mv_package

udt_curses

ncurses terminal handling for Rocket UniData, reached from UniBasic through CallC — so full-screen programs (editors like EB, menus, data entry) get reliable key and mouse handling over xterm / tmux / ssh instead of UniData's own flaky terminal layer.

It brings MVX's input model to UniData: KEYIN() returns keys by name — UP, F3, ENTER, PGUP, HOME, … — and mouse events arrive as coordinates, matching MVX's KEYIN() / MOUSE().

> UniData only, for now. The bridge is native ncurses compiled into > UniData's CallC library; there is nothing to install on MVX, which has > KEYIN() and MOUSE() built in.

What you get

A handful of CallC entry points, driven from BASIC:

| Call | Purpose | |------|---------| | CALLC CURSINIT("") | enter curses mode (raw keys, no echo, mouse on) | | CALLC CURSEND("") | leave curses mode, restore the terminal | | CALLC CURSDIM("") | "rows cols" of the screen | | CALLC CURSCURSOR("0") | cursor visibility ("0" hide, "1" normal) | | CALLC CURSCOLOR(spec) | text colour — "GREEN", "WHITE BLUE", "BRIGHT GREEN", "OFF" | | CALLC CURSBKGD(spec) | screen background (back-colour-erase) | | CALLC CURSMOVE("r c") | move the cursor (0-based) | | CALLC CURSADDSTR(t) | write text at the cursor | | CALLC CURSCLEAR("") / CURSCLREOL("") / CURSREFRESH("") | clear screen / clear to EOL / flush | | CALLC CURSTIMEOUT("ms") | read timeout for the next key ("-1" blocks) | | CALLC CURSKEY("") | one keystroke, as a logical name | | CALLC CURSMOUSE("") | last mouse event: col : @VM : row : @VM : button : @VM : event |

CURSKEY returns printable characters as themselves and named keys as UP DOWN LEFT RIGHT HOME END PGUP PGDN INS DEL BS TAB BTAB ENTER ESC F1..F12 MOUSE — the same vocabulary as MVX.

Is it installed? — optional-capability check

The bridge is a native add-on that may or may not be present. A program should ask before using it, and fall back cleanly when it is absent:

   $INCLUDE BP CURSES.INS
   IF CURSES.AVAIL("") THEN
      GOSUB FULLSCREEN.UI          ;* ncurses is here — use it
   END ELSE
      GOSUB PLAIN.UI               ;* runs on any account
   END

CURSES.AVAIL() is built on the generic CALLC.EXISTS(name), which reports whether any CallC function is registered — without invoking it (a CallC to an unregistered function aborts the whole program, so a live probe is impossible). It reads the canonical CallC definition the installer maintains, so it answers correctly even on an account where udt_curses was never installed. This primitive is general enough that it belongs in the package manager, available to every installed package.

See [BP/CURSES.DEMO](BP/CURSES.DEMO) for a complete probe-then-drive example.

Demos

DEMO.BP/ holds the MVX terminal demos ported to the curses API — the same programs, with KEYIN()/@(x,y)/COLOR()/MOUSE() swapped for the CALLC CURS… calls:

• [SNAKE](DEMO.BP/SNAKE) — arrows steer, food grows and speeds the

snake, walls or your tail end it. Timed CURSKEY, colour, dynamic-array body.

• [FSDEMO](DEMO.BP/FSDEMO) — Midnight-Commander dress: cyan menu bar,

blue field, function-key bar. Exercises HOME/END/PGUP/PGDN and colour.

• [MOUSE-DEMO](DEMO.BP/MOUSE-DEMO) — click or drag to draw, coloured by

button; the status line echoes col/row/button/event.

:CREATE.FILE DIR DEMO.BP
:BASIC DEMO.BP SNAKE
:RUN DEMO.BP SNAKE

Install

Needs gcc, ncurses-devel, and a UniData whose $UDTHOME/bin/work holds the standard CallC generators and link recipe.

export UDTHOME=/usr/ud83        # your UniData home
./install.sh                    # builds curscb.c into libu2callc.so

then catalog the BASIC API into each account that uses it:

:BASIC BP CALLC.EXISTS
:CATALOG BP CALLC.EXISTS LOCAL FORCE
:BASIC BP CURSES.AVAIL
:CATALOG BP CURSES.AVAIL LOCAL FORCE

UniData loads exactly one libu2callc.so, so native add-ons cannot each own it — they are aggregated. install.sh stages this package's contribution (udt-callc/) into $UDTHOME/callc.d/curses/ and then rebuilds the shared library from every contribution present, so installing curses never clobbers another add-on (e.g. the git bridge) and removing callc.d/curses + rebuilding drops it cleanly. The package manager (mv_package) does the same staging and rebuild when it installs the package — this script is the standalone path.

How it works

udt-callc/curscb.c wraps ncurses (initscr, getch with keypad, getmouse, …) as CallC functions. UniData's CallC marshals every argument and return value as a string, so integers travel as text and CURSKEY returns the decoded key name rather than a raw byte (binary would be truncated at the first NUL). keypad(TRUE) makes ncurses assemble terminal escape sequences into named keys using the terminfo database, which is why decoding is correct across terminal types where UniData's built-in handling is not.

Layout

udt-callc/curscb.c  the ncurses CallC bridge (C)
udt-callc/funcs     this package's cfuncdef fragment (its CallC declarations)
install.sh          stage udt-callc/ into $UDTHOME/callc.d and rebuild the lib
BP/CALLC.EXISTS     generic "is this CallC function registered?" probe
BP/CURSES.AVAIL     "is udt_curses installed?" (wraps CALLC.EXISTS)
BP/CURSES.INS       $INCLUDE: DEFFUN declarations + the API reference
BP/CURSES.DEMO      worked example: probe, then a live key/mouse screen
DEMO.BP/            the MVX terminal demos ported: SNAKE, FSDEMO, MOUSE-DEMO
PKG                 package descriptor (mv-package)

The udt-callc/ directory is the package's native contribution in the form mv_package's UniData builder consumes: C sources (or pre-built objects for a binary release), a funcs cfuncdef fragment, and an optional libs line of extra linker flags.

Status

Proven on UniData 8.3.2 TE: screen output, KEYIN-by-name (a UP ENTER TAB PGUP F1 HOME q), mouse (col:row:evt), timed reads, and coexistence with the git CallC bridge in the same library.

Licence

GPL-2.0-only. Copyright (C) 2026 Gordon Heydon.