NAME
SoGroup -
The SoGroup class is a node which managed other node instances.
The internal scene data structures in Coin are managed as directed
graphs. The graphs are built by setting up a hierarchy through the use
of group nodes (either of this type, or from subclasses like
SoSeparator) which is then traversed when applying actions (like
SoGLRenderAction) to it.
SYNOPSIS
#include <Inventor/nodes/SoGroup.h>
Inherits SoNode.
Inherited by SoArray, SoLevelOfDetail, SoLOD, SoMultipleCopy,
SoPathSwitch, SoSeparator, SoSwitch, SoTransformSeparator, SoVRMLLOD,
SoVRMLParent, and SoVRMLSwitch.
Public Member Functions
SoGroup (void)
SoGroup (int nchildren)
virtual void addChild (SoNode *node)
virtual void insertChild (SoNode *child, int newchildindex)
virtual SoNode * getChild (int index) const
virtual int findChild (const SoNode *node) const
virtual int getNumChildren (void) const
virtual void removeChild (int childindex)
virtual void removeChild (SoNode *child)
virtual void removeAllChildren (void)
virtual void replaceChild (int index, SoNode *newchild)
virtual void replaceChild (SoNode *oldchild, SoNode *newchild)
virtual void doAction (SoAction *action)
virtual void GLRender (SoGLRenderAction *action)
virtual void callback (SoCallbackAction *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)
virtual void audioRender (SoAudioRenderAction *action)
virtual SoChildList * getChildren (void) const
Static Public Member Functions
static void initClass (void)
Protected Member Functions
virtual ~SoGroup ()
virtual SbBool readInstance (SoInput *in, unsigned short flags)
virtual SbBool readChildren (SoInput *in)
virtual void copyContents (const SoFieldContainer *from, SbBool
copyconnections)
Protected Attributes
SoChildList * children
Detailed Description
The SoGroup class is a node which managed other node instances.
The internal scene data structures in Coin are managed as directed
graphs. The graphs are built by setting up a hierarchy through the use
of group nodes (either of this type, or from subclasses like
SoSeparator) which is then traversed when applying actions (like
SoGLRenderAction) to it.
SoGroup, SoSeparator, and other classes derived from SoGroup, are the
’tools’ the application programmer uses when making the layout of the
scene graph.
An often asked question about SoGroup nodes is: ’Why is there no
SoGroup::getParent() method?’ The answer to this is that nodes in the
scene graph can have multiple parents, so a simple getParent() method
wouldn’t work. If you have a node pointer (or other node
identification) of a node that you want to remove from the scene graph,
what you need to do is to use an SoSearchAction to find all paths down
to the node, and then invoke SoGroup::removeChild() from all found
parents of the node.
The function would look something like this:
void getParents(SoNode * node, SoNode * root, SoPathList & parents)
{
SoSearchAction sa;
sa.setNode(node);
sa.setInterest(SoSearchAction::ALL);
sa.apply(root);
parents = sa.getPaths();
}
Or if you know that your node of interest has only a single parent:
SoGroup * getParent(SoNode * node, SoNode * root)
{
SoSearchAction sa;
sa.setNode(node);
sa.setInterest(SoSearchAction::FIRST);
sa.apply(root);
SoPath * p = sa.getPath();
assert(p && ’not found’);
if (p->getLength() < 2) { return NULL; } // no parent
return (SoGroup *)p->getNodeFromTail(1);
}
An important note about a potential problem using SoGroup nodes which
it is not common to stumble on, but which makes hard to find bugs when
one does: you should not change the scene graph layout during any
action traversal, as that is not allowed by the internal Coin code.
I.e. do not use addChild(), removeChild(), insertChild() or
replaceChild() from any callback that is triggered directly or
indirectly from an action traversal. The most common way of getting hit
by this error, would be something like the following (simplified)
example:
#include <Inventor/Qt/SoQt.h>
#include <Inventor/Qt/viewers/SoQtExaminerViewer.h>
#include <Inventor/nodes/SoEventCallback.h>
#include <Inventor/nodes/SoSeparator.h>
#include <Inventor/nodes/SoCone.h>
#include <Inventor/manips/SoPointLightManip.h>
#include <Inventor/events/SoMouseButtonEvent.h>
SoPointLightManip * global_pointlightmanip;
SoSeparator * global_root;
// Remove pointlight when clicking right mouse button.
