IAdviseSink::OnDataChange

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Windows Embedded CE 6.0 R3

4/8/2010

This method advises the sink that an object view has changed.

Syntax

void OnDataChange( 
  FORMATETC* pFormatetc, 
  STGMEDIUM* pStgmed
);

Parameters

• pFormatetc
  [in] Pointer to the FORMATETC structure, which describes the following about the calling data object.

  • Format
  • Target device,
  • Rendering
  • Storage information

• pStgmed
  [in] Pointer to the STGMEDIUM structure, which defines the storage medium (global memory, disk file, storage object, stream object, GDI object, or undefined) and ownership of that medium for the calling data object.

Return Value

None.

Remarks

Object handlers and containers of link objects implement OnDataChange to take appropriate steps when notified that data in the object has changed. They also must call IDataObject::DAdvise to set up advisory connections with the objects in whose data they are interested.

For more information on how to specify an advisory connection for data objects, see DAdvise.

Containers that take advantage of OLE's caching support do not need to register for data-change notifications. This is because the information necessary to update the container's presentation of the object, including changes in its data, are maintained in the object's cache.

To determine whether the platform supports this interface, see Determining Supported COM APIs.

Notes to Implementers

If you implement OnDataChange for a container, remember that this method is asynchronous and that making synchronous calls within asynchronous methods is not valid. Therefore, you cannot call IDataObject::GetData to obtain the data you need to update your object.

Instead, either post an internal message, or invalidate the rectangle for the changed data by calling InvalidateRect and waiting for a WM_PAINT message. At this point you can get the data and update the object.

The data itself, which is valid only for the duration of the call, is passed using the storage medium pointed to by pStgmed. Because the caller owns the medium, the advise sink should not free it. Also, if pStgmed points to an IStorage or IStream interface, the sink must not increment the reference count.

Requirements

See Also

Reference

IAdviseSink
FORMATETC
IDataObject::DAdvise
IDataObject::GetData
IStorage
IStream
STGMEDIUM

Concepts

Determining Supported COM APIs

Other Resources

InvalidateRect