Checkbox Fade

// Checkbox Fade
// Apply to Opacity
// Add a Checkbox Control named "Show"

fadeDur = 0.5;   // Fade length in seconds

chk = effect("Show")("Checkbox");
out = chk.value * 100;
if (chk.numKeys > 0) {
  n = chk.nearestKey(time).index;
  if (chk.key(n).time > time) n = n - 1;
  if (n < 1) {
    // Before the first key, AE holds that key's value
    out = chk.key(1).value * 100;
  } else {
    // Walk the keys so an interrupted fade stays continuous:
    // each fade starts from wherever the previous fade actually reached.
    cur = chk.key(1).value * 100;
    for (i = 1; i <= n; i++) {
      target = chk.key(i).value * 100;
      if (i < n) {
        tEval = chk.key(i + 1).time;
      } else {
        tEval = time;
      }
      cur = linear(tEval - chk.key(i).time, 0, fadeDur, cur, target);
    }
    out = cur;
  }
}
out;