vtkDataSet reader again

[John Biddiscombe]

Delving more deeply into vtkDataSetReader it seems that Update() does
correctly stamp the executetime, but

vtkDataSet * vtkDataSetReader::GetOutput() 

calls execute (once) to generate a valid output (and doesn't stamp the output)

then 

void vtkDataSetReader::Update()
{
  if (this->GetOutput())
    {
    this->GetOutput()->Update();
    }
  else
    {
    // execute creates an output
    this->InternalUpdate(NULL);
    }
}

Calls it twice more and this time does successfully stamp the output.

If you yourself call
if (reader->GetOutput()) reader->Update()

you get a bonus execute thrown in!

When your data is 20MB, this translates to a (very) long wait.

One solution would be to use the Outputs[0] array for a check

void vtkDataSetReader::Update()
{
  if (this->Outputs[0])
    {
    this->GetOutput()->Update();
    }
  else
    {
    // execute creates an output
    this->InternalUpdate(NULL);
    }
}

and in GetOutput() instead of doing a full (wasted) execute to simply call

vtkDataSet * vtkDataSetReader::GetOutput() 
{ 
this->Update()
return this->GetOutput();
}

Not sure if this is any good though if you want to just call
GetOutput() and pass the pointer on at program start. 
(Seems my suggestion of a callback on Output set would be useful here -
hint hint)

It looks very messy as it is currently implemented. 

ttfn

John B



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