SoCallback(3)

NAME
SoCallback - The SoCallback class is a node type which provides a means of setting callback hooks in the scene graph.

By inserting SoCallback nodes in a scene graph, the application programmer can set up functions to be executed at certain points in the traversal.

SYNOPSIS

#include <Inventor/nodes/SoCallback.h>

Inherits SoNode.

  Public Member Functions
virtual SoType getTypeId (void) const
SoCallback (void)
void setCallback (SoCallbackCB *function, void *userdata=NULL)
virtual void doAction (SoAction *action)
virtual void callback (SoCallbackAction *action)
virtual void GLRender (SoGLRenderAction *action)
virtual void getBoundingBox (SoGetBoundingBoxAction *action)
virtual void getMatrix (SoGetMatrixAction *action)
virtual void handleEvent (SoHandleEventAction *action)
virtual void pick (SoPickAction *action)
virtual void search (SoSearchAction *action)
virtual void write (SoWriteAction *action)
virtual void getPrimitiveCount (SoGetPrimitiveCountAction *action)

  Static Public Member Functions
static SoType getClassTypeId (void)
static void initClass (void)

  Protected Member Functions
virtual const SoFieldData * getFieldData (void) const
virtual ~SoCallback ()
virtual void copyContents (const SoFieldContainer *from, SbBool copyconnections)

  Static Protected Member Functions
static const SoFieldData ** getFieldDataPtr (void)

  Additional Inherited Members

Detailed Description

The SoCallback class is a node type which provides a means of setting callback hooks in the scene graph.

By inserting SoCallback nodes in a scene graph, the application programmer can set up functions to be executed at certain points in the traversal. The callback function will be executed during traversal of any action, so check the type of the action argument of the callback function if you only want to run your code at specific actions.

FILE FORMAT/DEFAULTS:

Callback {
}

Constructor & Destructor Documentation

  SoCallback::SoCallback (void)
Constructor.

  SoCallback::~SoCallback () [protected], [virtual]
Destructor.

Member Function Documentation

  SoType SoCallback::getTypeId (void) const [virtual]
Returns the type identification of an object derived from a class inheriting SoBase. This is used for run-time type checking and 'downward' casting.

Usage example:

void foo(SoNode * node)
{
  if (node->getTypeId() == SoFile::getClassTypeId()) {
    SoFile * filenode = (SoFile *)node;  // safe downward cast, knows the type
  }
}

For application programmers wanting to extend the library with new nodes, engines, nodekits, draggers or others: this method needs to be overridden in all subclasses. This is typically done as part of setting up the full type system for extension classes, which is usually accomplished by using the pre-defined macros available through for instance Inventor/nodes/SoSubNode.h (SO_NODE_INIT_CLASS and SO_NODE_CONSTRUCTOR for node classes), Inventor/engines/SoSubEngine.h (for engine classes) and so on.

For more information on writing Coin extensions, see the class documentation of the toplevel superclasses for the various class groups.

Implements SoBase.

  const SoFieldData * SoCallback::getFieldData (void) const [protected], [virtual]
Returns a pointer to the class-wide field data storage object for this instance. If no fields are present, returns NULL.

Reimplemented from SoFieldContainer.

  void SoCallback::setCallback (SoCallbackCB * function, void * userdata = NULL)
Set up the function to call at traversal of this node. userdata will be passed back as the first argument of the callback function. Setting function to NULL removes the previously set callback function.

If you want a callback only for a specific action, you must (in your callback function) remember to check which action invoked the callback, for instance like this:

void mycallback(void * userdata, SoAction * action)
{
  if (action->isOfType(SoGLRenderAction::getClassTypeId())) {
    // do stuff specific for GL rendering here.
  }
}

Please note that SoCallback nodes under a Separator might be included in a cache. Cached nodes are not traversed, and you'll not receive any callbacks. If you want to make sure that your callback is called every time the scene graph is rendered, you must invalidate the render cache in your callback:

void mycallback(void * userdata, SoAction * action)
{
  if (action->isOfType(SoGLRenderAction::getClassTypeId())) {
    SoCacheElement::invalidate(action->getState());
  }
}

If you want to invalidate all caches (for instance also the bounding box cache), you can do this in your callback:

void mycallback(void * userdata, SoAction * action)
{
  SoState * state = action->getState();
  if (state->isElementEnabled(SoCacheElement::getClassStackIndex())) {
    SoCacheElement::invalidate(state);
  }
}

  void SoCallback::doAction (SoAction * action) [virtual]
This function performs the typical operation of a node for any action.

