. CComObjectRoot, defined through a typedef statement, uses the default threading model of the server:
```
typedef CComObjectRootEx<CComObjectThreadModel> 

        CComObjectRoot;
```
CComPolyObject Implements IUnknown for aggregated and nonaggregated objects. Using CComPolyObject avoids having both CComAggObject and CComObject in your module. A single CComPolyObject object handles both aggregated and nonaggregated cases.

Class Factories

Thread Pooling

CComAutoThreadModule Implements an EXE module, with support for multiple thread-pooled apartments.
CComApartment Manages an apartment in a thread-pooled EXE module.
CComSimpleThreadAllocator Manages thread selection for an EXE module.

Threading Models

CComMultiThreadModelNoCS Provides thread-safe methods for incrementing and decrementing a variable. Does not provide a critical section.

Connection Points

IPropertyNotifySinkCP Implements a connection point representing the IPropertyNotifySink interface.
CFirePropNotifyEvent Notifies a client's sink that an object's property has changed or is about to change.

Controls

CComControl Consists of helper functions and data members that are essential to ATL controls.
IOleControlImpl Provides methods necessary for controls.
IOleObjectImpl Provides the principal methods through which a container communicates with a control. Manages the activation and deactivation of in-place controls.
IQuickActivateImpl Combines initialization into a single call to help containers avoid delays when loading controls.
IPointerInactiveImpl Provides minimal mouse interaction for an otherwise inactive control.

Windows Support

CWindow Contains methods for manipulating a window. CWindow is the base class for CWindowImpl, CDialogImpl, and CContainedWindow.
CWindowImpl Implements a window based on a new window class. Also allows you to subclass or superclass the window.
CDialogImpl Implements a dialog box.
CContainedWindow Implements a window contained within another object. Allows you to subclass or superclass the window.
CWndClassInfo Manages the information of a new window class.
CDynamicChain Supports dynamic chaining of message maps.
CMessageMap Allows an object to expose its message maps to other objects.

UI Support

IOleObjectImpl Provides the principal methods through which a container communicates with a control. Manages the activation and deactivation of in-place controls.
IOleInPlaceObjectWindowlessImpl Manages the reactivation of in-place controls. Enables a windowless control to receive messages, as well as to participate in drag and drop operations.
IOleInPlaceActiveObjectImpl Assists communication between an in-place control and its container.
IViewObjectExImpl Enables a control to display itself directly and to notify the container of changes in its display. Provides support for flicker-free drawing, non-rectangular and transparent controls, and hit testing.

Persistence

IPersistStreamInitImpl Allows a client to load and save an object's persistent data to a stream.
IPersistStorageImpl Allows a client to load and save an object's persistent data to a storage.
IPersistPropertyBagImpl Allows a client to load and save an object's properties to a property bag.

Properties and Property Pages

IPropertyPageImpl Manages a particular property page within a property sheet.
IPropertyPage2Impl Similar to IPropertyPageImpl, but also allows a client to select a specific property in a property page.
IPerPropertyBrowsingImpl Accesses the information in an object's property pages.
ISpecifyPropertyPagesImpl Obtains the CLSIDs for the property pages supported by an object.
IPersistPropertyBagImpl Stores an object's properties in a client-supplied property bag.
CComDispatchDriver Retrieves or sets an object's properties through an IDispatch pointer.
CStockPropImpl Implements the stock properties supported by ATL.

Data Transfer

IDataObjectImpl Supports Uniform Data Transfer by using standard formats to retrieve and set data. Handles data change notifications by managing connections to advise sinks.
CBindStatusCallback Allows an asynchronous moniker to send and receive information about the asynchronous data transfer to and from your object.

Object Safety

IObjectSafetyImpl Allows an object to be marked as safe for initialization or safe for scripting.

Running Objects

IRunnableObjectImpl Determines if an object is running, forces it to run, or locks it into the running state.

Site Information

IObjectWithSiteImpl Retrieves and sets a pointer to an object's site. Used for objects that are not controls.
IOleObjectImpl Retrieves and sets a pointer to an object's site. Used for controls.