AsciiBlockMarginLR.java

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 * Original Author:  Arnaud Roques
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package net.sourceforge.plantuml.asciiverse;

// A generic AsciiBlock decorator: wraps another AsciiBlock and pads it with a
// fixed number of blank columns on the left and/or right. The inner block
// never knows it's been padded — asciiDraw() just moves it right by
// marginLeft, and asciiDimension() grows to include both margins — so any
// AsciiBlock (a Display, an ANote, another decorator, ...) can gain a margin
// without changing its own drawing logic. Same composition principle as
// every other AsciiBlock in this package: the caller
// asks the wrapper for its size, never recomputes the padding by hand.
public final class AsciiBlockMarginLR implements AsciiBlock {

	private final AsciiBlock inner;
	private final int marginLeft;
	private final int marginRight;

	AsciiBlockMarginLR(AsciiBlock inner, int marginLeft, int marginRight) {
		if (marginLeft < 0 || marginRight < 0)
			throw new IllegalArgumentException();

		this.inner = inner;
		this.marginLeft = marginLeft;
		this.marginRight = marginRight;
	}

	@Override
	public ADimension2D asciiDimension() {
		final ADimension2D dim = inner.asciiDimension();
		if (dim.getWidth() == 0)
			// An empty inner block (e.g. an unlabeled message) stays empty:
			// there's no text to pad around, so no margin is reserved either.
			return dim;

		return dim.delta(marginLeft + marginRight, 0);
	}

	@Override
	public void asciiDraw(InfinitePlan plan) {
		inner.asciiDraw(plan.move(marginLeft, 0));
	}

}