Reimplemented from SoNode.

  void SoCallback::callback (SoCallbackAction * action) [virtual]
Action method for SoCallbackAction.

Simply updates the state according to how the node behaves for the render action, so the application programmer can use the SoCallbackAction for extracting information about the scene graph.

Reimplemented from SoNode.

  void SoCallback::GLRender (SoGLRenderAction * action) [virtual]
Action method for the SoGLRenderAction.

This is called during rendering traversals. Nodes influencing the rendering state in any way or who wants to throw geometry primitives at OpenGL overrides this method.

Reimplemented from SoNode.

  void SoCallback::getBoundingBox (SoGetBoundingBoxAction * action) [virtual]
Action method for the SoGetBoundingBoxAction.

Calculates bounding box and center coordinates for node and modifies the values of the action to encompass the bounding box for this node and to shift the center point for the scene more towards the one for this node.

Nodes influencing how geometry nodes calculates their bounding box also overrides this method to change the relevant state variables.

Reimplemented from SoNode.

  void SoCallback::getMatrix (SoGetMatrixAction * action) [virtual]
Action method for SoGetMatrixAction.

Updates action by accumulating with the transformation matrix of this node (if any).

Reimplemented from SoNode.

  void SoCallback::handleEvent (SoHandleEventAction * action) [virtual]
Action method for SoHandleEventAction.

Inspects the event data from action, and processes it if it is something which this node should react to.

Nodes influencing relevant state variables for how event handling is done also overrides this method.

Reimplemented from SoNode.

  void SoCallback::pick (SoPickAction * action) [virtual]
Action method for SoPickAction.

Does common processing for SoPickAction action instances.

Reimplemented from SoNode.

  void SoCallback::search (SoSearchAction * action) [virtual]
Action method for SoSearchAction.

Compares the search criteria from the action to see if this node is a match. Searching is done by matching up all criteria set up in the SoSearchAction -- if any of the requested criteria is a miss, the search is not deemed successful for the node.

See also:
    SoSearchAction

Reimplemented from SoNode.

  void SoCallback::write (SoWriteAction * action) [virtual]
Action method for SoWriteAction.

Writes out a node object, and any connected nodes, engines etc, if necessary.

Reimplemented from SoNode.

  void SoCallback::getPrimitiveCount (SoGetPrimitiveCountAction * action) [virtual]
Action method for the SoGetPrimitiveCountAction.

Calculates the number of triangle, line segment and point primitives for the node and adds these to the counters of the action.

Nodes influencing how geometry nodes calculates their primitive count also overrides this method to change the relevant state variables.

Reimplemented from SoNode.

  void SoCallback::copyContents (const SoFieldContainer * from, SbBool copyconnections) [protected], [virtual]
Makes a deep copy of all data of from into this instance, except external scenegraph references if copyconnections is FALSE.

This is the protected method that should be overridden by extension node / engine / dragger / whatever subclasses which needs to account for internal data that are not handled automatically.

For copying nodes from application code, you should not invoke this function directly, but rather call the SoNode::copy() function:

SoNode * mynewnode = templatenode->copy();

The same also goes for engines.

Make sure that when you override the copyContents() method in your extension class that you also make it call upwards to it's parent superclass in the inheritance hierarchy, as copyContents() in for instance SoNode and SoFieldContainer does important work. It should go something like this:

void
MyCoinExtensionNode::copyContents(const SoFieldContainer * from,
                                  SbBool copyconnections)
{
  // let parent superclasses do their thing (copy fields, copy
  // instance name, etc etc)
  SoNode::copyContents(from, copyconnections);
  // [..then copy internal data..]
}

Reimplemented from SoNode.

Author

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