Rendering to Terminal

A terminal-based editor renders to a 2D grid.

Terminal escape codes:

• \x1b[H: move cursor to top-left.
• \x1b[<row>;<col>H: move to (row, col).
• \x1b[2J: clear screen.
• \x1b[K: clear to end of line.
• \x1b[31m: red foreground.
• \x1b[44m: blue background.
• \x1b[0m: reset.

ANSI 256-color: \x1b[38;5;Nm for foreground. True color: \x1b[38;2;R;G;Bm.

Raw vs canonical mode:

• Canonical: terminal buffers input until Enter, processes ^C, etc.
• Raw: every keystroke immediately to app.
• Editor needs raw mode.

Reading keys:

• Single char: returned directly.
• Arrow keys: 3-byte escape sequence \x1b[A (up), \x1b[B (down), \x1b[C (right), \x1b[D (left).
• Function keys, Home, End: longer sequences.

Handling resize: SIGWINCH signal. Re-query terminal size, redraw.

Window query:

Render strategies:

• Naive: redraw entire screen on every keystroke. Slow + flicker.
• Incremental: track dirty regions, redraw only those.
• Double-buffer: build full frame in memory, blit at once.
• Diff: compare with previous frame, only update changed cells.

Modern: ratatui (Rust), tcell (Go), curses (Python) handle this.

Syntax highlighting:

• Lex source code into tokens (keyword, string, comment, etc.).
• Color each token.
• Tree-sitter is the modern way.