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vtkGarbageCollector Class Reference

Detect and break reference loops. More...

#include <vtkGarbageCollector.h>

Inheritance diagram for vtkGarbageCollector:
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Collaboration diagram for vtkGarbageCollector:
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Public Types

typedef vtkObject Superclass
 

Public Member Functions

virtual int IsA (const char *type)
 Return 1 if this class is the same type of (or a subclass of) the named class. More...
 
vtkGarbageCollectorNewInstance () const
 
void PrintSelf (ostream &os, vtkIndent indent) override
 Methods invoked by print to print information about the object including superclasses. More...
 
- Public Member Functions inherited from vtkObject
 vtkBaseTypeMacro (vtkObject, vtkObjectBase)
 
virtual void DebugOn ()
 Turn debugging output on. More...
 
virtual void DebugOff ()
 Turn debugging output off. More...
 
bool GetDebug ()
 Get the value of the debug flag. More...
 
void SetDebug (bool debugFlag)
 Set the value of the debug flag. More...
 
virtual void Modified ()
 Update the modification time for this object. More...
 
virtual vtkMTimeType GetMTime ()
 Return this object's modified time. More...
 
void PrintSelf (ostream &os, vtkIndent indent) override
 Methods invoked by print to print information about the object including superclasses. More...
 
void RemoveObserver (unsigned long tag)
 
void RemoveObservers (unsigned long event)
 
void RemoveObservers (const char *event)
 
void RemoveAllObservers ()
 
int HasObserver (unsigned long event)
 
int HasObserver (const char *event)
 
int InvokeEvent (unsigned long event)
 
int InvokeEvent (const char *event)
 
unsigned long AddObserver (unsigned long event, vtkCommand *, float priority=0.0f)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
unsigned long AddObserver (const char *event, vtkCommand *, float priority=0.0f)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
vtkCommandGetCommand (unsigned long tag)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
void RemoveObserver (vtkCommand *)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
void RemoveObservers (unsigned long event, vtkCommand *)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
void RemoveObservers (const char *event, vtkCommand *)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
int HasObserver (unsigned long event, vtkCommand *)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
int HasObserver (const char *event, vtkCommand *)
 Allow people to add/remove/invoke observers (callbacks) to any VTK object. More...
 
template<class U , class T >
unsigned long AddObserver (unsigned long event, U observer, void(T::*callback)(), float priority=0.0f)
 Overloads to AddObserver that allow developers to add class member functions as callbacks for events. More...
 
template<class U , class T >
unsigned long AddObserver (unsigned long event, U observer, void(T::*callback)(vtkObject *, unsigned long, void *), float priority=0.0f)
 Overloads to AddObserver that allow developers to add class member functions as callbacks for events. More...
 
template<class U , class T >
unsigned long AddObserver (unsigned long event, U observer, bool(T::*callback)(vtkObject *, unsigned long, void *), float priority=0.0f)
 Allow user to set the AbortFlagOn() with the return value of the callback method. More...
 
int InvokeEvent (unsigned long event, void *callData)
 This method invokes an event and return whether the event was aborted or not. More...
 
int InvokeEvent (const char *event, void *callData)
 This method invokes an event and return whether the event was aborted or not. More...
 
- Public Member Functions inherited from vtkObjectBase
const char * GetClassName () const
 Return the class name as a string. More...
 
virtual void Delete ()
 Delete a VTK object. More...
 
virtual void FastDelete ()
 Delete a reference to this object. More...
 
void InitializeObjectBase ()
 
void Print (ostream &os)
 Print an object to an ostream. More...
 
virtual void Register (vtkObjectBase *o)
 Increase the reference count (mark as used by another object). More...
 
virtual void UnRegister (vtkObjectBase *o)
 Decrease the reference count (release by another object). More...
 
int GetReferenceCount ()
 Return the current reference count of this object. More...
 
void SetReferenceCount (int)
 Sets the reference count. More...
 
void PrintRevisions (ostream &)
 Legacy. More...
 
virtual void PrintHeader (ostream &os, vtkIndent indent)
 Methods invoked by print to print information about the object including superclasses. More...
 
virtual void PrintTrailer (ostream &os, vtkIndent indent)
 Methods invoked by print to print information about the object including superclasses. More...
 