static void
mySelectionC(void * ud, SoEventCallback * n)
{
const SoMouseButtonEvent * mbe = (SoMouseButtonEvent*) n->getEvent();
if ((mbe->getButton() == SoMouseButtonEvent::BUTTON2) &&
(mbe->getState() == SoButtonEvent::DOWN)) {
if (global_pointlightmanip) {
global_root->removeChild(global_pointlightmanip);
global_pointlightmanip = NULL;
}
}
}
int
main(int argc, char ** argv)
{
QWidget * window = SoQt::init(argv[0]);
global_root = new SoSeparator;
global_root->ref();
SoEventCallback * ecb = new SoEventCallback;
ecb->addEventCallback(SoMouseButtonEvent::getClassTypeId(), mySelectionC, 0);
global_root->addChild(ecb);
global_root->addChild(new SoCone);
global_pointlightmanip = new SoPointLightManip;
global_root->addChild(global_pointlightmanip);
SoQtExaminerViewer * viewer = new SoQtExaminerViewer(window);
viewer->setSceneGraph(global_root);
viewer->show();
SoQt::show(window);
SoQt::mainLoop();
global_root->unref();
delete viewer;
return 0;
}
What happens in the above case is this: when clicking with the right
mouse button, the SoQtExaminerViewer converts the Qt event to a Coin
event, which is sent down the scene graph with an SoHandleEventAction.
The action traversal reaches the ’global_root’ SoSeparator node, where
it sees that it should further traverse 3 child nodes (first the
SoEventCallback, then the SoCone, then the SoPointLightManip). When it
then traverses the SoEventCallback, the mySelectionC() callback will be
invoked, which removes the last child. But the SoHandleEventAction will
still continue it’s traversal as if the global_root node has 3 children
-- and the code will crash.
(This exact example would perhaps be straight-forward to handle
internally in Coin, but there are other ways to change the scene graph
layout that are very difficult to handle properly. So in general,
changing layout during action traversal is not allowed.)
What to do in these cases is to change the code inside the callback to
not do any operations that immediately changes the layout of the scene
graph, but to delay it for after the traversal is done. This can e.g.
be done by using a Coin sensor.
FILE FORMAT/DEFAULTS:
Group {
}
Constructor & Destructor Documentation
SoGroup::SoGroup (void) Default constructor.
SoGroup::SoGroup (int nchildren) Constructor.
The argument should be the approximate number of children which is
expected to be inserted below this node. The number need not be exact,
as it is only used as a hint for better memory resource allocation.
SoGroup::~SoGroup () [protected, virtual] Destructor.
Member Function Documentation
void SoGroup::initClass (void) [static] Sets up initialization for data
common to all instances of this class, like submitting necessary
information to the Coin type system.
Reimplemented from SoNode.
Reimplemented in SoVRMLAnchor, SoVRMLBillboard, SoVRMLCollision,
SoVRMLGroup, SoVRMLLOD, SoVRMLParent, SoVRMLSwitch, SoVRMLTransform,
SoShadowGroup, SoAnnotation, SoArray, SoBlinker, SoExtSelection,
SoGeoSeparator, SoLOD, SoLevelOfDetail, SoLocateHighlight,
SoMultipleCopy, SoPathSwitch, SoSelection, SoSeparator, SoSwitch,
SoTransformSeparator, and SoWWWAnchor.
void SoGroup::addChild (SoNode * node) [virtual] Append a child node to the
list of children nodes this group node is managing.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::insertChild (SoNode * child, int newchildindex) [virtual]
Insert a child node at position newchildindex.
newchildindex must be <= this->getNumChildren()
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
SoNode * SoGroup::getChild (int index) const [virtual] Returns pointer to
child node at index.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
int SoGroup::findChild (const SoNode * node) const [virtual] Returns index
in our list of children for child node, or -1 if node is not a child of
this group node.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
int SoGroup::getNumChildren (void) const [virtual] Returns number of child
nodes managed by this group.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::removeChild (int childindex) [virtual] Remove node at
childindex in our list of children.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::removeChild (SoNode * child) [virtual] Remove child from the
set of children managed by this group node. Will decrease the reference
count of child by 1.
This is a convenience method. It will simply call findChild() with
child as argument, and then call removeChild(int) if the child is
found.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::removeAllChildren (void) [virtual] Do not manage the children
anymore. Will dereference all children by 1 as they are removed.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::replaceChild (int index, SoNode * newchild) [virtual] Replace
child at index with newChild.
Dereferences the child previously at index, and increases the reference
count of newChild by 1.
index must be < this->getNumChildren()
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::replaceChild (SoNode * oldchild, SoNode * newchild) [virtual]
Replace oldchild with newchild.
Dereferences oldchild by 1, and increases the reference count of
newchild by 1.
This is a convenience method. It will simply call findChild() with
oldchild as argument, and call replaceChild(int, SoNode*) if the child
is found.
Please note that this method is not virtual in the original SGI
Inventor API.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
void SoGroup::doAction (SoAction * action) [virtual] This function performs
the typical operation of a node for any action.
Reimplemented from SoNode.
Reimplemented in SoVRMLBillboard, SoVRMLGroup, SoVRMLLOD, SoVRMLParent,
SoVRMLSwitch, SoVRMLTransform, SoArray, SoLOD, SoLevelOfDetail,
SoMultipleCopy, SoPathSwitch, SoSeparator, SoSwitch, and
SoTransformSeparator.
void SoGroup::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.
