[vtkusers] Implementing vtkImageAlgorithm::RequestData vs ExecuteDataWithInformation

[Elvis Stansvik]

2016-07-05 9:48 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:

> The ExecuteDataWithInformation function is described as a convenience
> function that image readers can implement instead of RequestData. The
> former is called by the latter as follows:
>
>
> //----------------------------------------------------------------------------
> // This is the superclasses style of Execute method.  Convert it into
> // an imaging style Execute method.
> int vtkImageAlgorithm::RequestData(
>   vtkInformation* request,
>   vtkInformationVector** vtkNotUsed( inputVector ),
>   vtkInformationVector* outputVector)
> {
>   // the default implimentation is to do what the old pipeline did find
> what
>   // output is requesting the data, and pass that into ExecuteData
>
>   // which output port did the request come from
>   int outputPort =
>     request->Get(vtkDemandDrivenPipeline::FROM_OUTPUT_PORT());
>
>   // if output port is negative then that means this filter is calling the
>   // update directly, in that case just assume port 0
>   if (outputPort == -1)
>       {
>       outputPort = 0;
>       }
>
>   // get the data object
>   vtkInformation *outInfo =
>     outputVector->GetInformationObject(outputPort);
>   // call ExecuteData
>   this->SetErrorCode( vtkErrorCode::NoError );
>   if (outInfo)
>     {
>     this->ExecuteDataWithInformation(
> outInfo->Get(vtkDataObject::DATA_OBJECT()),
>                                       outInfo );
>     }
>   else
>     {
>     this->ExecuteData(NULL);
>     }
>   // Check for any error set by downstream filter (IO in most case)
>   if ( this->GetErrorCode() )
>     {
>     return 0;
>     }
>
>   return 1;
> }
>
> So all it does is get the output port from which the request came from,
> request the output information and output data object and pass it along to
> ExecuteDataWithInformation. In my case I only have one output port (port
> 0), so that's what I used when I implemented RequestData.
>
> I'm wondering if I should switch to implementing
> ExecuteDataWithInformation. The last thing it does is check for errors set
> by downstream filters with GetErrorCode(). Is this something I should be
> doing? I can't
>

Sorry I meant "the last thing vtkImageAlgorithm::RequestData does", not
"the last thing it does".

Elvis


> see that any of the other image readers that have chosen to implement
> RequestData are doing this (vtkDEMReader, vtkVolume16Reader, ...).
>
> Thanks for any advice,
> Elvis
>
>
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