/**
* Update the walkabout strengths and stay flags of all variables
* downstream of the given constraint. Answer a collection of
* unsatisfied constraints sorted in order of decreasing strength.
*/
function removePropagateFrom($out)
{
$out->determinedBy = null;
$out->walkStrength = Strength::Weakest();
$out->stay = true;
$unsatisfied = new OrderedCollection();
$todo = new OrderedCollection();
$todo->add($out);
while ($todo->size() > 0) {
$v = $todo->removeFirst();
for ($i = 0; $i < $v->constraints->size(); $i++) {
$c = $v->constraints->at($i);
if (!$c->isSatisfied()) {
$unsatisfied->add($c);
}
}
$determining = $v->determinedBy;
for ($i = 0; $i < $v->constraints->size(); $i++) {
$next = $v->constraints->at($i);
if ($next != $determining && $next->isSatisfied()) {
$next->recalculate();
$todo->add($next->output());
}
}
}
return $unsatisfied;
}
function recalculate()
{
$in = $this->input();
$out = $this->output();
$out->walkStrength = Strength::weakestOf($this->strength, $in->walkStrength);
$out->stay = $in->stay && $this->scale->stay && $this->offset->stay;
if ($out->stay) {
$this->execute();
}
// stay optimization
}
