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Event handling

Events of the Fingerprint Scanner

There are two main event sources in the FPS system:

The following programming technics are implemented:

The raised event can be filtered with the event_types property. The event type values are defined in the FPS_EVENT enumeration as well as the event values.

Callback Function

The user implemented callback function have to be registered with the SetEventFunction function. If the capture is started asynchronously by the CaptureStart function, then the callback function is called only during the CaptureStatus or the CaptureWait functions are called. This behaviour can be changed with the async_callback property. Use this property with precaution because user programs might hang up in case of calling Windows functions from an internal capture thread that doesn't own a message queue.
The freerun mode tasks can be called periodically by the user program or an asynchronous background process can be started with the BeginWindowMessaging or StartBGProcesses functions. Currently this kind of event handling is available only in the C/C++ interface.

Window messages

Windows programs can get window messages from the FPS system after a window handle is set by the BeginWindowMessaging function. User programs have to set a range of 32 message ids. The capture events and the freerun mode events both post messages even in asynchronous mode. The message value is base_msg + id, where base_msg is the user defined base offset and id is one of the ids defined in the FPS_WND_MESSAGE enumeration.

ActiveX events

The ActiveX component of the FPS system supports all event types: the FPSEvent event is raised by the capture process, the FingerPresenceEvent , PreviewEvent, ButtonEvent, PowerEvent or ConnectionEvent events are raised by the freerun mode tasks. As the freerun mode events have their individual event methods the event filtering is not applied to them.

Capture events

Freerun mode events


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