Input Method Cannot Be Activated in Packaged Slicer on Ubuntu

Support
1

We encountered an input method issue during custom development based on 3D Slicer 5.6.2.

  • Operating System: Ubuntu 22.04.4 LTS

  • Slicer Version: 5.6.2 (custom build)

Problem Description:

  • When running Slicer directly from the build environment (compiled from source), the system input method (e.g., ibus, fcitx) works correctly in text fields.

  • However, when running Slicer from the packaged version (generated using cpack), it becomes impossible to activate the system input method in any text input field.

  • This issue only occurs on Ubuntu. On Windows 11, the packaged Slicer can activate and use the input method without any problems.

Initial Thoughts:

This might be caused by:

  • Missing Qt platform input context plugins in the packaged environment (e.g., libqt5gui5-plugins, qtvirtualkeyboard, or platforminputcontexts).

  • Environment variables such as QT_IM_MODULE, QT_PLUGIN_PATH, or others not being set correctly in the packaged runtime.

  • Differences in runtime plugin loading between build and installed environments.

We’d appreciate any guidance or suggestions from the Slicer developer community on how to resolve this issue.

Is there a recommended way to ensure that input method support (e.g., ibus) is preserved in the packaged Slicer on Linux?

Thanks in advance!

2

Thanks for reporting this. Since you already have a way to reproduce this problem, the best would be if you could investigage this a bit further. First of all, test how Slicer behaves when you build it but not run it from the build tree, but create a package and use that. If your packaged/installed Slicer has the same issues with system input method switches then you can test all your theories (missing Qt plugins is the most likely).