[vtkusers] Documentation for event callback return values?

David Gobbi david.gobbi at gmail.com
Wed Jun 15 11:30:02 EDT 2016

On Wed, Jun 15, 2016 at 9:27 AM, David Gobbi <david.gobbi at gmail.com> wrote:

> On Wed, Jun 15, 2016 at 7:51 AM, Elvis Stansvik <
> elvis.stansvik at orexplore.com> wrote:
>> Hi all,
>> I noticed in QVTKRenderWindowInteractor that it returns 1 in the callback
>> it sets up for DestroyTimerEvent:
>>     def DestroyTimer(self, obj, evt):
>>         self._Timer.stop()
>>         return 1
>> So I suspect callbacks for this event are expected to return something.
>> But I can't find any info in the docs on which event callbacks are expected
>> to return something (and what), and which are not. Is this info available
>> somewhere?
> I checked the code for the Execute command in vtkPythonCommand.cxx, and
> the return value for callbacks is ignored.  So I'm not sure why this
> callback returns a value.  Prabhu might remember (he wrote the function),
> but that was way back in 2002.  It was probably a simple mistake due to
> cut-and-paste.
> If anything, a non-negative return value would indicate that the callback
> had aborted, e.g. that the callback did not complete whatever action it was
> meant to perform.  But obviously that's not the intent for this method.

Small typo in the above: I meant non-zero, not non-negative.

 - David
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