The Need for Subselection of Devices

Oct 13, 2025 by talynt.org 113 views

Introduction

Gamescope is a powerful tool designed for gaming, preinstalled on SteamOS, and capable of running in a nested mode. While it supports locking mouse and keyboard input to the nested window using command-line options, there is a need for a feature that would allow input to be locked to the nested window while utilizing a subset of available input devices. This feature would be highly beneficial for gaming, enabling split-screen multiplayer for non-Steam games with two sets of peripherals, as well as for Steam games if run under separate accounts.

The Need for Subselection of Devices

Games that are not graphically demanding would not require the full power of the GPU, and for devices such as laptops and handhelds, the ability to support multiseating for both gaming and traditional workloads would be an interesting and valuable feature. The current limitation of Gamescope, where it accepts input and supports locking mouse and keyboard input to the nested window, is not sufficient for the needs of modern gaming.

A Similar Feature in X11

A similar feature previously existed in the X11 project, primarily through Xephyr. While lacking GPU acceleration without additional tools, it allowed for nested multiple sessions. However, this feature was removed about seven years ago in an update to X11's backend input handling, which eliminated the required argument and broke functionality. The removal of this feature was a significant loss for the gaming community, and it is essential to bring it back into the Wayland world.

The Importance of Wayland

Now that the Linux ecosystem has largely transitioned to Wayland, with X11 applications running via XWayland, it seems important to bring this removed feature into the Wayland world. Wayland is a more modern and efficient display server, and it is essential to take advantage of its capabilities to provide a better gaming experience.

Implementation and Potential Challenges

If this feature is added to Gamescope, it may be a useful feature in a future Steam update to allow for local splitscreen on nearly any game; although it may require SteamInput support. The implementation of this feature would require handling devices via libinput, which is a powerful and flexible library for handling input devices. However, it is unclear if direct device handling requires root or not, and this would need to be investigated further.

Conclusion

In conclusion, adding a command-line option for subselection of devices to be used for session input would be a highly beneficial feature for Gamescope. It would enable split-screen multiplayer for non-Steam games with two sets of peripherals, as well as for Steam games if run under separate accounts. The implementation of this feature would require handling devices via libinput, and it may require SteamInput support. However, it is a feature that would be highly valuable for the gaming community, and it is essential to bring it back into the Wayland world.

Potential Roadmap

If this feature is added to Gamescope, the potential roadmap could include:

Investigating the requirements for direct device handling and libinput support
Implementing the feature using libinput and handling devices
Testing the feature to ensure it works as expected
Integrating the feature with SteamInput support
Releasing the feature in a future Steam update

Conclusion

Future Development

If this feature is not added to Gamescope, it may be worth exploring developing it as a separate project. However, this would require significant resources and expertise, and it is unclear if it would be feasible. If this is the case, it would be essential to investigate the requirements for direct device handling and libinput support, and to develop a plan for implementing the feature.

Conclusion

Q: What is the current limitation of Gamescope?

A: The current limitation of Gamescope is that it accepts input and supports locking mouse and keyboard input to the nested window, but it does not allow for the subselection of devices to be used for session input.

Q: Why is this feature important for gaming?

A: This feature is important for gaming because it would enable split-screen multiplayer for non-Steam games with two sets of peripherals, as well as for Steam games if run under separate accounts. It would also allow for the use of devices such as laptops and handhelds for both gaming and traditional workloads.

Q: What is the difference between X11 and Wayland?

A: X11 is an older display server that is still used by many applications, but it has some limitations. Wayland is a more modern and efficient display server that is designed to replace X11. It provides a more secure and flexible way of handling graphics and input.

Q: Why was the similar feature in X11 removed?

A: The similar feature in X11 was removed because it was not compatible with the new backend input handling in X11. This change eliminated the required argument and broke the functionality of the feature.

Q: How would this feature be implemented in Gamescope?

A: This feature would be implemented in Gamescope using libinput, which is a powerful and flexible library for handling input devices. It would require handling devices via libinput and may require SteamInput support.

Q: What are the potential challenges of implementing this feature?

A: The potential challenges of implementing this feature include investigating the requirements for direct device handling and libinput support, implementing the feature using libinput and handling devices, and testing the feature to ensure it works as expected.

Q: What is the potential roadmap for implementing this feature?

A: The potential roadmap for implementing this feature could include investigating the requirements for direct device handling and libinput support, implementing the feature using libinput and handling devices, testing the feature to ensure it works as expected, integrating the feature with SteamInput support, and releasing the feature in a future Steam update.

Q: What are the benefits of implementing this feature?

A: The benefits of implementing this feature include enabling split-screen multiplayer for non-Steam games with two sets of peripherals, as well as for Steam games if run under separate accounts. It would also allow for the use of devices such as laptops and handhelds for both gaming and traditional workloads.

Q: What are the potential risks of implementing this feature?

A: The potential risks of implementing this feature include the complexity of implementing the feature using libinput and handling devices, the potential for bugs and errors, and the need for significant testing and validation to ensure the feature works as expected.

Q: What is the next step in implementing this feature?

A: The next step in implementing this feature would be to investigate the requirements for direct device handling and libinput support, and to develop a plan for implementing the feature.

Q: Who would be responsible for implementing this feature?

A: The responsibility for implementing this feature would likely fall on the Gamescope development team, who would need to work with the libinput team and other stakeholders to ensure the feature is implemented correctly and meets the needs of the gaming community.

Q: What is the expected timeline for implementing this feature?

A: The expected timeline for implementing this feature is unclear, but it would likely take several months to a year or more to implement the feature correctly and ensure it meets the needs of the gaming community.