Kitty: Ctrl+J Inputting As Ctrl+Shift+J Via RDP - Bug Fix

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Kitty Terminal: Fixing Ctrl+J Input as Ctrl+Shift+J over RDP

Hey guys! Having trouble with Ctrl+J showing up as Ctrl+Shift+J in Kitty when you're using Remote Desktop Protocol (RDP)? You're not alone! This article dives deep into this quirky bug, offering insights and potential solutions to get your keyboard shortcuts working smoothly again. We'll break down the issue, explore the environment where it occurs, and analyze the debug logs to understand what's happening under the hood.

Understanding the Ctrl+J to Ctrl+Shift+J Bug in Kitty

So, you're trying to use the Ctrl+J shortcut in Kitty, but instead of the expected behavior, you're seeing Ctrl+Shift+J. Frustrating, right? This issue seems to pop up specifically when using Kitty through a Remote Desktop Protocol connection. Let's break down the scenario where this happens:

  • The Setup: You're on a macOS machine, connecting to a remote Linux OS via RDP. This is a pretty common setup for developers and system administrators who need to work on remote servers.
  • The Problem: When you press Ctrl+J within Kitty on the remote Linux machine, the application registers it as Ctrl+Shift+J.
  • The Oddity: The bug is inconsistent! Toggling Caps Lock twice seems to temporarily fix the issue, but it returns after another Caps Lock toggle.

This inconsistent behavior makes it particularly tricky to diagnose. But don't worry, we're going to dig into the details to figure out what's going on.

Why is this happening?

At first glance, this issue seems like a simple keyboard mapping problem. However, the intermittent nature of the bug, specifically its interaction with the Caps Lock key, suggests a deeper issue. Here are some potential causes we'll be exploring:

  • Keyboard Layout Mismatch: The keyboard layout on your local macOS machine might be interfering with the layout on the remote Linux machine.
  • RDP Translation Issues: RDP might be misinterpreting the Ctrl+J keystroke and sending the wrong signal to the remote machine.
  • Kitty's Input Handling: There might be a bug in how Kitty handles keyboard input, especially in conjunction with RDP and Caps Lock.

We'll delve into each of these possibilities as we analyze the debug logs and environment details.

Reproducing the Bug: A Step-by-Step Guide

To effectively troubleshoot this issue, it's crucial to reproduce it consistently. Here's a detailed guide based on the original bug report:

  1. Connect via RDP: Establish an RDP connection from your macOS machine to a remote Linux OS.
  2. Open a Key Test Website: Inside the remote Linux environment, open a website like https://key-test.com. This website is excellent for displaying the exact key combinations your browser receives.
  3. Input Ctrl+J (Initial Incorrect Behavior): Press Ctrl+J. The website should report Ctrl+Shift+J.
  4. Toggle Caps Lock (Temporary Fix): Press the Caps Lock key twice (toggle it on and then off).
  5. Input Ctrl+J (Correct Behavior): Press Ctrl+J again. This time, the website should correctly report Ctrl+J.
  6. Toggle Caps Lock Again (Bug Returns): Press the Caps Lock key twice again.
  7. Input Ctrl+J (Incorrect Behavior Returns): Press Ctrl+J. The website should now report Ctrl+Shift+J again.

By following these steps, you can reliably reproduce the bug and test any potential fixes.

Environment Details: Diving into the Configuration

Understanding the environment where the bug occurs is essential for finding a solution. The original bug report provides some key details:

  • Operating Systems: The issue occurs when connecting from macOS to a remote Linux OS.
  • Remote Desktop Protocol (RDP): The connection is established using RDP.
  • Kitty Terminal: The bug is specific to the Kitty terminal emulator.
  • Default Kitty Configuration: The user reports that the issue persists even with the default Kitty configuration (kitty --config NONE).

The fact that the bug occurs with the default Kitty configuration is significant. It suggests that the issue isn't related to custom keybindings or settings within Kitty. Instead, it points towards a more fundamental problem with how Kitty interacts with RDP or the keyboard input system.

Analyzing the Debug Output

The debug output provided in the bug report is a goldmine of information. Let's break it down piece by piece:

