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L_VecSetEventCallback

Summary

Sets a new vector event callback.

Syntax

#include "ltvkrn.h"

L_LVKRN_API L_INT L_VecSetEventCallback(pVector, pProc, pUserData, pOldProc, pOldUserData)

Parameters

pVECTOREVENTPROC pProc

Your callback function that supplies the information that LEADTOOLS needs when handling events. The callback function must adhere to the syntax specified in VECTOREVENTPROC.

L_VOID * pUserData

Void pointer that you can use to pass one or more additional parameters that the callback function needs.

To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure.

If the additional parameters are not needed, you can pass NULL in this parameter.

ppVECTOREVENTPROC pOldProc

Pointer to a pointer to a VECTOREVENTPROC that will be updated with the old callback function.

L_VOID **pOldUserData

Pointer to the additional data used by the old callback function.

Returns

Value	Meaning
SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

For information about the types of events the vector handle can generate, refer to the VECTOREVENT structure.

Required DLLs and Libraries

LTVKRN
For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Example

This example will disable L_VecSetRotation.

#define VECTOR_ERROR_USERNOROTATION    -20000 
 
typedef struct tagDATA 
{ 
   pVECTOREVENTPROC  pOldProc; 
   L_VOID*           pOldUserData; 
} 
DATA, *LPDATA; 
 
L_INT EXT_CALLBACK VectorEventProc(pVECTORHANDLE   pVector, 
                                   L_UINT          uLevel, 
                                   pVECTOREVENT    pEvent, 
                                   L_VOID*         pUserData) 
{ 
   L_INT    nRet; 
   LPDATA   pData; 
 
   pData = (LPDATA) pUserData; 
 
   if (pData->pOldUserData != NULL) 
   { 
      /* call the old event handler */ 
      nRet = pData->pOldProc( pVector, uLevel, pEvent, pData->pOldUserData ); 
      if( nRet != SUCCESS ) 
         return nRet; 
   } 
 
   /* disable rotation */ 
   if( uLevel == 0 &&                                 /* top level event */ 
       pEvent->uType == VECTOR_EVENT_ROTATION &&      /* from a L_VecSelectObject call */ 
       pEvent->Status == VECTOR_EVENT_STATUS_BEFORE ) /* before any action is taken */ 
      return VECTOR_ERROR_USERNOROTATION; 
 
   return SUCCESS; 
} 
 
L_LTVKRNTEX_API L_INT VecSetEventCallbackExample(pVECTORHANDLE pVector) 
{ 
   LPDATA pData; 
 
   /* set a new vector event callback */ 
   pData = (LPDATA) GlobalAllocPtr( GHND, sizeof( LPDATA ) ); 
   pData->pOldProc = NULL; 
   pData->pOldUserData = NULL; 
   return L_VecSetEventCallback( pVector, VectorEventProc, pData, &pData->pOldProc, &pData->pOldUserData ); 
} 
 
L_VOID TestFunction( pVECTORHANDLE pVector ) 
{ 
   L_INT nRet; 
   VECTORPOINT Point; 
 
   /* try to call L_VecSetRotation */ 
   Point.x = 10.0; 
   Point.y = 20.0; 
   Point.z = 30.0; 
   nRet = L_VecSetRotation( pVector, &Point, NULL, NULL, 0L ); 
 
   /* nRet should be VECTOR_ERROR_USERNOROTATION, the value returned from VectorEventProc */ 
}