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.pragma library
// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// The wallpaper engine's order, tested by test_shuffle.js under node: a
// shuffle bag. Each round shows every path once in random order, and a new
// round never opens with the path on screen, so a reshuffle cannot show the
// same picture twice running.
// The next path and what is left of the round. `list` is what may be shown
// now, so a heart removed since the last draw drops out of the bag; `last` is
// the path on screen. pick is "" for an empty list.
function draw(list, bag, last) {
let left = bag.filter(p => list.indexOf(p) >= 0);
if (left.length === 0) left = shuffled(list, last);
return { pick: left.length ? left[0] : "", bag: left.slice(1) };
}
function shuffled(list, last) {
const a = list.slice();
for (let i = a.length - 1; i > 0; i--) {
const j = Math.floor(Math.random() * (i + 1));
const t = a[i]; a[i] = a[j]; a[j] = t;
}
if (a.length > 1 && a[0] === last) { const t = a[0]; a[0] = a[1]; a[1] = t; }
return a;
}
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