Terminal raw mode and unbuffered input support (libc-free)

• Type: feature
• Status: done
• Owner: —
• Opened: 2026-06-21
• Closed: 2026-06-21
• Relation: Stresses terminal state configuration and unbuffered input handling. Blocker for feature-demo-file-browser and feature-demo-video-player.

Goal

Provide a statically-linked, libc-free terminal raw mode toggle in ansiterm to read keyboard events character-by-character without waiting for Enter.

Surface (sketch)

In lib/rtl/ansiterm.pas:

• procedure AnsiSetRawMode(enable: Boolean);
• function AnsiReadKey: Char; (or equivalent non-blocking read)

Implementation Steps

1. Bind the TCGETS and TCSETS constants (ioctl request codes) in the RTL.
2. Implement terminal state reading and writing via sys_ioctl (Syscall 16 on x86-64).
3. Implement AnsiSetRawMode which reads current state, clears ICANON and ECHO flags, sets minimum characters to 1, and writes back.
4. Restore standard terminal state upon program exit or crash (via an exit handler or try/finally).

Log

• 2026-06-21 — Opened.
• 2026-06-21 — Landed libc-free AnsiSetRawMode and AnsiReadKey in lib/rtl/ansiterm.pas, using raw syscall ioctl and fcntl to support unbuffered keyboard event reading. Tested in test/lib_ansiterm.pas (commit 14832e1).