Cancellation of data transfers in Windows XP

Important

This article contains information that applies to obsolete Windows operating systems.

In Microsoft Windows XP and Windows Me, there were two ways for a WIA application to cancel a data transfer:

• Return S_FALSE from the transfer callback routine, IWiaDataCallback::BandedDataCallback.

• Call IWiaItemExtras::CancelPendingIO. We do not recommend this method and it is not used by any in-box drivers or samples.

There were also two ways for a WIA driver to be notified that the application had canceled a transfer:

• Receive S_FALSE when it called into IWiaMiniDrvCallBack::MiniDrvCallback.

• Receive a call to its IWiaMiniDrv::drvNotifyPnPEvent with a WIA_EVENT_CANCEL_IO event.

One problem with the Windows XP implementation is that there is no connection between the two notification methods; that is, if a user calls IWiaItemExtras::CancelPendingIO but the driver does not support asynchronous canceling of a data transfer through IWiaMiniDrv::drvNotifyPnPEvent, the application will also have to return S_FALSE from IWiaMiniDrvCallBack::MiniDrvCallback.

The IWiaDataCallback and IWiaItemExtras interfaces are described in the Microsoft Windows SDK documentation.