OIV.Inventor.Nodes.SoEventCallback will invoke application supplied delegatesduring OIV.Inventor.Actions.SoHandleEventAction traversal. Methods allow the application to specify which Open Inventor events should trigger callbacks, and which path must be picked, if any, for the delegateinvocation to occur. The application delegateis able to get information about the event and the pick detail, and may grab events, release events, and set whether the event was handled.

If you register more than one delegatein an OIV.Inventor.Nodes.SoEventCallback node, all the delegateswill be invoked when an event occurs, even if one of the callbacks handles the event. However, if the event is handled (i.e. SetHandledis called) by any of the delegates, no subsequent node in the scene graph will see the event. Generally OIV.Inventor.Nodes.SoEventCallback nodes should be placed near the beginning of the scene graph, so the OIV.Inventor.Actions.SoHandleEventAction does not need to traverse the rest of the scene graph if the event is handled. Note that events may be handled by other nodes in the scene graph, for example draggers and manipulators. If the event is handled before the OIV.Inventor.Nodes.SoEventCallback node is traversed, then none of the delegateswill be invoked.

Remember that when using the Open Inventor viewer classes, OIV.Inventor.Actions.SoHandleEventAction traversal is only done when the viewer is in "selection" mode (the arrow cursor is displayed). Also note that some methods may only be called from the delegate.

When invoked, this OIV.Inventor.Nodes.SoEventCallback node will be passed to the delegate. Using this object, you can get the event being handled (OIV.Inventor.Nodes.SoEventCallback.GetEvent()) and query what geometry is under the cursor (OIV.Inventor.Nodes.SoEventCallback.GetPickedPoint()). These are convenient wrappers around the corresponding methods in the OIV.Inventor.Actions.SoHandleEventAction (which you can get using OIV.Inventor.Nodes.SoEventCallback.GetAction()).

Picking: When OIV.Inventor.Nodes.SoEventCallback.GetPickedPoint() is called, the handle event action automatically applies an OIV.Inventor.Actions.SoRayPickAction to the scene graph using the cursor position in the event. The handle event action remembers the result in case another node needs pick information during the traversal. Often this is more convenient than creating and applying a pick action explicitly.

But note: The handle event action does not enable computation of normal vectors and texture coordinates in the pick action that it creates internally. If you need the normal vector at the point of intersection of the pick ray, then you must create your own pick action and apply it. In this case you can get the node to apply the pick action to by calling the handle event action's getPickRoot() method.

The application method can conveniently find out what, if any, geometry is under the cursor by querying the OIV.Inventor.Actions.SoHandleEventAction (OIV.Inventor.Nodes.SoEventCallback.GetAction()), then calling the OIV.Inventor.Nodes.SoEventCallback.GetPickedPoint() method. The first time this method is called during a handle event traversal, the handle event action will automatically apply its internal OIV.Inventor.Actions.SoRayPickAction to the scene graph returned by getPickRoot(). The result is stored in case other nodes make the same query during the same traversal. The stored result can be cleared by calling clearApplyResult().

Some, but not all, options can be modified on the internal pick action (see for example setPickRadius()). Note that the internal pick action does not compute texture coordinates or normal vector for the picked point. Thus, OIV.Inventor.Nodes.SoEventCallback.GetPickedPoint().getNormal() returns (0,0,0) and OIV.Inventor.Nodes.SoEventCallback.GetPickedPoint().getTextureCoords() returns (0,0,0,0).

If your application needs to apply the pick action itself, for example to set different options, get the appropriate root node by calling OIV.Inventor.Actions.SoHandleEventAction.GetPickRoot().

EXAMPLE

An event callback node that handles key and button events

SoEventCallback eventNode = new SoEventCallback();
eventNode.AddEventCallback( typeof(SoKeyboardEvent)   , new SoEventCallback.EventCB(keyEventCB) );
eventNode.AddEventCallback( typeof(SoMouseButtonEvent), new SoEventCallback.EventCB(btnEventCB) );
. . .

private void keyEventCB( SoEventCallback node )
{
 SoKeyboardEvent evt = (SoKeyboardEvent)node.GetEvent();
 if (evt.GetKey() == SoKeyboardEvent.Keys.UP_ARROW)
 {
   // Do something, then tell action to stop traversal
   node.SetHandled();
 }
 else if (evt.GetKey() == SoKeyboardEvent.Keys.DOWN_ARROW)
 {
   // Do something, then tell action to stop traversal
   node.SetHandled();
 }
}

private void btnEventCB( SoEventCallback node )
{
   SoEvent evt = node.GetEvent();
   // If button 1 was pressed
   if (SoMouseButtonEvent.IsButtonPressEvent( evt, SoMouseButtonEvent.Buttons.BUTTON1 ))
   {
       // Check if any geometry is under the cursor
       SoHandleEventAction action = node.GetAction();
       SoPickedPoint     pickedPt = action.GetPickedPoint();
       if (pickedPt != null)
       {
           SoPath pickedPath = pickedPt.GetPath();
           SoNode pickedNode = pickedPath.FullPath.GetTail();
       }
   }
}

FILE FORMAT/DEFAULT

EventCallback { }

See Also

Reference

OIV.Inventor.Nodes Namespace

OIV.Inventor.Nodes.SoSelection

OIV.Inventor.Actions.SoHandleEventAction

OIV.Inventor.Actions.SoRayPickAction

OIV.Inventor.Draggers.SoDragger