static int hstackWithSpacing_spacing = 10;

// first part can be spacing value
static JPanel hstackWithSpacing(O... parts) {
  parts = flattenArray2(parts); // allow collections in parameters
  int spacing = hstackWithSpacing_spacing;
  int i = 0;
  if (first(parts) instanceof Int) {
    spacing = toInt(first(parts));
    ++i;
  }
  JPanel panel = new JPanel(new GridBagLayout);
  new GridBagConstraints gbc;
  gbc.weighty = 1;
  gbc.fill = GridBagConstraints.VERTICAL;
  gbc.gridheight = GridBagConstraints.REMAINDER;
  for (; i < l(parts); i++) {
    if (i != 0)
      panel.add(javax.swing.Box.createRigidArea(new Dimension(spacing, 0)), gbc);
    panel.add(wrapForSmartAdd(parts[i]), gbc);
  }
  gbc.weightx = 1;
  panel.add(jrigid(), gbc);
  ret panel;
}

Began life as a copy of #1007328