Tmux-Resurrect: Fix White Lines On Prompt After Restore

Tmux-Resurrect is a fantastic tool for saving and restoring Tmux sessions, but like any software, it can sometimes present unexpected issues. One such issue reported by users involves the appearance of white lines on every prompt after restoring a session, specifically when using readline. This article delves into the problem, its potential causes, and possible solutions, offering a comprehensive guide for Tmux users facing this glitch.

Understanding the Issue

The primary issue reported is that after restoring a Tmux session using Tmux-Resurrect, a white line appears above each new command prompt. This extra line disrupts the visual flow of the terminal and can be quite annoying. The user who reported this issue also noted that hitting Enter to create a new prompt resolves the problem temporarily, but the white line reappears after each subsequent restoration.

Additionally, there's a related observation about prompt decorations, specifically when using tools like Starship. The prompt, which is normally displayed on a single line, gets rendered on two lines after restoration. This seems to be connected to the plugin storing the width of the main monitor, especially in multi-monitor setups. When the main monitor has a larger width, this can lead to display issues in smaller terminal windows.

Impact on User Experience

This issue significantly impacts the user experience. Imagine working on a project where you frequently save and restore your Tmux sessions to maintain your workflow. The persistent white lines clutter the terminal, making it harder to read and manage output. For users who rely on clean and efficient terminal environments, this visual disruption can be a major hindrance.

Initial Observations

From the initial report, we can gather a few key observations:

• White lines appear only after restoring a session: This suggests the issue is tied to the restoration process itself, rather than a general configuration problem.
• Hitting Enter temporarily fixes it: This workaround indicates the problem might be related to how the terminal redraws the prompt after a command is executed.
• Prompt decoration issues in multi-monitor setups: This points to potential problems with how Tmux-Resurrect handles different screen sizes and resolutions.

Potential Causes

To effectively troubleshoot this issue, it's important to explore the potential causes. Several factors could contribute to the appearance of white lines and the misrendering of prompts.

Terminal Redraw Issues

One possibility is that Tmux-Resurrect isn't correctly restoring the terminal's state, particularly regarding how it handles the prompt. The readline library, used by many shells (like Bash and Zsh), manages the input line and prompt display. If Tmux-Resurrect doesn't properly restore the terminal's state related to readline, it could lead to rendering glitches.

• Incorrect Terminal Size: Tmux-Resurrect might be saving and restoring the terminal size incorrectly. When the restored terminal size doesn't match the actual window size, it can cause display issues, including extra lines and misaligned prompts.
• Incomplete State Restoration: Tmux-Resurrect might not be saving and restoring all the necessary terminal state variables. This could leave the terminal in a state where it doesn't correctly handle prompt rendering, leading to the white line issue.

Prompt Configuration Problems

Another potential cause lies in the configuration of the prompt itself. Tools like Starship allow users to customize their terminal prompts with various decorations and information. If these customizations aren't handled correctly during restoration, it could lead to rendering issues.

• Starship Configuration: If Starship or similar tools are configured in a way that relies on specific terminal settings, restoring a session might not correctly reinstate these settings, causing the prompt to render incorrectly.
• Multi-line Prompts: Prompts that span multiple lines can be particularly problematic. If the terminal size or other settings aren't correctly restored, these multi-line prompts might not render as expected, leading to extra lines or other visual glitches.

Multi-Monitor Issues

The user's observation about multi-monitor setups points to another important area to consider. Tmux-Resurrect might not be handling different screen sizes and resolutions effectively, especially when moving between monitors with different dimensions.

• Incorrect Width Storage: The plugin might be storing the width of the main monitor and applying it to all restored sessions. This can lead to prompts and other terminal elements being rendered incorrectly in smaller windows or on different monitors.
• Screen Size Mismatch: When restoring a session on a monitor with a different resolution or size, the terminal might not adjust correctly, causing layout and rendering issues.

Troubleshooting Steps

Now that we've identified potential causes, let's explore some troubleshooting steps to resolve the issue. These steps are designed to help you pinpoint the exact problem and implement the appropriate solution.

1. Update Tmux and Tmux-Resurrect

Before diving into more complex solutions, ensure you're using the latest versions of Tmux and Tmux-Resurrect. Newer versions often include bug fixes and improvements that can address rendering issues.