[95.557] Press xkb_keycode: 0x25 clean_sym: Control_L composed_sym: Control_L mods: capslock glfw_key: 57442 (LEFT_CONTROL) xkb_key: 65507 (Control_L)
[95.557] on_key_input: glfw key: 0xe062 native_code: 0xffe3 action: PRESS mods: ctrl+capslock text: '' state: 0 ignoring as keyboard mode does not support encoding this event
[95.675] Press xkb_keycode: 0x32 clean_sym: Shift_L composed_sym: Shift_L mods: ctrl+capslock glfw_key: 57441 (LEFT_SHIFT) xkb_key: 65505 (Shift_L)
[95.675] on_key_input: glfw key: 0xe061 native_code: 0xffe1 action: PRESS mods: ctrl+shift+capslock text: '' state: 0 ignoring as keyboard mode does not support encoding this event
[95.675] Press xkb_keycode: 0x2c clean_sym: j composed_sym: j mods: ctrl+shift+capslock glfw_key: 106 (j) xkb_key: 106 (j)
[95.675] on_key_input: glfw key: 0x6a native_code: 0x6a action: PRESS mods: ctrl+shift+capslock text: '' state: 0
KeyPress matched action: scroll_line_down, handled as shortcut
[95.808] Release xkb_keycode: 0x2c clean_sym: j mods: ctrl+shift+capslock glfw_key: 106 (j) xkb_key: 106 (j)
[95.808] on_key_input: glfw key: 0x6a native_code: 0x6a action: RELEASE mods: ctrl+shift+capslock text: '' state: 0 ignoring release event for previous press that was handled as shortcut
[95.822] Release xkb_keycode: 0x25 clean_sym: Control_L mods: ctrl+shift+capslock glfw_key: 57442 (LEFT_CONTROL) xkb_key: 65507 (Control_L)
[95.822] on_key_input: glfw key: 0xe062 native_code: 0xffe3 action: RELEASE mods: shift+capslock text: '' state: 0 ignoring as keyboard mode does not support encoding this event
[95.822] Release xkb_keycode: 0x32 clean_sym: Shift_L mods: shift+capslock glfw_key: 57441 (LEFT_SHIFT) xkb_key: 65505 (Shift_L)
[95.822] on_key_input: glfw key: 0xe061 native_code: 0xffe1 action: RELEASE mods: capslock text: '' state: 0 ignoring as keyboard mode does not support encoding this event

Here are some key observations:

  • mods: ctrl+capslock: This indicates that the Caps Lock key is being factored into the modifier state. This is a crucial clue, given the bug's interaction with Caps Lock.
  • mods: ctrl+shift+capslock: When the bug occurs, the modifier state includes Ctrl, Shift, and Caps Lock. This confirms that the Shift key is being incorrectly registered.
  • KeyPress matched action: scroll_line_down, handled as shortcut: This line shows that Kitty is interpreting Ctrl+Shift+J as a shortcut (scroll_line_down), which is the default behavior for that key combination.
  • ignoring as keyboard mode does not support encoding this event: This message suggests that Kitty's keyboard input handling might be having trouble encoding certain key events when Caps Lock is involved.

This debug output strongly suggests that the Caps Lock key is playing a central role in the bug. It seems to be influencing the modifier state in a way that causes the Shift key to be incorrectly registered.

Potential Solutions and Workarounds

Now that we have a good understanding of the bug, let's explore some potential solutions and workarounds:

  1. Check Keyboard Layouts:

    • Local Machine (macOS): Ensure your keyboard layout in macOS settings is correctly set to your physical keyboard layout.
    • Remote Machine (Linux): Verify the keyboard layout on the remote Linux machine as well. Use the setxkbmap command or your distribution's settings to configure the layout.
    • RDP Settings: Some RDP clients allow you to specify keyboard synchronization options. Check if there are any settings related to keyboard layout or input handling.

    A mismatch in keyboard layouts can lead to incorrect key interpretations. Making sure both machines and the RDP connection are using the correct layouts is a crucial first step.

  2. Kitty Configuration:

    • map Command: Kitty's configuration file allows you to remap key combinations using the map command. You could try explicitly mapping Ctrl+J to the desired action to override the incorrect interpretation.
    • Keyboard Protocol: Kitty has different keyboard protocol settings. Experiment with different settings in your kitty.conf file to see if one resolves the issue. You might try explicitly setting keyboard_protocol to x11 or glfw.

    While the bug occurs with the default configuration, explicitly mapping the key combination or tweaking keyboard protocol settings might provide a workaround.

  3. RDP Client Alternatives:

    • Different RDP Client: Try using a different RDP client on your macOS machine. Some clients might handle keyboard input differently and avoid the bug.
    • Other Remote Access Tools: Explore alternative remote access tools like SSH with X11 forwarding or VNC. These tools might have different keyboard handling mechanisms that circumvent the issue.

    The problem might lie within the specific RDP client you're using. Trying different clients or remote access methods can help isolate the source of the bug.

  4. Caps Lock Workaround (Temporary):

    • As the bug report suggests, toggling Caps Lock twice can temporarily resolve the issue. While not a permanent solution, this can be a quick workaround when the bug occurs.

    This workaround highlights the Caps Lock key's involvement in the bug and can be used while seeking a more permanent fix.

  5. Report the Bug to Kitty Developers:

    • If none of the above solutions work, consider reporting the bug to the Kitty developers on the project's GitHub page. Provide detailed information about your environment, steps to reproduce the bug, and any debug output you have.

    Reporting the bug ensures that the developers are aware of the issue and can work on a proper fix in future releases.

Conclusion: Taming the Ctrl+J Gremlin

The Ctrl+J to Ctrl+Shift+J bug in Kitty when using RDP is a frustrating issue, but by understanding the environment, analyzing debug logs, and exploring potential solutions, we can work towards resolving it. Remember to check your keyboard layouts, experiment with Kitty configuration options, consider alternative RDP clients, and report the bug to the developers if needed.

Hopefully, this deep dive has given you a solid understanding of the issue and equipped you with the knowledge to tackle it. Happy coding, and may your keyboard shortcuts always work as expected!