two views with vtkCameraOrientationWidget produces error in second view

[jspanchu]

Description

Set up two independent vtklocal.LocalView instances, each backed by its own
render window/renderer and its own vtkCameraOrientationWidget. Each widget is
registered with its view via LocalView.register_vtk_object so the widget is
serialized into the wasm scene separately from the render window.

Where does the issue originate?

This project (trame-vtklocal), or upstream in VTK.

Version Information

trame-vtklocal - v0.17.1
VTK - 9.6.20260517.dev0

Steps to Reproduce

1. Run this code snippet.

"""Minimal reproducer for the two-view camera-orientation-widget issue.

Sets up two independent ``vtklocal.LocalView`` instances, each backed by its own
render window/renderer and its own ``vtkCameraOrientationWidget``. Each widget is
registered with its view via ``LocalView.register_vtk_object`` so the widget is
serialized into the wasm scene separately from the render window.

Run:
    python issue_orientation_widget.py

Then open the printed URL. The second view's widget update is expected to fail
with client-side errors -- this script exists to reproduce that in isolation.
"""

import os

import vtkmodules.vtkInteractionStyle  # noqa: F401
import vtkmodules.vtkRenderingOpenGL2  # noqa: F401
from trame.app import get_server
from trame.ui.vuetify3 import SinglePageLayout
from trame.widgets import vtklocal, vuetify3
from vtkmodules.vtkFiltersSources import vtkConeSource
from vtkmodules.vtkInteractionWidgets import vtkCameraOrientationWidget
from vtkmodules.vtkRenderingCore import (
    vtkActor,
    vtkPolyDataMapper,
    vtkRenderer,
    vtkRenderWindow,
    vtkRenderWindowInteractor,
)

os.environ.setdefault("VTK_DEFAULT_OPENGL_WINDOW", "vtkEGLRenderWindow")

def setup_vtk_pipeline():
    """Build a render window with a single cone actor and an orientation widget."""
    window = vtkRenderWindow(interactor=vtkRenderWindowInteractor())
    window.interactor.interactor_style.SetCurrentStyleToTrackballCamera()
    renderer = vtkRenderer(background=(0.2, 0.2, 0.2))
    window.AddRenderer(renderer)

    cone = vtkConeSource()
    mapper = vtkPolyDataMapper()
    mapper.SetInputConnection(cone.GetOutputPort())
    actor = vtkActor()
    actor.SetMapper(mapper)
    renderer.AddActor(actor)
    renderer.ResetCamera()

    # Camera orientation widget (axes gizmo) anchored to the renderer.
    orientation_widget = vtkCameraOrientationWidget()
    orientation_widget.parent_renderer = renderer
    orientation_widget.SetInteractor(window.interactor)
    orientation_widget.On()

    return window, renderer, orientation_widget


def main():
    server = get_server(client_type="vue3")

    win_a, _ren_a, widget_a = setup_vtk_pipeline()
    win_b, _ren_b, widget_b = setup_vtk_pipeline()

    with SinglePageLayout(server) as layout:
        layout.title.set_text("Two-view orientation widget reproducer")
        with layout.content, vuetify3.VContainer(
            fluid=True, classes="fill-height pa-0", style="gap: 0;"
        ), vuetify3.VRow(classes="fill-height ma-0"):
            with vuetify3.VCol(cols=6, classes="pa-0"):
                view_a = vtklocal.LocalView(
                    win_a, style="width: 100%; height: 100%;"
                )
                # Register the widget separately from the render window.
                view_a.register_vtk_object(widget_a)
            with vuetify3.VCol(cols=6, classes="pa-0"):
                view_b = vtklocal.LocalView(
                    win_b, style="width: 100%; height: 100%;"
                )
                view_b.register_vtk_object(widget_b)

    server.start()


if __name__ == "__main__":
    main()

2. Second view is blank

Relevant Log Output

JS Error => 2026-06-18 14:12:52.673 (   0.246s) [          8D8374]  vtkAbstractWidget.cxx:106    ERR| vtkCameraOrientationWidget (0xce0b70): The interactor must be set prior to enabling the widget
 JS Error => 2026-06-18 14:12:52.675 (   0.247s) [          8D8374]  vtkAbstractWidget.cxx:106    ERR| vtkCameraOrientationWidget (0xce0b70): The interactor must be set prior to enabling the widget
 JS Error => 2026-06-18 14:12:52.687 (   0.260s) [          8D8374]   vtkObjectManager.cxx:895    ERR| vtkObjectManager (0x925cb0): Cannot update state for object at id=102 because there is no such object!
 JS Error => 2026-06-18 14:12:52.688 (   0.260s) [          8D8374]   vtkObjectManager.cxx:895    ERR| vtkObjectManager (0x925cb0): Cannot update state for object at id=129 because there is no such object!

[jspanchu]

fyi @jourdain