This article details a series of significant enhancements and refactorings applied to the Kilo text editor, built with Go. The improvements span from foundational code organization to sophisticated user interface controls and robust error handling, aiming to create a more modular, efficient, and user-friendly terminal-based editor.

Refined Module Structure and Utilities

The initial steps involved streamlining the project’s internal organization. The exit module, which primarily housed program termination logic, was refactored and renamed to utils. This change reflects its expanded role, now encompassing a broader range of helper functions that support various aspects of the editor’s operation.

A key utility introduced is the SafeExit function. Beyond simply exiting, this function now gracefully clears the terminal screen and repositions the cursor to the top-left before the program terminates. This ensures a clean exit experience, preventing residual text or cursor placement from cluttering the user’s terminal. Additionally, a new CtrlKey function was implemented within the utils module to correctly interpret control key combinations, allowing the editor to respond to Ctrl-Q for quitting, a common and intuitive command, rather than a simple ‘q’.

Centralized Editor Logic and Input Processing

To improve modularity and manage the editor’s state more effectively, a dedicated editor package was created. This package now encapsulates all core editor logic, including the EditorConfig struct which holds essential editor state like the terminal’s restore function, a buffered reader for input, and the dynamically determined window dimensions.

The main.go file was simplified, primarily focusing on initializing the Unix raw mode for terminal control and then handing over execution to the editor.NewEditor and editor.EditorLoop functions. The EditorLoop continuously processes user input via editorProcessKeypress, which in turn calls editorReadKey to read individual bytes from standard input. This architectural change clearly separates the editor’s operational cycle from the application’s bootstrapping, making the codebase easier to understand and maintain.

Advanced Terminal Output and UI Enhancements

Significant effort was invested in controlling terminal output for a smoother user experience:

• Screen Clearing and Cursor Repositioning: The editor now leverages VT100 escape sequences to clear the screen and reposition the cursor. Instead of clearing the entire screen at once, the editorRefreshScreen function, in conjunction with editorDrawRows, now clears each line individually as it’s redrawn (ESC[K), ensuring a consistent and flicker-free update. The cursor is also repositioned to ESC[H (row 1, column 1) after each refresh.
• Flicker Prevention with AppendBuffer: To combat screen flickering, a custom AppendBuffer was implemented. Instead of directly writing multiple Fprintf calls to os.Stdout, all output for a screen refresh is first accumulated in this buffer. Once all drawing operations are complete, the entire buffer’s content is written to the terminal in a single, efficient operation. This drastically reduces the number of I/O calls, eliminating visual artifacts.
• Cursor Visibility Control: During screen repainting, the cursor is temporarily hidden (ESC[?25l) and then made visible again (ESC[?25h) after the refresh is complete. This subtle enhancement further reduces perceived flickering and provides a more polished visual experience.
• Dynamic Row Drawing and Tildes: The editor now dynamically determines the terminal’s window size using utils.GetWindowSize. This allows it to adapt to different terminal dimensions, rendering tildes (~) on all lines beyond the file content to mimic the aesthetic of editors like Vim, adapting precisely to the available screen height.
• Welcome Message and Centering: A welcome message, “Kilo editor — version X.X.X”, is now displayed when the editor starts. This message is dynamically centered horizontally on the screen, appearing approximately one-third of the way down. The centering logic intelligently handles messages that might be longer than the terminal’s width, ensuring it remains within bounds.

Enhanced Robustness: Logging and Window Sizing

Beyond user interface improvements, the editor’s robustness was also a focus:

• Dynamic Window Sizing: The utils.GetWindowSize function queries the operating system for the terminal’s current row and column dimensions. This allows the editor to dynamically adjust its display, making it responsive to terminal resizing and ensuring content fills the available space correctly.
• Comprehensive Logging: A logging mechanism was integrated using Go’s log/slog package. The utils.CreateLoggerFile function creates a dated log file within a kilo-go subdirectory of the user’s configuration directory. This setup enables detailed debugging and error tracking, saving valuable information to a persistent file without interfering with the terminal’s display. The logger is initialized at program startup, ready to capture events from the outset.

These combined enhancements represent a significant leap in the Kilo editor’s functionality and user experience, laying a solid foundation for future development while demonstrating best practices in terminal application design.