• Tmux: Check your Tmux version by running tmux -V. If you're not on the latest version, update it using your system's package manager (e.g., apt update && apt upgrade tmux on Debian/Ubuntu).
• Tmux-Resurrect: Update Tmux-Resurrect using your plugin manager (e.g., TPM). This usually involves running a command like prefix + I (where prefix is your Tmux prefix key, often Ctrl+b) followed by :source-file ~/.tmux.conf and :resurrect.

2. Review Tmux Configuration

Your Tmux configuration file (~/.tmux.conf) might contain settings that are causing conflicts or issues with Tmux-Resurrect. Review your configuration for any potentially problematic settings.

• Conflicting Plugins: Ensure there are no conflicts between Tmux-Resurrect and other plugins you're using. Try disabling other plugins temporarily to see if the issue persists.
• Terminal Settings: Check for any custom terminal settings that might be interfering with prompt rendering. Pay close attention to settings related to terminal size, colors, and character encoding.

3. Investigate Prompt Configuration

If you're using a custom prompt tool like Starship, the issue might be related to its configuration. Investigate how Starship interacts with Tmux and Tmux-Resurrect.

• Starship Version: Ensure you're using the latest version of Starship. Outdated versions might have bugs that cause rendering issues.
• Starship Configuration: Review your Starship configuration file (~/.config/starship.toml) for any settings that might be causing problems. Try simplifying your prompt configuration to see if the white lines disappear.

4. Check Environment Variables

Environment variables can influence how the terminal and shell behave. Ensure there are no environment variables that might be interfering with prompt rendering.

• $TERM Variable: The $TERM variable specifies the terminal type. Ensure it's set to a valid value (e.g., xterm-256color). Incorrect values can lead to display issues.
• Locale Settings: Locale settings can affect character encoding and display. Ensure your locale is configured correctly (e.g., en_US.UTF-8).

5. Test with a Minimal Tmux Configuration

To isolate the issue, try using a minimal Tmux configuration. This involves creating a new Tmux configuration file with only the essential settings.

• Create a Backup: Back up your existing ~/.tmux.conf file.
• Create a Minimal Configuration: Create a new ~/.tmux.conf file with minimal settings, such as basic keybindings and plugin loading.
• Test Tmux-Resurrect: Save and restore a Tmux session using this minimal configuration. If the white lines disappear, the issue is likely related to your original configuration.

6. Examine Tmux-Resurrect Logs

Tmux-Resurrect might generate logs that provide clues about what's happening during the save and restore process. Examine these logs for any error messages or warnings.

• Log Location: Check the Tmux-Resurrect documentation or settings for the location of the log files.
• Analyze Logs: Look for any messages related to terminal size, prompt rendering, or state restoration. These messages might provide insights into the cause of the issue.

Possible Solutions

Based on the troubleshooting steps and potential causes, here are some possible solutions to address the white line issue in Tmux-Resurrect.

1. Implement Terminal Size Restoration Fixes

If the issue is related to incorrect terminal size restoration, you might need to implement fixes in your Tmux configuration or in Tmux-Resurrect itself (if you're comfortable with contributing to the plugin).

• Tmux Configuration: Add settings to your ~/.tmux.conf file to explicitly set the terminal size during session creation and restoration. This might involve using commands like tmux resize-pane or tmux set-window-option. For example:

  bind-key r source-file ~/.tmux.conf \; display "~/.tmux.conf reloaded."
  set -g default-terminal "xterm-256color"
  set -ga terminal-overrides ",*256col*:Tc:smcup@:rmcup@"
  # Fix for resizing panes
  bind-key | split-window -h
  bind-key - split-window -v
  
  # Smart pane switching with awareness of Vim splits.
  is_vim="ps -o state= -o comm= -t '#{pane_tty}' \| grep -iqE '^[^T]* (n\\/vim)""
  bind-key -n C-h if-shell "$is_vim" "send-keys C-h"  "select-pane -L"
  bind-key -n C-j if-shell "$is_vim" "send-keys C-j"  "select-pane -D"
  bind-key -n C-k if-shell "$is_vim" "send-keys C-k"  "select-pane -U"
  bind-key -n C-l if-shell "$is_vim" "send-keys C-l"  "select-pane -R"
  tmux_version='$(tmux -V | cut -d ' ' -f 2)'
  if [[ "$(vercomp "$tmux_version" 3.0) -ge 0 ]]; then
      bind-key -n C-\\ if-shell "$is_vim" "send-keys C-\\