static Rect textComponent_substringRect(final JTextComponent tc, final int startIndex, final int endIndex) {
  ret swing(func -> Rect {
    mergeRects(toRect(tc.modelToView(startIndex)), toRect(tc.modelToView(endIndex)))
  });
}

static Rect textComponent_substringRect(final JTextComponent tc, IntRange charRange) {
  ret charRange == null ? null
    : textComponent_substringRect(tc, charRange.start, charRange.end);
}