L_VecSetEventCallback

#include "ltvkrn.h"

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

Sets a new vector event callback.

Parameters

pVECTORHANDLE pVector

Pointer to a vector handle.

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

See Also

Functions

Topics

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 */ 
} 

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