Reimplemented in SoVRMLBillboard, SoVRMLCollision, SoVRMLGroup,
SoVRMLLOD, SoVRMLSwitch, SoAnnotation, SoArray, SoLOD, SoLevelOfDetail,
SoMultipleCopy, SoPathSwitch, SoSeparator, SoSwitch, and
SoTransformSeparator.
void SoGroup::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.
Reimplemented in SoVRMLBillboard, SoVRMLGroup, SoVRMLLOD, SoVRMLSwitch,
SoVRMLTransform, SoArray, SoGeoSeparator, SoLOD, SoLevelOfDetail,
SoMultipleCopy, SoPathSwitch, SoSeparator, SoSwitch, and
SoTransformSeparator.
void SoGroup::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.
Reimplemented in SoVRMLBillboard, SoVRMLGroup, SoVRMLLOD, SoVRMLSwitch,
SoVRMLTransform, SoArray, SoBlinker, SoGeoSeparator, SoLOD,
SoLevelOfDetail, SoMultipleCopy, SoPathSwitch, SoSeparator, SoSwitch,
and SoTransformSeparator.
void SoGroup::getMatrix (SoGetMatrixAction * action) [virtual] Action
method for SoGetMatrixAction.
Updates action by accumulating with the transformation matrix of this
node (if any).
Reimplemented from SoNode.
Reimplemented in SoVRMLBillboard, SoVRMLGroup, SoVRMLSwitch,
SoVRMLTransform, SoArray, SoGeoSeparator, SoMultipleCopy, SoPathSwitch,
SoSeparator, SoSwitch, and SoTransformSeparator.
void SoGroup::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.
Reimplemented in SoVRMLAnchor, SoVRMLSwitch, SoArray, SoExtSelection,
SoLocateHighlight, SoMultipleCopy, SoPathSwitch, SoSelection,
SoSeparator, SoSwitch, and SoWWWAnchor.
void SoGroup::pick (SoPickAction * action) [virtual] Action method for
SoPickAction.
Does common processing for SoPickAction action instances.
Reimplemented from SoNode.
Reimplemented in SoVRMLBillboard, SoVRMLSwitch, SoArray,
SoMultipleCopy, SoPathSwitch, SoSwitch, and SoTransformSeparator.
void SoGroup::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.
Reimplemented in SoVRMLBillboard, SoVRMLGroup, SoVRMLLOD, SoVRMLParent,
SoVRMLSwitch, SoArray, SoMultipleCopy, SoPathSwitch, SoSeparator, and
SoSwitch.
void SoGroup::write (SoWriteAction * action) [virtual] Action method for
SoWriteAction.
Writes out a node object, and any connected nodes, engines etc, if
necessary.
Reimplemented from SoNode.
Reimplemented in SoVRMLGroup, SoVRMLLOD, SoVRMLParent, SoVRMLSwitch,
SoBlinker, and SoSwitch.
void SoGroup::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.
Reimplemented in SoVRMLGroup, SoVRMLLOD, SoVRMLParent, SoVRMLTransform,
SoArray, SoGeoSeparator, SoLOD, SoMultipleCopy, SoPathSwitch,
SoSeparator, SoSwitch, and SoTransformSeparator.
void SoGroup::audioRender (SoAudioRenderAction * action) [virtual] Action
method for SoAudioRenderAction.
Does common processing for SoAudioRenderAction action instances.
Reimplemented from SoNode.
Reimplemented in SoVRMLGroup, SoVRMLLOD, SoVRMLSwitch, SoVRMLTransform,
SoArray, SoLOD, SoLevelOfDetail, SoMultipleCopy, SoPathSwitch,
SoSeparator, SoSwitch, and SoTransformSeparator.
SoChildList * SoGroup::getChildren (void) const [virtual] Returns list of
children.
Reimplemented from SoNode.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
SbBool SoGroup::readInstance (SoInput * in, unsigned short flags)
[protected, virtual] This method is mainly intended for internal use
during file import operations.
It reads a definition of an instance from the input stream in. The
input stream state points to the start of a serialized / persistant
representation of an instance of this class type.
TRUE or FALSE is returned, depending on if the instantiation and
configuration of the new object of this class type went ok or not. The
import process should be robust and handle corrupted input streams by
returning FALSE.
flags is used internally during binary import when reading user
extension nodes, group nodes or engines.
Reimplemented from SoNode.
Reimplemented in SoVRMLLOD, SoVRMLParent, SoVRMLSwitch, and
SoSeparator.
SbBool SoGroup::readChildren (SoInput * in) [protected, virtual] Read all
children of this node from in and attach them below this group in left-
to-right order. Returns FALSE upon read error.
void SoGroup::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.
Reimplemented in SoVRMLLOD, SoVRMLParent, and SoVRMLSwitch.
Member Data Documentation
SoChildList * SoGroup::children [protected] List of managed child nodes.
Reimplemented in SoVRMLParent.
Author
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