Static Public Member Functions

static int IsTypeOf (const char *type)
 
static vtkGarbageCollectorSafeDownCast (vtkObjectBase *o)
 
static vtkGarbageCollectorNew ()
 
static void Collect ()
 Collect immediately using any objects whose collection was previously deferred as a root for the reference graph walk. More...
 
static void Collect (vtkObjectBase *root)
 Collect immediately using the given object as the root for a reference graph walk. More...
 
static void DeferredCollectionPush ()
 Push/Pop whether to do deferred collection. More...
 
static void DeferredCollectionPop ()
 Push/Pop whether to do deferred collection. More...
 
static void SetGlobalDebugFlag (bool flag)
 Set/Get global garbage collection debugging flag. More...
 
static bool GetGlobalDebugFlag ()
 Set/Get global garbage collection debugging flag. More...
 
- Static Public Member Functions inherited from vtkObject
static vtkObjectNew ()
 Create an object with Debug turned off, modified time initialized to zero, and reference counting on. More...
 
static void BreakOnError ()
 This method is called when vtkErrorMacro executes. More...
 
static void SetGlobalWarningDisplay (int val)
 This is a global flag that controls whether any debug, warning or error messages are displayed. More...
 
static void GlobalWarningDisplayOn ()
 This is a global flag that controls whether any debug, warning or error messages are displayed. More...
 
static void GlobalWarningDisplayOff ()
 This is a global flag that controls whether any debug, warning or error messages are displayed. More...
 
static int GetGlobalWarningDisplay ()
 This is a global flag that controls whether any debug, warning or error messages are displayed. More...
 
- Static Public Member Functions inherited from vtkObjectBase
static vtkTypeBool IsTypeOf (const char *name)
 Return 1 if this class type is the same type of (or a subclass of) the named class. More...
 
static vtkObjectBaseNew ()
 Create an object with Debug turned off, modified time initialized to zero, and reference counting on. More...
 

Protected Member Functions

virtual vtkObjectBaseNewInstanceInternal () const
 
 vtkGarbageCollector ()
 
 ~vtkGarbageCollector () override
 
- Protected Member Functions inherited from vtkObject
 vtkObject ()
 
 ~vtkObject () override
 
void RegisterInternal (vtkObjectBase *, vtkTypeBool check) override
 
void UnRegisterInternal (vtkObjectBase *, vtkTypeBool check) override
 
void InternalGrabFocus (vtkCommand *mouseEvents, vtkCommand *keypressEvents=nullptr)
 These methods allow a command to exclusively grab all events. More...
 
void InternalReleaseFocus ()
 These methods allow a command to exclusively grab all events. More...
 
- Protected Member Functions inherited from vtkObjectBase
 vtkObjectBase ()
 
virtual ~vtkObjectBase ()
 
virtual void CollectRevisions (ostream &)
 
virtual void ReportReferences (vtkGarbageCollector *)
 
 vtkObjectBase (const vtkObjectBase &)
 
void operator= (const vtkObjectBase &)
 

Friends

class vtkGarbageCollectorManager
 
class vtkObjectBaseToGarbageCollectorFriendship
 
void VTKCOMMONCORE_EXPORT vtkGarbageCollectorReportInternal (vtkGarbageCollector *, vtkObjectBase *, void *, const char *)
 

Additional Inherited Members

- Protected Attributes inherited from vtkObject
bool Debug
 
vtkTimeStamp MTime
 
vtkSubjectHelper * SubjectHelper
 
- Protected Attributes inherited from vtkObjectBase
vtkAtomicInt32 ReferenceCount
 
vtkWeakPointerBase ** WeakPointers
 

Detailed Description

Detect and break reference loops.

vtkGarbageCollector is used by VTK classes that may be involved in reference counting loops (such as Algorithm <-> Executive). It detects strongly connected components of the reference graph that have been leaked deletes them. The garbage collector uses the ReportReferences method to search the reference graph and construct a net reference count for each connected component. If the net reference count is zero the entire set of objects is deleted. Deleting each component may leak other components, which are then collected recursively.

