Zellij: Fixing Size (Width) Application Issues

Experiencing issues with Zellij where the size (width) isn't being applied as expected? You're not alone! This article delves into a specific bug encountered with Zellij, a terminal workspace and multiplexer, focusing on the problem where the specified width isn't correctly applied when using sidekick.nvim. We'll explore the bug report, the steps to reproduce it, and a workaround that seems to solve the issue. If you're struggling with similar problems, read on to understand the issue better and potentially find a solution.

Understanding the Bug: Size (Width) Not Applied with Zellij

When working with terminal multiplexers like Zellij, correctly configuring window sizes is crucial for an efficient workflow. The initial bug report highlights a frustrating issue: the size (width) setting within sidekick.nvim, a Neovim plugin, doesn't apply correctly when using the Zellij backend. Specifically, the user attempted to set the width of a split window using the mux.split.size option, but the configuration was consistently ignored. This means that regardless of the specified size, the window would not adjust accordingly, leading to a suboptimal user experience.

Digging Deeper into the Configuration

The user's configuration attempts, as shown in the provided code snippet, illustrate the core of the problem. They tried setting mux.split.size with different values, including decimal percentages (e.g., 0.3) and absolute pixel values (e.g., 60), but neither approach yielded the desired result. This suggests that the direct size parameter might not be the correct way to influence the width when Zellij is in the mix. The user's initial setup looked like this:

{
    'folke/sidekick.nvim',
    opts = {
      cli = {
        mux = {
          backend = 'zellij',
          enabled = true,
          split = {
            vertical = true,
            -- size = 0.3, -- default: 0.5 -- NOT WORKING with zellij
            -- size = 60, -- NOT WORKING either
          },
        },
        win = {
          layout = 'right',
          split = {
            width = 0, -- Set to 0 so the default logic ignores it initially
          },
          -- The Magic Hook
          config = function(terminal)
            -- terminal.opts is a deepcopy of Config.cli.win
            -- We can calculate the integer width here dynamically
            terminal.opts.split.width = math.floor(vim.o.columns * 0.40)
          end,
        },
      },
      -- NES = Next Edit Suggestions: requires Copilot
      nes = { enabled = false },
    },
  },

Notice the commented-out size options. These are the initial attempts to control the width, which unfortunately didn't work. This led the user to explore alternative methods to achieve the desired window sizing within Zellij.

The Workaround: A Dynamic Approach

After some experimentation, the user discovered a workaround involving a dynamic calculation of the width. Instead of directly setting mux.split.size, they used a configuration function within the win section to calculate the width based on the current number of columns in the Neovim window. This approach, while a bit more involved, proved to be effective. The key part of the solution lies in this snippet:

config = function(terminal)
  terminal.opts.split.width = math.floor(vim.o.columns * 0.40)
end

Here, a function is defined that takes the terminal object as an argument. Inside this function, the split.width option is set to a value calculated by multiplying the total number of columns (vim.o.columns) by 0.40 (representing 40% of the screen width) and then rounding down to the nearest integer using math.floor. This dynamic calculation ensures that the width of the split window adjusts automatically whenever the Neovim window is resized, providing a more responsive and adaptable user experience. This workaround highlights the flexibility of Neovim's configuration system and the power of using dynamic calculations to overcome limitations.

Steps to Reproduce the Zellij Size Bug

To fully understand and potentially contribute to fixing this bug, it's crucial to be able to reproduce it consistently. The bug report provides a clear set of steps to follow:

1. Run Neovim inside a Zellij session: This is an important first step as the bug seems specific to the interaction between sidekick.nvim and Zellij.
2. Update or set mux.split.size: Modify your Neovim configuration to include the mux.split.size option within the sidekick.nvim settings. Try different values, such as decimal percentages (e.g., 0.3) or absolute values (e.g., 60), to see if any have an effect.
3. Quit or Ctrl-C any active CLI: Ensure that any active command-line interfaces (CLIs) spawned by sidekick.nvim are terminated. Double-check this by using zellij list-sessions to confirm that no lingering sessions are running.
4. Restart Neovim: Close and reopen Neovim to ensure that the configuration changes are fully applied.
5. Toggle a new CLI: Use the command or keybinding that triggers sidekick.nvim to open a new CLI window. This should reveal whether the mux.split.size setting has been correctly applied.

By following these steps, you should be able to observe the bug: the size of the split window will not match the value specified in mux.split.size. This consistent reproduction is essential for developers to investigate the root cause and implement a proper fix.

Expected Behavior vs. Actual Behavior

Understanding the discrepancy between the expected and actual behavior is key to grasping the impact of this bug. The expected behavior is that the size setting within the mux.split configuration should directly control the width of the split window created by sidekick.nvim when using Zellij. In other words, if you set size = 0.3, you would expect the split window to occupy 30% of the available screen width. Similarly, a value like size = 60 should translate to a window width of 60 columns.

However, the actual behavior deviates significantly from this expectation. As the bug report demonstrates, the size setting is effectively ignored when Zellij is the backend. The split window's width doesn't reflect the configured value, leading to an inconsistent and potentially disruptive user experience. This mismatch between expectation and reality highlights the importance of addressing this bug to ensure that users can rely on the configuration options provided by sidekick.nvim.

Diving Deeper: Analyzing the Repro Steps

The provided steps to reproduce the bug offer valuable clues about its potential causes. Let's break down each step and consider its significance:

1. Running Neovim inside a Zellij session: This suggests that the bug is likely related to the interaction between sidekick.nvim and Zellij specifically. It's possible that Zellij's window management mechanisms interfere with how sidekick.nvim attempts to set the window size.
2. Updating or setting mux.split.size: This confirms that the issue revolves around the mux.split.size configuration option. The fact that different values (percentages and absolute numbers) don't work points to a deeper problem with how this setting is being processed or applied.
3. Quitting or Ctrl-C any active CLI: This step ensures a clean state before testing the configuration. By killing any existing CLI sessions, you eliminate potential conflicts or interference from previous instances.
4. Restarting Neovim: Restarting Neovim forces the configuration to be reloaded, ensuring that the changes are applied correctly. This step is crucial for verifying that the issue isn't simply a matter of stale configuration.
5. Toggling a new CLI: This is the final step that reveals whether the mux.split.size setting has taken effect. If the window size doesn't match the configured value, it confirms the presence of the bug.

By carefully analyzing these steps, developers can narrow down the scope of the problem and focus their investigation on the areas most likely to be responsible for the bug. The fact that the issue only occurs within Zellij sessions suggests that the interaction between sidekick.nvim and Zellij's windowing system is the key area to examine.

Conclusion: Addressing the Zellij Size Bug

The bug where the size (width) isn't correctly applied with Zellij and sidekick.nvim presents a significant challenge for users seeking precise control over their terminal layouts. While the dynamic workaround provides a viable solution, a proper fix is essential to ensure a seamless and predictable experience. By understanding the bug, its reproduction steps, and the discrepancy between expected and actual behavior, we can contribute to a more robust and user-friendly Neovim environment.

If you're interested in learning more about Zellij, you can visit their official website: Zellij Website. This external resource offers comprehensive documentation, tutorials, and community support to help you master Zellij and enhance your terminal workflow.