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IProgressNotify::OnProgress method (objidl.h)

  • Article

Notifies registered objects and applications of the progress of a downloading operation.

Syntax

HRESULT OnProgress(
  [in] DWORD dwProgressCurrent,
  [in] DWORD dwProgressMaximum,
  [in] BOOL  fAccurate,
  [in] BOOL  fOwner
);

Parameters

[in] dwProgressCurrent

The amount of data available.

[in] dwProgressMaximum

The total amount of data to be downloaded.

[in] fAccurate

Indicates the accuracy of the values in dwProgressCurrent and dwProgressMaximum. They are either reliable (TRUE) or unreliable (FALSE). The FALSE value indicates that control structures for determining the actual position of, or amount of, data yet to be downloaded are not available.

[in] fOwner

Indicates whether this OnProgress call can control the blocking behavior of the operation. If TRUE, the caller can use return values from OnProgress to block (STG_S_BLOCK), retry (STG_S_RETRYNOW), or monitor (STG_S_MONITORING) the operation. If FALSE, the return value from OnProgress has no influence on blocking behavior.

Return value

This method can return the standard return values E_FAIL, E_INVALIDARG, E_OUTOFMEMORY, and E_UNEXPECTED, as well as the following values.

Return code Description
STG_S_RETRYNOW
 The caller is to retry the operation immediately. (This value is most useful for applications that do blocking from within the callback routine.)
STG_S_BLOCK
 The caller is to block the download and retry the call as needed to determine if additional data is available. This is the default behavior if no sinks are registered on the connection point.
STG_S_MONITORING
 The callback recipient relinquishes control of the downloading process to one of the other objects or applications that have registered progress notification sinks on the same stream. This is useful if the notification sink is interested only in gathering statistics.
E_PENDING
 Data is currently unavailable. The caller is to try again after some desired interval. The notification sink returns this value if the asynchronous storage is to operate in nonblocking mode.

Remarks

Sinks may be inherited by any substorage or substream of a given storage. If no sink is registered, the thread will block until the requested data becomes available, or the download is canceled by the downloader.

Where multiple objects or applications have registered progress notification sinks on a single stream, only one of them can control the behavior of a download. Ownership of the download goes to the first sink to register with the storage or stream, or any advise skinks that may have been inherited from the parent storage (if the storage was created with ASYNC_MODE_COMPATIBILITY.)

Any one of the sinks can relinquish control to the next connection point by returning STG_S_MONITORING to the connection point making the current caller. After a connection point obtains control (through receiving STG_S_BLOCK or STG_S_RETRYNOW), all subsequent connection points calling OnProgress will set fOwner to FALSE.

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header objidl.h

See also

IProgressNotify