protected void updateCloseButtonMargins() {
		// scale close button margins
		_closeButtonLeftMargin = scale( closeButtonLeftMarginUnscaled );
		_closeButtonRightMargin = scale( closeButtonRightMarginUnscaled );

		// since close button size is hardcoded to 16x16 in NoFocusButton.getPreferredSize(),
		// add difference between scaled and unscaled close button size to margins
		int offset = (closeIcon.getIconWidth() - 16) / 2;
		_closeButtonLeftMargin += offset;
		_closeButtonRightMargin += offset;
	}
Actually does nearly the same as super.paintContentBorder() but
  - not invoking paintContentBorder*Edge() methods
  - repaint selection
flatlaf-jide-oss/src/main/java/com/formdev/flatlaf/jideoss/ui/FlatJideTabbedPaneUI.java