#The screen

import "@deckyard/zmachine/" as zmachine;

A Z-machine screen has two windows. The lower one scrolls and holds the story; the upper one is a fixed grid the game draws into, mostly for a status line.

#The lower window

output(m) is the text the lower window received since the last call that ran the game, with "\n" line breaks. The machine does not wrap lines: a console host wraps them to its width, a chat bot leaves that to the client. Styles (bold, italic, fixed pitch) and colours are dropped.

#The upper window

upperWindow(m) is the upper window, one string per row, each as wide as the screen. It keeps its content between turns, as on a real screen.

From version 4 on, the game draws it, usually as a one-line status bar. Up to version 3 the interpreter draws the status line, so the first row is built from the game's globals: the location on the left, the score and moves (or the time, for games that keep time) on the right.

def rows as list of string init zmachine.upperWindow($m);
if (len($rows) > 0) {
    io.printf("[%s]\n", $rows[0]);
}

#Screen size

setScreen(m, columns, rows) sets what the game sees, 80 by 255 by default. 255 rows tell the game the screen never fills, so it never pauses for a key. Games read the size when they start; set it before the first run.