Java tutorial
/* * This library is part of OpenCms - * the Open Source Content Management System * * Copyright (c) Alkacon Software GmbH (http://www.alkacon.com) * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * For further information about Alkacon Software GmbH, please see the * company website: http://www.alkacon.com * * For further information about OpenCms, please see the * project website: http://www.opencms.org * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ package org.opencms.gwt.client.util; import java.util.HashMap; import java.util.Map; import com.google.gwt.dom.client.Element; import com.google.gwt.dom.client.Style; import com.google.gwt.user.client.DOM; import com.google.gwt.user.client.ui.RootPanel; /** * Provides precise pixel measurements for blocks of text so that you can * determine exactly how high and wide, in pixels, a given block of text will * be.<p> * * Normal usage would be: * <pre> * for(Element e: elements) { * CmsTextMetrics tm = CmsTextMetrics.get(e, "TextMetricsKey"); * * // measure text * if (r.getWidth(text) > 500) { * // do something * } * // release * tm.release(); * } * </pre> * * Based on <a href="http://code.google.com/p/my-gwt/source/browse/trunk/user/src/net/mygwt/ui/client/util/TextMetrics.java">my-gwt TextMetrics</a>.<p> * * @since 8.0.0 */ public final class CmsTextMetrics { /** Default attributes to bind. */ private static final CmsDomUtil.Style[] ATTRIBUTES = new CmsDomUtil.Style[] { CmsDomUtil.Style.fontSize, CmsDomUtil.Style.fontSizeAdjust, CmsDomUtil.Style.fontFamily, CmsDomUtil.Style.fontStretch, CmsDomUtil.Style.fontStyle, CmsDomUtil.Style.fontVariant, CmsDomUtil.Style.fontWeight, CmsDomUtil.Style.letterSpacing, CmsDomUtil.Style.textAlign, CmsDomUtil.Style.textDecoration, CmsDomUtil.Style.textIndent, CmsDomUtil.Style.textShadow, CmsDomUtil.Style.textTransform, CmsDomUtil.Style.lineHeight, CmsDomUtil.Style.whiteSpace, CmsDomUtil.Style.wordSpacing, CmsDomUtil.Style.wordWrap, CmsDomUtil.Style.padding }; /** The map containing the instances. */ private static Map<String, CmsTextMetrics> m_instances = new HashMap<String, CmsTextMetrics>(); /** The playground. */ private Element m_elem; /** The text metrics key. */ private String m_key; /** * Internal constructor for creating a text metrics object with a given key.<p> * * @param key the key identifying the text metrics. */ private CmsTextMetrics(String key) { m_key = key; } /** * Gets the text metrics object for a given DOM element and key.<p> * * If the key is null, or the method has been never called with the same key * before, a new text metrics object will be created, with its style taken from * the element parameter. Otherwise, the text metrics object for the given key will * be returned, and the element parameter will be ignored. * * @param element the element from which to take the style * @param key the text metrics key * * @return a text metrics object */ public static CmsTextMetrics get(Element element, String key) { CmsTextMetrics instance = null; if (key == null) { instance = new CmsTextMetrics(key); instance.bind(element); } else { instance = m_instances.get(key); if (instance == null) { instance = new CmsTextMetrics(key); instance.bind(element); m_instances.put(key, instance); } } return instance; } /** * Returns the measured height of the specified text. For multiline text, be * sure to call {@link #setFixedWidth} if necessary.<p> * * @param text the text to be measured * @return the height in pixels */ public int getHeight(String text) { m_elem.setInnerText(text); return CmsDomUtil.getCurrentStyleInt(m_elem, CmsDomUtil.Style.height); } /** * Returns the measured width of the specified text.<p> * * @param text the text to measure * @return the width in pixels */ public int getWidth(String text) { m_elem.setInnerText(text); return CmsDomUtil.getCurrentStyleInt(m_elem, CmsDomUtil.Style.width); } /** * Should be called, when finished measuring, to release the playground.<p> */ public void release() { if (m_key == null) { m_elem.removeFromParent(); m_elem = null; } // if we have a key, we do nothing so that the instance can be reused later } /** * Sets a fixed width on the internal measurement element. If the text will be * multiline, you have to set a fixed width in order to accurately measure the * text height.<p> * * @param width the width to set on the element */ public void setFixedWidth(int width) { m_elem.getStyle().setWidth(width, Style.Unit.PX); } /** * Binds this text metrics instance to an element from which to copy existing * CSS styles that can affect the size of the rendered text.<p> * * @param element the element */ protected void bind(Element element) { bind(element, ATTRIBUTES); } /** * Binds this text metrics instance to an element from which to copy existing * CSS styles that can affect the size of the rendered text.<p> * * @param element the element * @param attributes the attributes to bind */ protected void bind(Element element, CmsDomUtil.Style... attributes) { if (m_elem == null) { // create playground m_elem = DOM.createDiv(); Style style = m_elem.getStyle(); style.setVisibility(Style.Visibility.HIDDEN); style.setPosition(Style.Position.ABSOLUTE); style.setLeft(-5000, Style.Unit.PX); style.setTop(-5000, Style.Unit.PX); } // copy all relevant CSS properties Style style = m_elem.getStyle(); for (CmsDomUtil.Style attr : attributes) { String attrName = attr.toString(); style.setProperty(attrName, CmsDomUtil.getCurrentStyle(element, attr)); } // append playground RootPanel.getBodyElement().appendChild(m_elem); } }