persistable asclass AbstractSSIList<MySSI extends AbstractSSI> extends NotifyingList<MySSI> is StringIO {
  *() { init(); }
  *(Cl<? extends AbstractSSI> l) { initAndAddAll(importSSIs(l)); }
  
  L<MySSI> importSSIs(Cl<? extends AbstractSSI> l) {
    ret map importSSI(l);
  }
  
  abstract MySSI importSSI(AbstractSSI ssi);
  
  BufferedImage render(WidthAndHeight size) {
    ret renderAll(this, size);
  }
  
  BufferedImage render(BufferedImage canvas) {
    ret renderAll(this, canvas);
  }
  
  BufferedImage renderOutlines(WidthAndHeight size) {
    ret toSSIList().renderOutlines(size);
  }
  
  SSIList toSSIList() {
    ret new SSIList(map(this, -> .toSSI()));
  }
  
  public void readWrite(StringHead head) {
    head.exchangeAll(this);
  }
  
  L<VectorSSI> vectorSSIs() { ret instancesOf VectorSSI(this); }
  L<SSI> directSSIs aka literalSSIs() { ret instancesOf SSI(this); }
  
  Percent percentageVectorized() {
    ret Percent.ratio(l(vectorSSIs()), l(this));
  }
}