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Implementation Callbacks for Non-Self-installing Plug-ins (COM API)

COM Callbacks for Custom Events

To use the XSIOnEvent callback function to declare your event handler (COM API)

This is the simplest way to handle events: you need to provide an external DLL or SO that includes the XSIOnEvent function containing a case for each bound event:

HRESULT WINAPI XSIOnEvent
(
   LONG        in_lEventID,
   LPVARIANT   in_pVar,
   LONG        in_lNum
)
{
   switch (in_lEventID)
   {
       case siOnBeginSceneSave:
       {
          if (!CanSaveMyCurrentScene())
          {
              // abort the operation using the predefined abort argument
              LPVARIANT pVar = V_VARIANTREF(&in_pVar[1]);
              V_BOOL(pVar) = VARIANT_TRUE;
          }
       }
       break;
   };
   return S_OK;
}

The XSIOnEvent callback function takes these arguments:

It returns an HRESULT with one possible value:

To abort the operation, set the Abort argument to TRUE. The position of this argument in the argument array is specific to the event itself. For more information, see the Programmer’s Reference section of the Reference guide.

Not all events support an Abort argument. For example, OnTerminate cannot be interrupted.

COM Callbacks for Custom Commands

To use the XSIOnCommand callback function to declare your command handler (COM API)

The XSIOnCommand callback function takes these arguments:

It returns an HRESULT with one possible value:

Don’t forget to export any command handler function you may have defined in your DLL or SO library file. For more information, see Exporting Entry Points, Event And Command Handlers.

Exporting Entry Points, Event And Command Handlers

As is the case with developing any compiled COM function as part of a plug-in for XSI, you need to export the functions that need to be available to XSI with a DEF file so that XSI can find it.

To export your operator entry points with a DEF file

- Specify a a DEF file similar to this one:

   LIBRARY MYFUNC
   DESCRIPTION "COM Operator."
   EXPORTS
       ComSplatter_Update @1 PRIVATE
       ComSplatter_Init @2 PRIVATE
       ComSplatter_Term @3 PRIVATE

Remember that for calling callback functions, XSI uses the name of the function, not its ordinal value.

To export your event handler function

- Specify a a DEF file similar to this one:

   LIBRARY MYHNDL
   DESCRIPTION "Event handler function."
   EXPORTS
       XSIOnEvent @1 PRIVATE

To export your command handler function

- Specify a a DEF file similar to this one:

   LIBRARY MYHNDL
   DESCRIPTION "Command handler function."
   EXPORTS
       XSIOnCommand @1 PRIVATE

XSIOnCommand and XSIOnEvent need to be exported only if they are defined in the .dll.

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