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Public Types | Static Public Member Functions

# MNodeMessage Class Reference
OpenMaya - API module for common classes

This reference page is linked to from the following overview topics: Differences between the Maya .NET API and the Maya C++ API, Example C++ plug-in descriptions.

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## Detailed Description

Dependency node messages.

This class is used to register callbacks for dependency node messages of specific dependency nodes.

There are 4 add callback methods which will add callbacks for the following messages

- Attribute Changed
- Attribute Added or Removed
- Node Dirty
- Name Changed

The first parameter passed to each of the add callback methods is the depenency node that will trigger the callback.

Callbacks that are registered for attribute changed/addedOrRemoved messages will be passed an AttributeMessage value as a parameter. This value indicates the type of attribute message that has occurred. See the AttributeMessage enum for all available messages.

Each method returns an id which is used to remove the callback.

To remove a callback use MMessage::removeCallback. All callbacks that are registered by a plug-in must be removed by that plug-in when it is unloaded. Failure to do so will result in a fatal error.

`#include <MNodeMessage.h>`

Inheritance diagram for MNodeMessage:
[legend]

List of all members.

## Public Types
enum | AttributeMessage { kConnectionMade = 0x01, kConnectionBroken = 0x02, kAttributeEval = 0x04, kAttributeSet = 0x08, kAttributeLocked = 0x10, kAttributeUnlocked = 0x20, kAttributeAdded = 0x40, kAttributeRemoved = 0x80, kAttributeRenamed = 0x100, kAttributeKeyable = 0x200, kAttributeUnkeyable = 0x400, kIncomingDirection = 0x800, kAttributeArrayAdded = 0x1000, kAttributeArrayRemoved = 0x2000, kOtherPlugSet = 0x4000, kLast = 0x8000 }
| The type of attribute changed/addedOrRemoved messages that has occurred. More...
enum | KeyableChangeMsg { kKeyChangeInvalid = 0, kMakeKeyable, kMakeUnkeyable, kKeyChangeLast }
| Allows you to prevent attributes from becoming (un)keyable. More...
typedef void(* | MAttr2PlugFunction )(MNodeMessage::AttributeMessage msg, MPlug &plug, MPlug &otherPlug, void *clientData)
| Pointer to an AttributeMessage callback which takes two plugs.
typedef void(* | MAttrPlugFunction )(MNodeMessage::AttributeMessage msg, MPlug &plug, void *clientData)
| Pointer to an AttributeMessage callback which takes a single plug.
typedef void(* | MKeyableFunction )(MPlug &plug, void *clientData, MNodeMessage::KeyableChangeMsg msg, bool &decision)
| Pointer to a change in keyability callback function.
## Static Public Member Functions
static MCallbackId | addAttributeChangedCallback (MObject &node, MNodeMessage::MAttr2PlugFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| This method registers a callback for attribute changed messages.
static MCallbackId | addAttributeAddedOrRemovedCallback (MObject &node, MNodeMessage::MAttrPlugFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| Registers callbacks for attribute add/removed messages.
static MCallbackId | addNodeDirtyCallback (MObject &node, MMessage::MNodeFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| Registers a callback for node dirty messages.
static MCallbackId | addNodeDirtyPlugCallback (MObject &node, MMessage::MNodePlugFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| Registers a callback for node dirty messages.
static MCallbackId | addNameChangedCallback (MObject &node, MMessage::MNodeStringFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| Registers a callback for name changed messages.
static MCallbackId | addNodeAboutToDeleteCallback (MObject &node, MMessage::MNodeModifierFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| Registers a callback which will get called when a node is about to be deleted.
static MCallbackId | addNodePreRemovalCallback (MObject &node, MMessage::MNodeFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| Registers a callback which will get called before a node is deleted.
static MCallbackId | addNodeDestroyedCallback (MObject &node, MMessage::MBasicFunction func, void *clientData=NULL, MStatus *ReturnStatus=NULL)
| NodeDestroyed callback.
static MCallbackId | addKeyableChangeOverride (MPlug &plug, MNodeMessage::MKeyableFunction func, void *clientData=NULL, MStatus *status=NULL)
| Attribute keyable state change override.
static const char * | className ()
| Returns the name of this class.

