nodeMessageCmd/nodeMessageCmd.cpp

//-
// ==========================================================================
// Copyright 1995,2006,2008 Autodesk, Inc. All rights reserved.
//
// Use of this software is subject to the terms of the Autodesk
// license agreement provided at the time of installation or download,
// or which otherwise accompanies this software in either electronic
// or hard copy form.
// ==========================================================================
//+

//
// nodeMessageCmd.cc
//
// Description:
//     Sample plug-in that demonstrates how to register/de-register
//     a callback with the MNodeMessage class.
//
//     This plug-in will register a new command in maya called
//     "nodeMessage" which adds a callback for the all nodes on
//     the active selection list. A message is printed to stdout 
//     whenever a connection is made or broken for those nodes.
//
#include <maya/MIOStream.h>
#include <maya/MPxCommand.h>
#include <maya/MFnPlugin.h>
#include <maya/MArgList.h>
#include <maya/MIntArray.h>
#include <maya/MSelectionList.h>
#include <maya/MGlobal.h>
#include <maya/MPlug.h>
#include <maya/MNodeMessage.h>
#include <maya/MCallbackIdArray.h>

// This table will keep track of the registered callbacks
// so they can be removed when the plug-ins is unloaded.
//
MCallbackIdArray callbackIds;

//
// Callback function
//
//    Prints out plug information when connections are made or broken.
//    See MNodeMessage.h for all of the available AttributeMessage types.
//

void userCB( MNodeMessage::AttributeMessage msg, MPlug & plug,
             MPlug & otherPlug, void* )
{
    if ( msg & MNodeMessage::kConnectionMade ) {
        cout << "Connection made ";
    } else if ( msg & MNodeMessage::kConnectionBroken ) {
        cout << "Connection broken ";
    } else {
        return;
    }
    cout << plug.info();
    if ( msg & MNodeMessage::kOtherPlugSet ) {
        if ( msg & MNodeMessage::kIncomingDirection ) {
                cout << "  <--  " << otherPlug.info();
        } else {
                cout << "  -->  " << otherPlug.info();
        }
    }
    cout << endl;
}

//
// Command class declaration
//

class nodeMessageCmd : public MPxCommand
{
public:
                    nodeMessageCmd() {};
                ~nodeMessageCmd() override; 
    MStatus         doIt( const MArgList& args ) override;
    static void*    creator();
};

//
// Command class implementation
//

nodeMessageCmd::~nodeMessageCmd() {}

void* nodeMessageCmd::creator()
{
    return new nodeMessageCmd();
}

MStatus nodeMessageCmd::doIt( const MArgList& )
//
// Takes the  nodes that are on the active selection list and adds an
// attriubte changed callback to each one.
//
{
    MStatus         stat;
    MObject         node;
    MSelectionList  list;
    MCallbackId     id;
    
    // Register node callbacks for all nodes on the active list.
    //
    MGlobal::getActiveSelectionList( list );

    for ( unsigned int i=0; i<list.length(); i++ )
    {
        list.getDependNode( i, node );
        
        id = MNodeMessage::addAttributeChangedCallback( node,
                                                        userCB,
                                                        NULL,
                                                        &stat);

        // If the callback was successfully added then add the
        // callback id to our callback table so it can be removed
        // when the plugin is unloaded.
        //
        if ( stat ) {
            callbackIds.append( id );
        } else {
            cout << "MNodeMessage.addCallback failed\n";
        }
    }
        
    return stat;
}

//
// Plugin registration
//

MStatus initializePlugin( MObject obj )
{
    MFnPlugin plugin( obj );
    return plugin.registerCommand( "nodeMessage", nodeMessageCmd::creator );
}

MStatus uninitializePlugin( MObject obj)
{
    // Remove all callbacks
    //
    for (unsigned int i=0; i<callbackIds.length(); i++ ) {
        MMessage::removeCallback( (MCallbackId)callbackIds[i] );
    }

    MFnPlugin plugin( obj );
    return plugin.deregisterCommand( "nodeMessage" );
}