My I3-Emacs Integration

A developer has successfully modified the i3 window manager to route specific key events directly to Emacs when it is the focused window, enabling more integrated control and keybinding sharing between the two programs.

The developer identified that i3 intercepts key events globally via xcb, which prevents passing certain keypresses directly to Emacs. To address this, they added a new feature to i3 that checks the class of the focused window. If the window is Emacs, the key event is forwarded directly to it, bypassing i3’s usual handling.

This was achieved by modifying the Binding structure in i3’s source code to include a ‘passthrough’ class string, which when set, signals that key events should be routed directly to the application. The developer also patched the event handling code to send the key event directly via xcb_send_event().

Why It Matters

This development matters because it offers a way to unify keyboard controls between the window manager and Emacs, reducing latency and improving workflow for users who rely heavily on Emacs for both editing and window management tasks. It also demonstrates how open-source customization can extend the functionality of existing tools.

However, the implementation is still experimental. It does not yet fully address issues like focus loss after forwarding events, and the approach requires manual patching of the i3 source code, which is not suitable for all users.

Background

Previous efforts to integrate Emacs with window managers involved external scripts using tools like xdotool, which introduced latency and lag. The developer’s approach differs by modifying i3 itself to handle key routing more efficiently. The patch builds on prior requests within the i3 community for more flexible keybinding handling but remains a custom, unofficial modification.

“I patched i3 to check the window class and route key events directly to Emacs when focused, bypassing the global key handling.”

— the developer

“This approach could significantly improve workflow for Emacs users, though it’s still in experimental stages.”

— a fellow developer familiar with i3

What Remains Unclear

It remains unclear whether this patch will be adopted into the official i3 codebase or if further refinements are needed to address issues like focus management and event propagation. The long-term stability and compatibility with future i3 versions are also unconfirmed.

What’s Next

The developer plans to continue refining the patch, potentially submitting it for review to the i3 project or sharing it with the community for broader testing. Next steps include addressing focus loss issues and improving the robustness of key event forwarding.

Key Questions

Can I use this patch now?

Currently, the patch is not part of an official release. It requires manual modification of the i3 source code and compilation. Users interested in testing should review the developer’s patch files and instructions, which are available externally.

Will this be integrated into the official i3 release?

This is uncertain. The developer has not announced plans to submit the patch for official inclusion, and the i3 maintainers have previously indicated that passing key events directly to applications is out of scope.

Does this work with all applications or only Emacs?

The current implementation targets Emacs specifically, based on window class matching. Extending this to other applications would require additional modifications.

Are there any known issues or limitations?

Yes. The patch does not yet handle focus loss properly after forwarding events, and it may interfere with certain keybindings or window behaviors. Further testing is needed to ensure stability.

Source: Hacker News