Slicer3:VTK Observer Debugging - Revision history

Pieper: /* Debugging Observers */

2008-12-05T13:14:23Z

Debugging Observers

Pieper: /* Removing Observers */

2008-12-05T13:13:51Z

Removing Observers

Marianna: 4 revisions

2008-05-15T17:54:02Z

4 revisions

Pieper at 16:36, 30 January 2007

2007-01-30T16:36:55Z

Pieper at 18:44, 27 January 2007

2007-01-27T18:44:29Z

Pieper: /* Debug All */

2007-01-23T19:42:08Z

Debug All

Andy: Update from Wiki

2006-12-18T13:40:17Z

Update from Wiki

New page

This page has some minor changes to VTK that have helped in Slicer3 debugging. It would make sense to improve these techniques and make them conditionally compilable in VTK so people can better understand their code.

It would also be good if there were signatures for AddObserver that allowed additional information to be associated with the particular observer so that introspections of the vtkCommand instances could be more informative. Extra information could include the class name of or a pointer to the 'owner' of the observer and/or a text string comment added by the programmer.

== Removing Observers ==

Below is a modified method for use in Common/vtkObject.cxx that removes observers before calling 'delete' on the instance.

//----------------------------------------------------------------------------
void vtkObject::UnRegisterInternal(vtkObjectBase* o, int check)
{
// Print debugging messages.
if(o)
{
vtkDebugMacro(<< "UnRegistered by "
<< o->GetClassName() << " (" << o << "), ReferenceCount = "
<< (this->ReferenceCount-1));
}
else
{
vtkDebugMacro(<< "UnRegistered by NULL, ReferenceCount = "
<< (this->ReferenceCount-1));
}

if(this->ReferenceCount == 1)
{
// The reference count is 1, so the object is about to be deleted.
// Invoke the delete event.
this->InvokeEvent(vtkCommand::DeleteEvent, 0);

// Make sure we don't invoke any more events during destructor
if ( this->SubjectHelper )
{
vtkObserver *elem = this->SubjectHelper->Start;
vtkObserver *next;
while (elem)
{
next = elem->Next;
delete elem;
elem = next;
}
this->SubjectHelper->Start = NULL;
}
}

// Decrement the reference count.
this->Superclass::UnRegisterInternal(o, check);
}

== Debugging Observers ==

The code below, also in Common/vtkObject.cxx adds debug printouts to help figure out which observers are being invoked in response to events. See [[Slicer3:VTK_Observer_Debugging:ExampleOutput|example output]] for this modification.

int vtkSubjectHelper::InvokeEvent(unsigned long event, void *callData,
vtkObject *self)
{
#define INDENT(__indent) {for (int __ii = 0; __ii < (__indent); __ii++) {cerr << " ";}}

static int indent = 0;
this->ListModified = 0;

vtkObserver *elem = this->Start;
int commandCount = 0;
while (elem)
{
elem->Visited = 0;
elem=elem->Next;
commandCount++;
}

INDENT(indent);
cerr << "{ "<< commandCount << " commands for " << self->GetClassName() << " event is " << vtkCommand::GetStringFromEventId(event) << "\n";
indent++;

commandCount = 0;
elem = this->Start;
vtkObserver *next;
while (elem)
{
// store the next pointer because elem could disappear due to Command
commandCount++;
next = elem->Next;
if (!elem->Visited &&
elem->Event == event || elem->Event == vtkCommand::AnyEvent)
{
elem->Visited = 1;
vtkCommand* command = elem->Command;
command->Register(command);
command->SetAbortFlag(0);

INDENT(indent);
cerr << "{ " << commandCount << " Invoking "<< vtkCommand::GetStringFromEventId(event)
<< " on " << self->GetClassName() << "\n";

elem->Command->Execute(self,event,callData);

INDENT(indent);
cerr << "} " << commandCount << " Returned from "<< vtkCommand::GetStringFromEventId(event)
<< " on " << self->GetClassName() << "\n";

// if the command set the abort flag, then stop firing events
// and return
if(command->GetAbortFlag())
{
command->UnRegister();
indent--;
INDENT(indent);
cerr << "} aborted " << self->GetClassName() << "\n";
return 1;
}
command->UnRegister();
}
else
{
INDENT(indent);
cerr << " -- " << commandCount << " Skipping "<< vtkCommand::GetStringFromEventId(elem->Event) << "\n";
}
if (this->ListModified)
{
elem = this->Start;
this->ListModified = 0;
}
else
{
elem = next;
}
}

indent--;
INDENT(indent);
cerr << "} finished " << self->GetClassName() << "\n";

return 0;
}

== Debug All ==

The following changes to Common/vtkSetGet.h turns on debugging for all objects by default.

<nowiki>Index: Common/vtkSetGet.h
===================================================================
RCS file: /cvsroot/VTK/VTK/Common/vtkSetGet.h,v
retrieving revision 1.128.4.3
diff -r1.128.4.3 vtkSetGet.h
616a617
> ret->DebugOn(); \
619c620,622
< return new thisClass; \
---
> thisClass* retClass = new thisClass; \
> retClass->DebugOn(); \
> return (retClass); \
630c633,635
< return thisClass::New(); \
---
> thisClass* retClass = thisClass::New(); \
> retClass->DebugOn(); \
> return (retClass); \
</nowiki>

@@ Line 138: / Line 138: @@
 == Debug All ==
-The following changes to Common/vtkSetGet.h turns on debugging for all objects by default.  (Lots of output!).
+The following changes to Common/vtkSetGet.h turns on debugging for all objects by default.  (Lots of output!).  I usually redirect the output to a file and then grep for the class name, and then for the string 'egisterd' like
   <nowiki>Index: Common/vtkSetGet.h

← Older revision		Revision as of 18:44, 27 January 2007
Line 2:		Line 2:

	It would also be good if there were signatures for AddObserver that allowed additional information to be associated with the particular observer so that introspections of the vtkCommand instances could be more informative. Extra information could include the class name of or a pointer to the 'owner' of the observer and/or a text string comment added by the programmer.		It would also be good if there were signatures for AddObserver that allowed additional information to be associated with the particular observer so that introspections of the vtkCommand instances could be more informative. Extra information could include the class name of or a pointer to the 'owner' of the observer and/or a text string comment added by the programmer.
		+
		+	See also [[Slicer3:VTK Leak Debugging]]

	== Removing Observers ==		== Removing Observers ==

@@ Line 54: / Line 54: @@
 The code below, also in Common/vtkObject.cxx adds debug printouts to help figure out which observers are being invoked in response to events. See [[Slicer3:VTK_Observer_Debugging:ExampleOutput|example output]] for this modification.
+<pre>
    int vtkSubjectHelper::InvokeEvent(unsigned long event, void *callData,
                                       vtkObject *self)
@@ Line 136: / Line 136: @@
      return 0;
+   }
 == Debug All ==

@@ Line 8: / Line 8: @@
 Below is a modified method for use in Common/vtkObject.cxx that removes observers before calling 'delete' on the instance.
+<pre>
    //----------------------------------------------------------------------------
    void vtkObject::UnRegisterInternal(vtkObjectBase* o, int check)
@@ Line 49: / Line 49: @@
      this->Superclass::UnRegisterInternal(o, check);
+   }
 == Debugging Observers ==

← Older revision	Revision as of 17:54, 15 May 2008
(No difference)