VECTOREVENTPROC Function

#include "lvkrn.h"

L_INT pEXT_CALLBACK YourFunction (pVector, uLevel, pEvent, pUserData)

pVECTORHANDLE pVector;	pointer to a vector handle
L_UINT uLevel;	event level
pVECTOREVENT pEvent;	pointer to a vector event
L_VOID * pUserData;	pointer to additional parameters

Processes each event that occurs inside the vector handle.

Parameter	Description
pVector	Pointer to the vector handle in which the event occurred.
uLevel	Level of the event that occurred. For a top-level event, this value is 0. For a second level event this value is 1, etc. For an example, refer to the Comments section below.
pEvent	Pointer to a VECTOREVENT structure that describes the event that occurred in the vector handle.
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 passed in L_VecSetEventCallback.)
	Keep in mind that this is a void pointer, which must be cast to the appropriate data type within your callback function.

Returns

The return value is valid only when pEvent->Status is EVENT_STATUS_BEFORE.

SUCCESS	Continue with the operation.
SUCCESS_ABORT	Abort this operation only.
< 1	An error occurred. Refer to Return Codes.

Comments

To understand event levels, consider this example:

Assume the clipboard contains a vector handle with 1 layer and 2 objects inside this layer.

Now you execute L_VecCopyFromClipboard, the toolkit may fire these events in the following sequence:

pEvent->uType	pEvent->Status	uLevel	Comment
VECTOR_EVENT_COPYFROMCLIPBOARD	VECTOR_EVENT_BEFORE	0	L_VecCopyFromClipboard is about to execute.
VECTOR_EVENT_ADDLAYER	VECTOR_EVENT_BEFORE	1	L_VecAddLayer is about to execute.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_BEFORE	2	L_VecAddObject for first object is about to execute.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_AFTER	2	L_VecAddObject for first object has been completed.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_BEFORE	2	L_VecAddObject for second object is about to execute.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_AFTER	2	L_VecAddObject for second object has been completed.
VECTOR_EVENT_ADDLAYER	VECTOR_EVENT_AFTER	1	L_VecAddLayer has been completed.
VECTOR_EVENT_COPYFROMCLIPBOARD	VECTOR_EVENT_AFTER	0	L_VecCoptFromClipboard has been completed.

Your callback can monitor all these operations and cancel whatever operation you want.

Returning SUCCESS_ABORT will abort a single operation. For example, to delete objects and not the layers of a vector when L_VecEmpty is called, the callback can be written like this:

L_INT VectorEventCallback( pVECTOREVENT pEvent ) 
{ 
   switch( pEvent->uType ) 
   { 
      case VECTOR_EVENT_DELETEOBJECT: 
      if( pEvent->Status == VECTOR_EVENT_STATUS_BEFORE ) // a chance to cancel 
      { 
         return SUCCESS_ABORT; // cancel this operation only, continue with the rest 
      } 
      break; 
default: 
      break; 
   } 
   return SUCCESS; 
}

Required DLLs and Libraries

LVKRN

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

For an example, refer to L_VecSetEventCallback.

Help Version 19.0.2017.10.27

LEADTOOLS Vector C API Help

Introduction

Version History

LEADTOOLS Vector Features

Redistributables/Files To Be Included With Your Application