InternetSetStatusCallback


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InternetSetStatusCallback
INTERNET_STATUS_CALLBACK InternetSetStatusCallback(
    IN HINTERNET hInternet,
    IN INTERNET_STATUS_CALLBACK lpfnInternetCallback
);
Sets up a callback function that Win32 Internet functions can call as progress is made during an operation.
Returns the previously defined status callback function if successful, NULL if there was no previously defined status callback function, or INTERNET_INVALID_STATUS_CALLBACK if the callback function is not valid.

hInternet
Handle for which the callback is to be set.
lpfnInternetCallback
Address of the callback function to call when progress is made, or to return NULL to remove the existing callback function. For more information about the callback function, see INTERNET_STATUS_CALLBACK.

Both synchronous and asynchronous functions use the callback function to indicate the progress of the request, such as resolving a name, connecting to a server, and so on. The callback function is required for an asynchronous operation. The asynchronous request will call back to the application with INTERNET_STATUS_REQUEST_COMPLETE to indicate the request has been completed.
A callback function can be set on any handle, and is inherited by derived handles. A callback function can be changed using InternetSetStatusCallback, providing there are no pending requests that need to use the previous callback value. Note, however, that changing the callback function on a handle does not change the callbacks on derived handles, such as that returned by InternetConnect. You must change the callback function at each level.
Many of the Win32 Internet functions perform several operations on the network. Each operation can take time to complete, and each can fail.
It is sometimes desirable to display status information during a long-term operation. You can display status information by setting up an Internet status callback function that cannot be removed as long as any callbacks or any asynchronous functions are pending.
After initiating InternetSetStatusCallback, the callback function can be accessed from within any Win32 Internet function for monitoring time-intensive network operations.

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