## Member Typedef Documentation

typedef void(* MAttr2PlugFunction)(MNodeMessage::AttributeMessage msg, MPlug &plug, MPlug &otherPlug, void *clientData)

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Pointer to an AttributeMessage callback which takes two plugs.

Parameters:

  [in] | msg | Type of message which caused the function to be called.
  [in,out] | plug | First plug. Meaning depends upon the specific message which invoked the callback.
  [in,out] | otherPlug | Second plug. Meaning depends upon the specific message which invoked the callback.
  [in] | clientData | Pointer to user-defined data supplied when the callback was registered.

typedef void(* MAttrPlugFunction)(MNodeMessage::AttributeMessage msg, MPlug &plug, void *clientData)

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Pointer to an AttributeMessage callback which takes a single plug.

Parameters:

  [in] | msg | Type of message which caused the function to be called.
  [in,out] | plug | Meaning depends upon the specific message which invoked the callback.
  [in] | clientData | Pointer to user-defined data supplied when the callback was registered.

typedef void(* MKeyableFunction)(MPlug &plug, void *clientData, MNodeMessage::KeyableChangeMsg msg, bool &decision)

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Pointer to a change in keyability callback function.

Parameters:

  [in,out] | plug | The plug whose keyability is changing.
  [in] | clientData | Pointer to user-defined data supplied when the callback was registered.
  [in] | msg | Specifies how the plug's keyability is changing.
  [out] | decision | Callback sets this true to accept the change, false to reject it.

## Member Enumeration Documentation

enum AttributeMessage

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The type of attribute changed/addedOrRemoved messages that has occurred.

Enumerator:

  kConnectionMade | a connection has been made to an attribute of this node Search for all occurrences
  kConnectionBroken | a connection has been broken for an attribute of this node Search for all occurrences
  kAttributeEval | an attribute of this node has been evaluated Search for all occurrences
  kAttributeSet | an attribute value of this node has been set Search for all occurrences
  kAttributeLocked | an attribute of this node has been locked Search for all occurrences
  kAttributeUnlocked | an attribute of this node has been unlocked Search for all occurrences
  kAttributeAdded | an attribute has been added to this node Search for all occurrences
  kAttributeRemoved | an attribute has been removed from this node Search for all occurrences
  kAttributeRenamed | an attribute of this node has been renamed Search for all occurrences
  kAttributeKeyable | an attribute of this node has been marked keyable Search for all occurrences
  kAttributeUnkeyable | an attribute of this node has been marked unkeyable Search for all occurrences
  kIncomingDirection | the connection was coming into the node Search for all occurrences
  kAttributeArrayAdded | an array attribute has been added to this node Search for all occurrences
  kAttributeArrayRemoved | an array attribute has been removed from this node Search for all occurrences
  kOtherPlugSet | the otherPlug data has been set Search for all occurrences
  kLast | last value of the enum Search for all occurrences

enum KeyableChangeMsg

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Allows you to prevent attributes from becoming (un)keyable.

Enumerator:

  kKeyChangeInvalid | Search for all occurrences
  kMakeKeyable | Search for all occurrences
  kMakeUnkeyable | Search for all occurrences
  kKeyChangeLast | Search for all occurrences

## Member Function Documentation

MCallbackId addAttributeChangedCallback | ( | MObject & | node,
|  | MNodeMessage::MAttr2PlugFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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This method registers a callback for attribute changed messages.

See the AttributeChanged enum for a list of all possible messages that will trigger the callback.

