private void detailCallback() {
		showingDetails = !showingDetails;
		tree.setVisible(showingDetails);
		horizontalSpacer.setVisible(showingDetails);
		detailButton.setText(showingDetails ? CLOSE : DETAIL);
		repack();
	}
This spacer addresses the optical impression that the message panel changes size when showing details
Ghidra/Framework/Docking/src/main/java/docking/ErrLogExpandableDialog.java