[Paraview] vtkSMProxy: GetSubProxy is protected, but I need it outside the class

[Jérôme]

Thanks for your precisions.

Well you are right! ParaView's proxy mechanism is robust and giving too much
freedom to developers could be really dangerous!
And effectively, my first try to have access to VolumeMapper BlendMode
property was to change the rendering.xml resource in order to expose it.

What I did was:

- adding a IntVectorProperty in FixedPointVolumeRayCastMapper SourceProxy
      <IntVectorProperty
        name="BlendMode"
        command="SetBlendMode"
        default_values="0"
        number_of_elements="1"
        animateable="0">
        <EnumerationDomain name="enum">
          <Entry value="0" text="Composite"/>
          <Entry value="1" text="MaximumIntensity"/>
          <Entry value="2" text="MinimumIntensity"/>
        </EnumerationDomain>
      </IntVectorProperty>

- adding BlendMode as exposed property to
UniformGridVolumeRepresentationProxy in FixedPoint(...) SubProxy
          <Property name="BlendMode"/>

- adding BlendMode as exposed property to UniformGridRepresentation
PVRepresentationProxy in UniformGrid(...) SubProxy.

I changed blend mode by using GetProperty("BlendMode") on the representation
proxy, and it works as well. But in both case (bad unprotected way and
exposing propoerty way), I have to change something in ParaView's tree and
recompile it. It makes my plugin working on my computer only...

Is this BlendMode exposure interesting you and do you want me to send a diff
file of my local 'rendering.xml'?

Thanks again!

Best regards,
Jerome



2009/10/19 Berk Geveci <berk.geveci at kitware.com>

> > - Is there a reason (software design, maybe?) to protect the functions
> that
> > give access to subproxies, whereas the access to properties are
> > -fortunately- public?
> > - Is there another way to access SubProxy without modifying ParaView's
> > sources?
>
> Yes, there is a reason for not exposing the sub-proxies. We wanted the
> access to the sub-proxies to be only through exposed properties
> because we want all proxies (whether they have sub-proxies or not) to
> behave exactly the same way. Allowing access to the sub-proxies makes
> it almost impossible to make sure that developers don't shoot
> themselves in the foot by changing properties of the sub-proxies that
> are supposed to be controlled by the super-proxy. For example, a
> property in the super-proxy may end up setting multiple properties in
> the sub-proxy.
>
> Isn't there another way of doing this? Maybe expose the property you
> are setting? Something like VolumeMapperBlendMode?
>
> -berk
>
> On Mon, Oct 19, 2009 at 2:50 AM, Jérôme <jerome.velut at gmail.com> wrote:
> > Hi,
> >
> > I wrote a plugin that enable a toggle between different BlendMode of the
> > FixedPointVolumeRayCastMapper that is used by ParaView for volume
> rendering.
> > It catches a key event on a render window ('B' pressed) and toggle
> > BlendMode: Composite -> MaximumIntensity -> MinimumIntensity ->
> > Composite->...
> >
> > Here is my way:
> > - When button 'B' pressed:
> >    - get view manager from core instance
> >    - get active view from view manager
> >    - for each representation 'rep' of active view:
> >       - check if 'rep' has a VolumeRepresentation SubProxy
> >       - if yes:
> >          - check if VolumeRepresentation has a
> VolumeFixedPointRayCastMapper
> > SubProxy
> >          - if yes:
> >             - get the vtkFixedPointVolumeRayCastMapper ('mapper') from
> this
> > latter SubProxy
> >             - mapper->SetBlendMode( (++mapper->GetBlendMode(  ))%3 );
> >             - Update and render.
> >
> >
> > For this to work, I need to call vtkSMProxy::GetSubProxy( char* ) from my
> > plugin class. But unfortunately, these functions are protected member. I
> > modified the ParaView sources to make it public, and it work just...
> fine.
> > My questions are:
> > - Is there a reason (software design, maybe?) to protect the functions
> that
> > give access to subproxies, whereas the access to properties are
> > -fortunately- public?
> > - Is there another way to access SubProxy without modifying ParaView's
> > sources?
> >
> > Thanks!
> >
> > Jerome
> >
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