Editor (src/editor.c)

Key functions and behavior:

• get_line_start(line) — Return buffer offset for the start of logical line line.
• get_line_length_at_off(off) — Return number of characters on the line starting at buffer offset off (excludes newline).
• cursor_to_offset() — Convert editor_cursor_x/editor_cursor_y to a buffer offset.
• insert_char_at(off, ch) — Insert ch at buffer offset off, shifting contents and updating state.
• delete_char_before(off) — Delete character before offset off (backspace semantics).
• editor_draw() — Redraw title bar, visible text window, cursor and status bar.
• editor_open(fname, mode) — Load fname into the editor buffer and switch to editor mode.
• editor_handle_key(key, mode) — Handle navigation, editing, and save/exit shortcuts (Ctrl+S/Ctrl+X).
• editor_set_cursor_pos(x, y) — (optional, EDITOR_MOUSE_SUPPORT) Map a mouse click to editor cursor coordinates and clamp safely.

Source: src/editor.c