LVectorBase::VectorEventProcCallBack

#include "ltwrappr.h"

virtual L_INT LVectorBase::VectorEventProcCallBack(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 L_FAR * 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.
	Keep in mind that this is a void pointer, which must be cast to the appropriate data type within your callback function.

Returns

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

Comments

To use this function you must derive a class from LVectorBase and override the VectorEventProcCallBack function.

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 LVectorBase::CopyFromClipboard, the toolkit may fire these events in the following sequence:

pEvent->uType	pEvent->Status	uLevel	Comment
VECTOR_EVENT_COPYFROMCLIPBOARD	VECTOR_EVENT_BEFORE	0	LVectorBase::CopyFromClipboard is about to execute.
VECTOR_EVENT_ADDLAYER	VECTOR_EVENT_BEFORE	1	LVectorBase::AddLayer is about to execute.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_BEFORE	2	LVectorBase::AddObject for first object is about to execute.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_AFTER	2	LVectorBase::AddObject for first object has been completed.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_BEFORE	2	LVectorBase::AddObject for second object is about to execute.
VECTOR_EVENT_ADDOBJECT	VECTOR_EVENT_AFTER	2	LVectorBase::AddObject for second object has been completed.
VECTOR_EVENT_ADDLAYER	VECTOR_EVENT_AFTER	1	LVectorBase::AddLayer has been completed.
VECTOR_EVENT_COPYFROMCLIPBOARD	VECTOR_EVENT_AFTER	0	LVectorBase::CopyFromClipboard has been completed.

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

See Also

Functions:	LVectorBase::Event
Topics:	Vector Handle Events

Example

// This example defines a new event consisting of a rotate, translate and a scale.
// A message is displayed in the Event callback before the event and after the event.
// LVectorBase::Event()
// VectorEventProcCallBack
#define MY_CUSTOM_EVENT (VECTOR_EVENT_USER+1)
class LMyVector2: public LVectorBase
{
protected:
   L_INT  LMyVector2::VectorEventProcCallBack(
                           pVECTORHANDLE pVector,
                           L_UINT uLevel,
                           pVECTOREVENT pEvent,
                           L_VOID L_FAR *pUserData
                           );
};

L_INT  LMyVector2::VectorEventProcCallBack(
                           pVECTORHANDLE pVector,
                           L_UINT uLevel,
                           pVECTOREVENT pEvent,
                           L_VOID L_FAR *pUserData
                           )
{
   L_TCHAR *pszMsg= TEXT("");

   if (pEvent->uType == MY_CUSTOM_EVENT)
   {
      switch (pEvent->Status)
      {
      case VECTOR_EVENT_STATUS_BEFORE:
         pszMsg = TEXT("Before MY_CUSTOM_EVENT");
         break;

      case VECTOR_EVENT_STATUS_AFTER:
         pszMsg = TEXT("After MY_CUSTOM_EVENT");
         break;
      }
      MessageBox(NULL, pszMsg, TEXT(""), MB_OK);

   }
   return LVectorBase::VectorEventProcCallBack(pVector, uLevel, pEvent, pUserData);
}

void VectorEventTest( LVectorBase *pVector)
{
   L_INT nRet = SUCCESS;
   VECTOREVENT Event;
   VECTORPOINT Point;

   // Fire our new event, giving all event callbacks in the vector handle a chance to cancel our operation
   memset( &Event, 0, sizeof( Event ) );
   Event.nSize = sizeof( Event );
   Event.uType = MY_CUSTOM_EVENT;

   Event.Status = VECTOR_EVENT_STATUS_BEFORE;
   nRet = pVector->Event(&Event);
   if( nRet != SUCCESS )
   {
      //a callback has returned something other than success, we should cancel
      return;
   }

   // do the operation, for example, rotate, translate and scale

   Point.x = 10.0; Point.y = 20.0; Point.z = 30.0;
   pVector->SetRotation( &Point);

   Point.x = 4.0; Point.y = 4.0; Point.z = 4.0;
   pVector->SetTranslation(&Point );

   Point.x = 0.5; Point.y = 0.5; Point.z = 0.5;
   pVector->SetScale(&Point );

   // notify the vector handle that the operation is done
   Event.Status = VECTOR_EVENT_STATUS_AFTER;
   pVector->Event(&Event );
}