plugins/org.eclipse.app4mc.amalthea.visualizations.standard/src/org/eclipse/app4mc/amalthea/visualizations/standard/util/FontMetrics.java

/*********************************************************************************
 * Copyright (c) 2020 Robert Bosch GmbH and others.
 *
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Robert Bosch GmbH - initial API and implementation
 ********************************************************************************
 */
package org.eclipse.app4mc.amalthea.visualizations.standard.util;

import javafx.geometry.Bounds;
import javafx.scene.text.Font;
import javafx.scene.text.Text;

/**
 * Helper class to calculate metrics based on a {@link Font}.
 */
public class FontMetrics {

	private final Text internal = new Text();
	public final double lineHeight;
	public final double ascent;
	public final double descent;

	/**
	 * Create a new {@link FontMetrics} object for the given {@link Font}.
	 *
	 * @param font The {@link Font} for which the {@link FontMetrics} class should
	 *             be created.
	 */
	public FontMetrics(Font font) {
		internal.setFont(font);
		Bounds bounds = internal.getLayoutBounds();
		lineHeight = bounds.getHeight();
		ascent = -bounds.getMinY();
		descent = bounds.getMaxY();
	}

	/**
	 * The width needed for a given text.
	 *
	 * @param txt The text for which the width is requested.
	 * @return The width of the given text for the configured {@link Font}.
	 */
	public double computeStringWidth(String txt) {
		internal.setText(txt);
		return internal.getLayoutBounds().getWidth();
	}
}