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Responding to System Events During Data Transfer

Prior to Mac OS X, if you want update events to be passed to your application while a dialog box is displayed by the functions URLSimpleDownload, URLDownload, URLSimpleUpload, and URLUpload, you should write your own system event callback function. (In Mac OS X, this is not necessary, since all dialog boxes are moveable). In order for these functions to display a dialog box, you must set the mask constant kURLDisplayProgressFlag or kURLDisplayAuthFlag in the bitmask passed in the openFlags parameter. If you write your own callback to handle update events in these dialog boxes, you should pass a Universal Procedure Pointer (UPP) to your callback in the eventProc parameter of these functions. Call the function NewURLSystemEventUPP to create a UPP to your callback function.

If you do not create a callback function to handle update events when a dialog box is displayed, these functions will display a nonmovable modal dialog box when warranted.

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