Note: Attribute Changed messages will not be generated while Maya is either in playback or scrubbing modes. If you need to do something during playback or scrubbing you will have to register a callback for the timeChanged message which is the only message message that is sent during those modes.

The callback function will be passed the type of attribute message that has occurred, the plug(s) for the attributes, and any client data that the user wishes to pass in.

Example callback ( prints out a message when a connection is made or broken ) :

        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;
        }

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: msg the kind of attribute change triggering the callback plug the node's plug where the connection changed otherPlug the plug opposite the node's plug where the connection changed clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

Examples:
  cgfxShaderNode.cpp, D3DResourceManager.cpp, and nodeMessageCmd.cpp.

MCallbackId addAttributeAddedOrRemovedCallback | ( | MObject & | node,
|  | MNodeMessage::MAttrPlugFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Registers callbacks for attribute add/removed messages.

This is a more specific version of addAttributeChanged as only attribute added and attribute removed messages will trigger the callback.

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: msg the kind of attribute change triggering the callback plug the node's plug where the connection changed clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

Examples:
  cgfxShaderNode.cpp.

MCallbackId addNodeDirtyCallback | ( | MObject & | node,
|  | MMessage::MNodeFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Registers a callback for node dirty messages.

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: node The node that has become dirty clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

Examples:
  D3DResourceManager.cpp, NodeMonitor.cpp, and ShapeMonitor.cpp.

MCallbackId addNodeDirtyPlugCallback | ( | MObject & | node,
|  | MMessage::MNodePlugFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Registers a callback for node dirty messages.

This callback provides the plug on the node that was dirtied. Only provides dirty information on input plugs.

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: node The node that has become dirty plug The plug on the node that has become dirty clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

MCallbackId addNameChangedCallback | ( | MObject & | node,
|  | MMessage::MNodeStringFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Registers a callback for name changed messages.

Parameters:

  [in] | node | the node. If this is a NULL MObject then the callback applies to all node name changes.
  [in] | func | the callback function, which takes the following parameters: node the node prevName the previous name of the node clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

Examples:
  NodeMonitor.cpp, and ShapeMonitor.cpp.

MCallbackId addNodeAboutToDeleteCallback | ( | MObject & | node,
|  | MMessage::MNodeModifierFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Registers a callback which will get called when a node is about to be deleted.

The callback will be passed the MDGModifer that will be used to delete the node. This modifier can be used to do any DG modifications, such as disconnections, before the node is deleted. These operations are also stored and performed when the deletion operation is undone or redone.

The callback registered with this method will only get called when the deletion operation is first performed. Undos and redos will be handled solely through the MDGModifier which was passed to the callback on the original deletion. If you also wish to receive notification of deletion events when they are redone, you should register an additional callback using addNodePreRemovalCallback().

When a node is deleted Maya automatically breaks all connections to that node. This process takes place after the callback has been called. This means that if you use the passed-in MDGModifier to break any connections to the node you must be sure to call the modifier's doIt() method before returning from the callback. Otherwise Maya will see that the connections still exist and try to delete them again, which can lead to errors.

The example below shows a callback function which takes the connection coming into the node's input attribute and reconnects it to all of the plugs connected to the node's output attribute:

    import maya.OpenMaya as om

    def rewire(node, dgmod, data):
        nodefn = om.MFnDependencyNode(node)
        try:
            # Find the input plug.
            inPlug = nodefn.findPlug('input')

            # Get the incoming connections.
            srcs = om.MPlugArray()
            inPlug.connectedTo(srcs, True, False)

            if srcs.length() > 0:
                srcPlug = srcs[0]

                outPlug = nodefn.findPlug('output')
                dests = om.MPlugArray()
                outPlug.connectedTo(dests, False, True)

                if dests.length() > 0:
                    # Now that we know we have a valid flow-through
                    # connection, disconnect the source from this node.
                    dgmod.disconnect(srcPlug, inPlug)

