Help Version 19.0.2017.10.27
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#include "lttwn.h"
L_INT pEXT_CALLBACK YourFunction (hSession, pUserData);
HTWAINSESSION hSession; |
handle to an existing TWAIN session |
L_VOID * pUserData; |
pointer to additional parameters |
Called for each device event received when acquiring an image from the TWAIN source. The address of this callback is passed as an argument in L_TwainSetDeviceEventCallback.
Parameter |
Description |
hSession |
Handle to an existing TWAIN session. This handle is obtained by calling the L_TwainInitSession or L_TwainInitSession2 or L_TwainInitSession2 function. |
pUserData |
A void pointer that you can use to access a variable or structure containing data that your callback function needs. This gives you a way to receive data indirectly from the function that uses this callback function. (This is the same pointer that you pass in the pUserData parameter of L_TwainSetDeviceEventCallback.) Keep in mind that this is a void pointer, which must be cast to the appropriate data type within your callback function. |
SUCCESS |
The function was successful. |
< 1 |
An error occurred. Refer to Return Codes. |
When the callback is fired, you can call L_TwainGetDeviceEventData function inside it to get the detailed information for the received device event.
To get the CAP_DEVICEEVENT capability values, call L_TwainGetDeviceEventCapability function.
To set the CAP_DEVICEEVENT capability value, call L_TwainSetDeviceEventCapability function.
Required DLLs and Libraries
LTTWN For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files to be Included with your Application. |
Functions: |
L_TwainSetDeviceEventCallback, L_TwainGetDeviceEventData, L_TwainSetDeviceEventCapability, L_TwainGetDeviceEventCapability, L_TwainResetDeviceEventCapability |
Topics: |
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For an example, refer to L_TwainGetDeviceEventData.