[vtkusers] vtkWarpVector errors when NULL input is checked

[Charl P. Botha]

Dear list,

The following Python code:
c = vtk.vtkWarpVector()
a = c.GetInput()

yields this error:
ERROR: In /home/cpbotha/DoNotBackup/build/VTK/Filtering/vtkExecutive.cxx,
line 265
vtkStreamingDemandDrivenPipeline (0x830d1e0): Attempt to get executive
for connection index 0 on input port 0 of algorithm
vtkWarpVector(0x81a2920), which has 0 connections.

In the ParaView-2-0-2 branch of the VTK CVS.

c.GetOutput() yields the following:
ERROR: In /home/cpbotha/DoNotBackup/build/VTK/Filtering/vtkExecutive.cxx,
line 652
vtkStreamingDemandDrivenPipeline (0x830d1e0): Algorithm
vtkWarpVector(0x81a2920) returned failure for request: vtkInformation
(0x81bc848)
  Debug: Off
  Modified Time: 51
  Reference Count: 1
  Registered Events: (none)
  ALGORITHM_AFTER_FORWARD: 1
  FORWARD_DIRECTION: 0
  REQUEST_DATA_OBJECT: 1

Is this expected behaviour?  How else can I safely check whether a VTK
object has input connections other than doing a GetInput() and
checking for NULL / None?  Why can't I request a GetOutput() pointer /
binding without causing an error?

Thanks for any information,
Charl

-- 
charl p. botha http://cpbotha.net/ http://visualisation.tudelft.nl/