                    # Disconnect all of destinations from this node.
                    for i in range(dests.length()):
                        dgmod.disconnect(outPlug, dests[i])

                    # Force our disconnections to be done now.
                    dgmod.doIt()

                    # Make a direct connection from the source to each of
                    # the destinations.
                    for i in range(dests.length()):
                        dgmod.connect(srcPlug, dests[i])
        except:
            # This node does not have an 'input' plug, or does not have
            # an 'output' plug, so let's ignore it.
            pass

Note that it uses the passed-in MDGModifier to perform all the disconnections and connections. This ensures that if the deletion is undone or redone then all of the connections will be restored correctly.

After it is done breaking connections, the callback calls the modifier's doIt() method to commit those disconnections. As noted above, this is necessary to ensure that Maya doesn't see the connections and try to break them again later on.

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: node the node that will be deleted modifier DG modifier used to delete the node clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

Examples:
  D3DResourceManager.cpp, and deletedMsgCmd.cpp.

MCallbackId addNodePreRemovalCallback | ( | MObject & | node,
|  | MMessage::MNodeFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Registers a callback which will get called before a node is deleted.

This callback is called before connections on the node are removed. Unlike the aboutToDelete callback, this callback will be invoked whenever the node is deleted, even during a redo.

Pre-removal and aboutToDelete callbacks serve different purposes. If DG changes need to be made when a node is deleted, the aboutToDelete callback should be used to add undoable operations to an MDGModifier to perform these changes. When the desired actions cannot be accomplished using the MDGModifier passed to the aboutToDelete callback, this callback can be used to receive notification of the deletion event, even during redo.

Note that this callback method should not perform any DG operations.

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: node the node that is being deleted clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

Examples:
  deletedMsgCmd.cpp.

MCallbackId addNodeDestroyedCallback | ( | MObject & | node,
|  | MMessage::MBasicFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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NodeDestroyed callback.

Registers a callback which will get called when a node's destructor is called.

Parameters:

  [in] | node | the node to register the callback for
  [in] | func | the callback function, which takes the following parameters: clientData User defined data passed to the callback function
  [in] | clientData | User defined data that will be passed to the callback function
  [out] | ReturnStatus | status code

Returns:
  Identifier used for removing the callback.

Status Codes:
  - MS::kSuccess Operation succeeded
  - MS::kInsufficientMemory No memory available
  - MS::kFailure Error adding callback

MCallbackId addKeyableChangeOverride | ( | MPlug & | plug,
|  | MNodeMessage::MKeyableFunction | func,
|  | void * | clientData = `NULL`,
|  | MStatus * | ReturnStatus = `NULL`
| ) |  | `[static]`

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Attribute keyable state change override.

This method registers a callback that is invoked by any class that changes the keyable state of an attribute.

When the callback is invoked, the API programmer can make a decision on how to handle the given keyable change event. The programmer can either accept the the keyable state change by returning a decision == 'true' or reject it by returning decision == 'false'.

Note: you can only attach one callback keyable change override callback per attribute. It is an error to attach more than one callback to the same attribute.

Parameters:

  [in] | plug | The plug to which to attach the callback.
  [in] | func | the callback function, which takes the following parameters: plug - The plug that triggered the callback. clientData - User defined data passed to the callback function. eventType - Description of the event. decision - Return true to accept the keyable state change or false to reject it.
  [in] | clientData | User defined data passed back to the user.
  [in] | ReturnStatus | status code

Status Codes:
  - MS::kFailure - Error registering callback. This can occur when a global watcher is already attached to the node.
  - MS::kInsufficientMemory - Not enough memory to register the callback.
  - MS::kInvalidParameter - The given node is not a valid node to register the callback on.
  - MS::kSuccess - Callback successfully added.

const char * className | ( |  | ) | `[static]`

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Returns the name of this class.

Returns:
  The name of this class.

Reimplemented from MMessage.

MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage
MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage MNodeMessage