[vtk-developers] vtkWidgets passed between Renderers

[Daniel Haehn]

Hi devels,

we encounter a problem when trying to pass a vtkWidget between
different vtkRenderers in a render window in 3D Slicer's lightbox
view.

I wrote the following test to demonstrate:

https://github.com/haehn/VTK/tree/widget-multipleRenderers-Test

I added a test 'TestSeedWidget3.cxx' (bin/WidgetsCxxTests
"TestSeedWidget3" -I) which tries to simulate a minimal scenario with
two renderers and one seedwidget.

The test already has problems displaying the widget when two renderers
with different viewports are configured. This is why line:
56   //ren2->SetViewport(rightViewport);
is commented.

The widget simply does not even appear if line 56 is un-commented.

Do you know why this is happening? And, assuming this can be solved:
do you know why it is not possible to pass vtkWidgets along multiple
renderers? Are we doing something wrong?

Thanks,
Daniel