svoid jTextPane_shrinkTextSizeToFillParentHeight(JTextPane pane, O... _) {
  if (pane == null || getParent(pane) == null) ret with callF(optPar onDone(_));
  swing {
    int pref = preferredHeight(pane);
    int h = getParentHeight(pane);
    double ratio = doubleRatio(h, pref);
    if (ratio >= 1) ret with callF(optPar onDone(_));
    float size = pane.getFont().getSize2D();
    float newSize = size-1;
    if (boolPar debug(_)) print("pref=" + pref + ", h=" + h + ", new font size: " + newSize);
    setFontSize(pane, newSize);
    awtLater(optPar delay(_, 50), r {
      jTextPane_shrinkTextSizeToFillParentHeight(pane, _);
    });
  }
}

Began life as a copy of #1023001