static L<Pt> allPointsInRect_virtual(int w, int h) {
  ret virtualList(i -> pt(i%w, i/w), w*h);
}

static L<Pt> allPointsInRect_virtual(int x, int y, int w, int h) {
  ret virtualList(i -> pt(x+i%w, y+i/w), w*h);
}

static L<Pt> allPointsInRect_virtual(Rect r) {
  ret allPointsInRect_virtual(r.x, r.y, r.w, r.h);
}

Began life as a copy of #1033584