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Rich Internet Application Framework for GWT
There is a newer version: 2.3.1-gwt22
/*
 * Sencha GXT 2.3.0 - Sencha for GWT
 * Copyright(c) 2007-2013, Sencha, Inc.
 * [email protected]
 * 
 * http://www.sencha.com/products/gxt/license/
 */
 package com.extjs.gxt.ui.client.util;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import com.extjs.gxt.ui.client.core.El;
import com.extjs.gxt.ui.client.core.XDOM;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;

/**
 * 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.
 */
public class TextMetrics {

  private static TextMetrics instance;

  /**
   * Returns the singleton instance.
   * 
   * @return the text metrics instance
   */
  public static TextMetrics get() {
    if (instance == null) {
      instance = new TextMetrics();
    }
    return instance;
  }

  private El el;

  private TextMetrics() {
    el = new El(DOM.createDiv());
    DOM.appendChild(XDOM.getBody(), el.dom);
    el.makePositionable(true);
    el.setLeftTop(-10000, -10000);
    el.setVisibility(false);
  }

  /**
   * Binds this TextMetrics instance to an element from which to copy existing
   * CSS styles that can affect the size of the rendered text.
   * 
   * @param el the element
   */
  public void bind(Element el) {
    bind(new El(el));
  }

  /**
   * Binds this TextMetrics instance to an element from which to copy existing
   * CSS styles that can affect the size of the rendered text.
   * 
   * @param el the element
   */
  public void bind(El el) {   
    //needed sometimes to force a refresh
    el.repaint();
    List l = new ArrayList();
    l.add("fontSize");
    l.add("fontWeight");
    l.add("fontStyle");
    l.add("fontFamily");
    l.add("lineHeight");
    l.add("textTransform");
    l.add("letterSpacing");

   
    Map map = el.getStyleAttribute(l);
    for (String key : map.keySet()) {
      this.el.setStyleAttribute(key, map.get(key));
    }
  }

  /**
   * Returns the measured height of the specified text. For multiline text, be
   * sure to call {@link #setFixedWidth} if necessary.
   * 
   * @param html the html content to be measured
   * @return the height in pixels
   */
  public int getHeight(String html) {
    return getSize(html).height;
  }

  /**
   * Returns the size of the specified text based on the internal element's
   * style and width properties.
   * 
   * @param html the html string to measure
   * @return the size
   */
  public Size getSize(String html) {
    el.update(html);
    Size size = el.getSize();
    el.update("");
    return size;
  }

  /**
   * Returns the measured width of the specified text.
   * 
   * @param html the html content to measure
   * @return the width in pixels
   */
  public int getWidth(String html) {
    el.setStyleAttribute("width", "auto");
    return getSize(html).width;
  }

  /**
   * 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.
   * 
   * @param width the width to set on the element
   */
  public void setFixedWidth(int width) {
    el.setWidth(width);
  }

}