Class SoEventCallback

  • All Implemented Interfaces:
    SafeDisposable

    public class SoEventCallback
    extends SoNode
    Node which invokes callbacks for events. SoEventCallback will invoke application supplied callbacks during 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 callback invocation to occur. The application callback is 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 callback in an SoEventCallback node, all the callbacks will be invoked when an event occurs, even if one of the callbacks handles the event. However, if the event is handled (i.e. setHandled is called) by any of the callbacks , no subsequent node in the scene graph will see the event. Generally SoEventCallback nodes should be placed near the beginning of the scene graph, so the 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 SoEventCallback node is traversed, then none of the callbacks will be invoked.

    Remember that when using the Open Inventor viewer classes, 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 callback .

    When invoked, this SoEventCallback node will be passed to the callback . Using this object, you can get the event being handled (getEvent()) and query what geometry is under the cursor (getPickedPoint()). These are convenient wrappers around the corresponding methods in the SoHandleEventAction (which you can get using getAction()).

    Picking:
    When getPickedPoint() is called, the handle event action automatically applies an 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 SoHandleEventAction (getAction()), then calling the getPickedPoint() method. The first time this method is called during a handle event traversal, the handle event action will automatically apply its internal 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, getPickedPoint().getNormal() returns (0,0,0) and 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 SoHandleEventAction.getPickRoot().

    To use GPU picking on compatible shapes, it is mandatory to set the pick radius to 0, see SoHandleEventAction.setPickRadius(float radiusInPixels). Compatible shapes are described in the SoRayPickAction section Picking Algorithms.

    EXAMPLE

    An event callback node that handles key and button events

     SoEventCallback  eventNode = new SoEventCallback();
     eventNode.addEventCallback( SoKeyboardEvent.class   , new KeyEventHandler() );
     eventNode.addEventCallback( SoMouseButtonEvent.class, new BtnEventHandler() );
    Handler for key press events
     class KeyEventHandler extends SoEventCallbackCB {
          @Override
        public void invoke( SoEventCallback node ) {
            // Get the event that triggered the callback
            SoKeyboardEvent evt = (SoKeyboardEvent)node.getEvent();
            if (SoKeyboardEvent.isKeyPressEvent(evt, SoKeyboardEvent.Keys.UP_ARROW)) {
                // Do something, then tell action to stop traversal
                node.setHandled();
            }
            else if (SoKeyboardEvent.isKeyPressEvent(evt, SoKeyboardEvent.Keys.DOWN_ARROW)) {
                // Do something, then tell action to stop traversal
                node.setHandled();
            }
        }
     }
    Handler for mouse button events
     class BtnEventHandler extends SoEventCallbackCB {
        @Override
        public void invoke( SoEventCallback node ) {
            SoMouseButtonEvent evt = (SoMouseButtonEvent)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.full.getTail();
                }
            }
        }
     }

    File format/default:

    EventCallback {

    }

    SoInteraction

    See Also:
    SoSelection, SoHandleEventAction, SoRayPickAction, SoDragger
    • Constructor Detail

      • SoEventCallback

        public SoEventCallback()
        Constructor creates an event callback node with no event interest and a NULL path.
    • Method Detail

      • addEventCallback

        public void addEventCallback​(java.lang.String eventClassName,
                                     SoEventCallbackCB f,
                                     java.lang.Object userData)
        Specifies the callbacks to be invoked for different event types. When invoked, this SoEventCallback node will be passed to the callback. For example, passing "com.openinventor.inventor.events.SoMouseButtonEvent" as eventClassName argument means callbacks will be invoked only when a mouse button is pressed or released. Passing "com.openinventor.inventor.events.SoEvent" for the eventClassName will cause the callback to be invoked for every event which passes through this event callback node.
        Parameters:
        eventClassName - the name of one of the class in the package com.openinventor.inventor.events
      • getEvent

        public SoEvent getEvent()
        Returns the event currently being handled, or NULL if traversal is not taking place. This should be called only from callback .
      • setHandled

        public void setHandled()
        Tells the node the event was handled. The callback is responsible for setting whether the event was handled or not. If there is more than one callback registered with an SoEventCallback node, all of them will be invoked, regardless of whether one has handled the event or not. This should be called only from callback .
      • getPath

        public SoPath getPath()
        Gets the path which must be picked in order for the callbacks to be invoked.
      • getPickedPoint

        public SoPickedPoint getPickedPoint()
        Returns pick information during SoHandleEventAction traversal, or NULL if traversal is not taking place. This should be called only from callback .

        When this method is called, an SoRayPickAction is automatically applied to the scene graph that the SoHandleEventAction is traversing, using the current event. However this is only done once for each SoHandleEventAction traversal and the result is cached for subsequent queries during the current traversal.

        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.

      • getAction

        public SoHandleEventAction getAction()
        Returns the SoHandleEventAction currently traversing this node, or NULL if traversal is not taking place. This should be called only from callback .
      • isHandled

        public boolean isHandled()
        Returns whether the event has been handled. This should be called only from callback .
      • releaseEvents

        public void releaseEvents()
        Tells the event callback node to release the grab of events. Event grabbing is requested using grabEvents().
      • setPath

        public void setPath​(SoPath path)
        Sets the path which must be picked in order for the callbacks to be invoked. If the path is NULL, the callbacks will be invoked for every interesting event, as specified by addEventCallback(), regardless of what is picked. The setPath() method makes its own copy of the passed path.
      • grabEvents

        public void grabEvents()
        Tells the event callback node to grab events. While grabbing, the node will consume all events; however, each callback will only be invoked for events of interest.