VerticalSpacer

VerticalSpacer is a gap of exactly so many pixels.

cp.add(new VerticalSpacer(20));

It is a Div of the given height holding a non-breaking space, with its overflow hidden. That is all it is.

Use it where a gap is a one-off - between two panels on one screen, above a button bar. Where the same gap belongs everywhere, it belongs in the theme instead: a css class on the components around it says why there is space, and a spacer only says that there is.