# Trame + WASM: bind custom widget
**URL:** https://discourse.vtk.org/t/trame-wasm-bind-custom-widget/16350
**Category:** Web
**Tags:** trame, vtkwasm, python
**Created:** [March 22, 2026, 8:49pm UTC](https://discourse.vtk.org/t/trame-wasm-bind-custom-widget/16350 "2026-03-22T20:49:21Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@kerim](https://discourse.vtk.org/u/kerim)
#### Post date: [March 22, 2026, 8:49pm UTC](https://discourse.vtk.org/t/trame-wasm-bind-custom-widget/16350/1 "2026-03-22T20:49:21Z")
Hi,
I wrote custom widget in C++ fork of VTK 9.6 and now I’m trying to port it to Trame local view using WASM approach.
My approach is to build VTK WASM, install trame-vtklocal package with VTK\_WASM\_DIR\_OVERRIDE env var set to wasm dir and rutn the trame app. When launching Trame app I get an error:
`JS Error => WASM update failed`
`JS Error => 2026-03-22 23:44:25.998 ( 0.181s) [7E3834]vtkWebAssemblyOpenGLRen:221 ERR| vtkWebAssemblyOpenGLRenderWindow (0x86b098): Error (0) initializing WebGL2.`
`JS Error => 2026-03-22 23:44:25.999 ( 0.182s) [7E3834]vtkWebAssemblyOpenGLRen:245 ERR| vtkWebAssemblyOpenGLRenderWindow (0x86b098): Failed to create Emscripten opengl context`
`JS Error => TypeError: Cannot read properties of undefined (reading ‘getParameter’)`
and the app doesn’t work even though it works when running remote view.
What am I missing?
To configure wasm I use this command:
```auto
emcmake cmake `
-S $env:VTK_SOURCE_DIR `
-B $env:VTK_BUILD_DIR `
-G “Ninja” `
-DCMAKE_BUILD_TYPE=Release `
-DBUILD_SHARED_LIBS=OFF `
-DVTK_GROUP_ENABLE_Web=WANT `
-DVTK_WRAP_SERIALIZATION=ON `
-DVTK_WEBASSEMBLY_THREADS=ON `
-DVTK_WRAP_JAVASCRIPT=OFF `
-DVTK_ENABLE_WEBGPU=ON
```
and I intensionally disable javascript wrapping ( -DVTK\_WRAP\_JAVASCRIPT=OFF) because otherwise it produce the error:
```auto
CMake Error at CMake/vtkModuleWrapJavaScript.cmake:468 (target_link_libraries):
Target “VTK::WebAssemblyAsync” of type EXECUTABLE may not be linked into
another target. One may link only to INTERFACE, OBJECT, STATIC or SHARED
libraries, or to executables with the ENABLE_EXPORTS property set.
Call Stack (most recent call first):
CMakeLists.txt:797 (vtk_module_wrap_javascript)
CMake Error at CMake/vtkModuleWrapJavaScript.cmake:468 (target_link_libraries):
Target “VTK::WebAssembly” of type EXECUTABLE may not be linked into another
target. One may link only to INTERFACE, OBJECT, STATIC or SHARED
libraries, or to executables with the ENABLE_EXPORTS property set.
Call Stack (most recent call first):
CMakeLists.txt:797 (vtk_module_wrap_javascript)
– Configuring incomplete, errors occurred!
```
Appreciate any help
---
### Author:  [@jaswantp](https://discourse.vtk.org/u/jaswantp)
#### Post date: [March 22, 2026, 10:03pm UTC](https://discourse.vtk.org/t/trame-wasm-bind-custom-widget/16350/2 "2026-03-22T22:03:55Z")
Can you show your `