To enable garbage collection for a class, add these members:

public:
void Register(vtkObjectBase* o) override
{
this->RegisterInternal(o, true);
}
void UnRegister(vtkObjectBase* o) override
{
this->UnRegisterInternal(o, true);
}
protected:
void ReportReferences(vtkGarbageCollector* collector) override
{
// Report references held by this object that may be in a loop.
this->Superclass::ReportReferences(collector);
vtkGarbageCollectorReport(collector, this->OtherObject, "Other Object");
}

The implementations should be in the .cxx file in practice. It is important that the reference be reported using the real pointer or smart pointer instance that holds the reference. When collecting the garbage collector will actually set this pointer to nullptr. The destructor of the class should be written to deal with this. It is also expected that an invariant is maintained for any reference that is reported. The variable holding the reference must always either be nullptr or refer to a fully constructed valid object. Therefore code like "this->Object->UnRegister(this)" must be avoided if "this->Object" is a reported reference because it is possible that the object is deleted before UnRegister returns but then "this->Object" will be left as a dangling pointer. Instead use code like

vtkObjectBase* obj = this->Object;
this->Object = 0;
obj->UnRegister(this);

so that the reported reference maintains the invariant.

If subclassing from a class that already supports garbage collection, one need only provide the ReportReferences method.

Tests:
vtkGarbageCollector (Tests)

Definition at line 99 of file vtkGarbageCollector.h.

Member Typedef Documentation

Definition at line 102 of file vtkGarbageCollector.h.

Constructor & Destructor Documentation

vtkGarbageCollector::vtkGarbageCollector ( )
protected
vtkGarbageCollector::~vtkGarbageCollector ( )
overrideprotected

Member Function Documentation

static int vtkGarbageCollector::IsTypeOf ( const char *  type)
static
virtual int vtkGarbageCollector::IsA ( const char *  name)
virtual

Return 1 if this class is the same type of (or a subclass of) the named class.

Returns 0 otherwise. This method works in combination with vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkObjectBase.

static vtkGarbageCollector* vtkGarbageCollector::SafeDownCast ( vtkObjectBase o)
static
virtual vtkObjectBase* vtkGarbageCollector::NewInstanceInternal ( ) const
protectedvirtual
vtkGarbageCollector* vtkGarbageCollector::NewInstance ( ) const
void vtkGarbageCollector::PrintSelf ( ostream &  os,
vtkIndent  indent 
)
overridevirtual

Methods invoked by print to print information about the object including superclasses.

Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from vtkObjectBase.

static vtkGarbageCollector* vtkGarbageCollector::New ( )
static
static void vtkGarbageCollector::Collect ( )
static

Collect immediately using any objects whose collection was previously deferred as a root for the reference graph walk.

Strongly connected components in the reference graph are identified. Those with a net reference count of zero are deleted. When a component is deleted it may remove references to other components that are not part of the same reference loop but are held by objects in the original component. These removed references are handled as any other and their corresponding checks may be deferred. This method keeps collecting until no deferred collection checks remain.

static void vtkGarbageCollector::Collect ( vtkObjectBase root)
static

Collect immediately using the given object as the root for a reference graph walk.

Strongly connected components in the reference graph are identified. Those with a net reference count of zero are deleted. When a component is deleted it may remove references to other components that are not part of the same reference loop but are held by objects in the original component. These removed references are handled as any other and their corresponding checks may be deferred. This method does continue collecting in this case.

static void vtkGarbageCollector::DeferredCollectionPush ( )
static

Push/Pop whether to do deferred collection.

Whenever the total number of pushes exceeds the total number of pops collection will be deferred. Code can call the Collect method directly to force collection.

static void vtkGarbageCollector::DeferredCollectionPop ( )
static

Push/Pop whether to do deferred collection.

Whenever the total number of pushes exceeds the total number of pops collection will be deferred. Code can call the Collect method directly to force collection.

static void vtkGarbageCollector::SetGlobalDebugFlag ( bool  flag)
static

Set/Get global garbage collection debugging flag.

When set to true, all garbage collection checks will produce debugging information.

static bool vtkGarbageCollector::GetGlobalDebugFlag ( )
static

Set/Get global garbage collection debugging flag.

When set to true, all garbage collection checks will produce debugging information.

Friends And Related Function Documentation

friend class vtkGarbageCollectorManager
friend

Definition at line 185 of file vtkGarbageCollector.h.

friend class vtkObjectBaseToGarbageCollectorFriendship
friend

Definition at line 186 of file vtkGarbageCollector.h.

void VTKCOMMONCORE_EXPORT vtkGarbageCollectorReportInternal ( vtkGarbageCollector ,
vtkObjectBase ,
void *  ,
const char *   
)
friend

The documentation for this class was generated from the following file: