Extended Example

This utility class has methods for :

• centering windows on the screen, or with respect to a parent window
• equalizing sizes of components
• imposing an alignment on all items in a Box
• creating borders of a standard size
• creating dialog titles of a standard format
• retrieving images
• creating pairs of components, both for user input (JLabel and JTextField) and simple display (two JLabel objects)
• using GridBagConstraints in a concise manner
• formatting numbers, times, and percents

package hirondelle.stocks.util.ui;

import hirondelle.stocks.util.Args;
import hirondelle.stocks.util.Consts;
import hirondelle.stocks.util.Util;

import java.util.*;
import java.text.*;
import java.net.URL;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
import javax.swing.plaf.metal.MetalLookAndFeel;
import hirondelle.stocks.preferences.GeneralLookPreferencesEditor;

/** Static convenience methods for GUIs which eliminate code duplication.*/
public final class UiUtil {

  /**
  * <tt>pack</tt>, center, and <tt>show</tt> a window on the screen.
  *
  * <P>If the size of <tt>aWindow</tt> exceeds that of the screen, 
  * then the size of <tt>aWindow</tt> is reset to the size of the screen.
  */
  public static void centerAndShow(Window aWindow){
    //note that the order here is important
    
    aWindow.pack();
    /*
     * If called from outside the event dispatch thread (as is 
     * the case upon startup, in the launch thread), then 
     * in principle this code is not thread-safe: once pack has 
     * been called, the component is realized, and (most) further
     * work on the component should take place in the event-dispatch 
     * thread. 
     *
     * In practice, it is exceedingly unlikely that this will lead 
     * to an error, since invisible components cannot receive events.
     */
    Dimension screen = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension window = aWindow.getSize();
    //ensure that no parts of aWindow will be off-screen
    if (window.height > screen.height) {
      window.height = screen.height;
    }
    if (window.width > screen.width) {
      window.width = screen.width;
    }
    int xCoord = (screen.width/2 - window.width/2);
    int yCoord = (screen.height/2 - window.height/2);
    aWindow.setLocation( xCoord, yCoord );
   
    aWindow.show();
  }
  
  /**
  * A window is packed, centered with respect to a parent, and then shown.
  *
  * <P>This method is intended for dialogs only.
  *
  * <P>If centering with respect to a parent causes any part of the dialog 
  * to be off screen, then the centering is overidden, such that all of the 
  * dialog will always appear fully on screen, but it will still appear 
  * near the parent.
  *
  * @param aWindow must have non-null result for <tt>aWindow.getParent</tt>.
  */
  public static void centerOnParentAndShow(Window aWindow){
    aWindow.pack();
    
    Dimension parent = aWindow.getParent().getSize();
    Dimension window = aWindow.getSize();
    int xCoord = 
      aWindow.getParent().getLocationOnScreen().x + 
     (parent.width/2 - window.width/2)
    ;
    int yCoord = 
      aWindow.getParent().getLocationOnScreen().y + 
      (parent.height/2 - window.height/2)
    ;
    
    //Ensure that no part of aWindow will be off-screen
    Dimension screen = Toolkit.getDefaultToolkit().getScreenSize();
    int xOffScreenExcess = xCoord + window.width - screen.width;
    if ( xOffScreenExcess > 0 ) {
      xCoord = xCoord - xOffScreenExcess;
    }
    if (xCoord < 0 ) {
      xCoord = 0;
    }
    int yOffScreenExcess = yCoord + window.height - screen.height;
    if ( yOffScreenExcess > 0 ) {
      yCoord = yCoord - yOffScreenExcess;
    }
    if (yCoord < 0) {
      yCoord = 0;
    }
    
    aWindow.setLocation( xCoord, yCoord );
    aWindow.show();
  }

  /**
  * Return a border of dimensions recommended by the Java Look and Feel 
  * Design Guidelines, suitable for many common cases.
  *
  *<P>Each side of the border has size {@link UiConsts#STANDARD_BORDER}.
  */
  public static Border getStandardBorder(){
    return BorderFactory.createEmptyBorder(
      UiConsts.STANDARD_BORDER, 
      UiConsts.STANDARD_BORDER, 
      UiConsts.STANDARD_BORDER, 
      UiConsts.STANDARD_BORDER
    );
  }

  /**
  * Return text which conforms to the Look and Feel Design Guidelines 
  * for the title of a dialog : the application name, a colon, then 
  * the name of the specific dialog.
  *
  *<P>Example return value: <tt>StocksMonitor: Preferences</tt>
  *
  * @param aSpecificDialogName must have visible content
  */
  public static String getDialogTitle(String aSpecificDialogName){
    Args.checkForContent(aSpecificDialogName);
    StringBuilder result = new StringBuilder(Consts.APP_NAME);
    result.append(": ");
    result.append(aSpecificDialogName);
    return result.toString(); 
  }
  
  /**
  * Make a horizontal row of buttons of equal size, whch are equally spaced, 
  * and aligned on the right.
  *
  * <P>The returned component has border spacing only on the top (of the size 
  * recommended by the Look and Feel Design Guidelines).
  * All other spacing must be applied elsewhere ; usually, this will only mean 
  * that the dialog's top-level panel should use {@link #getStandardBorder}.
  * 
  * @param aButtons contains the buttons to be placed in a row.
  */
  public static JComponent getCommandRow(java.util.List<JComponent> aButtons){
    equalizeSizes( aButtons );
    JPanel panel = new JPanel();
    LayoutManager layout = new BoxLayout(panel, BoxLayout.X_AXIS);
    panel.setLayout( layout );
    panel.setBorder(  BorderFactory.createEmptyBorder(UiConsts.THREE_SPACES, 0, 0, 0) );
    panel.add( Box.createHorizontalGlue() );
    Iterator<JComponent> buttonsIter = aButtons.iterator();
    while ( buttonsIter.hasNext() ) {
      panel.add( buttonsIter.next() );
      if ( buttonsIter.hasNext() ) {
        panel.add( Box.createHorizontalStrut(UiConsts.ONE_SPACE) );
      }
    }
    return panel;
  }
  
  /**
  * Make a vertical row of buttons of equal size, whch are equally spaced, 
  * and aligned on the right.
  *
  * <P>The returned component has border spacing only on the left (of the size 
  * recommended by the Look and Feel Design Guidelines).
  * All other spacing must be applied elsewhere ; usually, this will only mean 
  * that the dialog's top-level panel should use {@link #getStandardBorder}.
  * 
  * @param aButtons contains the buttons to be placed in a column
  */
  public static JComponent getCommandColumn( java.util.List<JComponent> aButtons ){
    equalizeSizes( aButtons );
    JPanel panel = new JPanel();
    LayoutManager layout = new BoxLayout(panel, BoxLayout.Y_AXIS);
    panel.setLayout( layout );
    panel.setBorder(
      BorderFactory.createEmptyBorder(0,UiConsts.THREE_SPACES, 0,0)
    );
    //(no for-each is used here, because of the 'not-yet-last' check)
    Iterator<JComponent> buttonsIter = aButtons.iterator();
    while ( buttonsIter.hasNext() ) {
      panel.add(buttonsIter.next());
      if ( buttonsIter.hasNext() ) {
        panel.add( Box.createVerticalStrut(UiConsts.ONE_SPACE) );
      }
    }
    panel.add( Box.createVerticalGlue() );
    return panel;
  }

  /**
  * Return an <tt>ImageIcon</tt> using its <tt>String</tt> identifier.
  *
  * @param aImageId starts with '/', and refers to an image resource 
  * which is accessible through {@link Class#getResource}.
  */
  public static ImageIcon getImageIcon(String aImageId){
    if( ! aImageId.startsWith(BACK_SLASH) ){
      throw new IllegalArgumentException(
        "Image identifier does not start with backslash: " + aImageId
      );
    }
    return fetchImageIcon(aImageId, UiUtil.class);
  }

  /**
  * Return an <tt>ImageIcon</tt> using its <tt>String</tt> identifier, relative to 
  * a given class.
  *
  * @param aImageId does NOT start with '/', and must refer to an image resource which is 
  * accessible through {@link Class#getResource}.
  * @param aClass the class relative to which the image is located.
  */
  public static ImageIcon getImageIcon(String aImageId, Class<?> aClass){
    if( aImageId.startsWith(BACK_SLASH) ){
      throw new IllegalArgumentException(
        "Image identifier starts with a backslash: " + aImageId
      );
    }
    return fetchImageIcon(aImageId, aClass);
  }
  
  /**
  * Return a square icon which paints nothing, and whose dimensions correspond 
  * to the user preference for icon size.
  *
  * <P>A common problem occurs with text alignment in menus, where there is 
  * a mixture of menu items with and without an icon. Adding an empty icon 
  * to menu items which do not have one will adjust its alignment to match 
  * that of the others which do have an icon.
  */
  public static Icon getEmptyIcon(){
    GeneralLookPreferencesEditor prefs = new GeneralLookPreferencesEditor();
    return prefs.hasLargeIcons() ? EmptyIcon.SIZE_24 : EmptyIcon.SIZE_16;
  }
  
  /**
  * Return a <tt>Dimension</tt> whose size is defined not in terms of pixels, 
  * but in terms of a given percent of the screen's width and height. 
  *
  *<P> Use to set the preferred size of a component to a certain 
  * percentage of the screen.  
  *
  * @param aPercentWidth percentage width of the screen, in range <tt>1..100</tt>.
  * @param aPercentHeight percentage height of the screen, in range <tt>1..100</tt>.
  */
  public static final Dimension getDimensionFromPercent(
    int aPercentWidth, int aPercentHeight
   ){
    int low = 1;
    int high = 100;
    Args.checkForRange(aPercentWidth, low, high);
    Args.checkForRange(aPercentHeight, low, high);
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    return calcDimensionFromPercent(screenSize, aPercentWidth, aPercentHeight);
  }

  /**
   * Sets the items in <tt>aComponents</tt> to the same size.
   *
   * <P>Sets each component's preferred and maximum sizes. 
   * The actual size is determined by the layout manager, whcih adjusts 
   * for locale-specific strings and customized fonts. (See this 
   * <a href="http://java.sun.com/products/jlf/ed2/samcode/prefere.html">Sun doc</a> 
   * for more information.)
   *
   * @param aComponents items whose sizes are to be equalized
   */
  public static void equalizeSizes(java.util.List<JComponent> aComponents) {
    Dimension targetSize = new Dimension(0,0);
    for(JComponent comp: aComponents ) {
      Dimension compSize = comp.getPreferredSize();
      double width = Math.max(targetSize.getWidth(), compSize.getWidth());
      double height = Math.max(targetSize.getHeight(), compSize.getHeight());
      targetSize.setSize(width, height);
    }
    setSizes(aComponents, targetSize);
  }
  
  /**
  * Create a pair of components, a <tt>JLabel</tt> and an associated 
  * <tt>JTextField</tt>, as is typically used for user input.
  *
  *<P>The <tt>JLabel</tt> appears on the left, and the <tt>JTextField</tt>
  * appears on the same  row, just to the right of the <tt>JLabel</tt>. 
  * The <tt>JLabel</tt> has a mnemonic which forwards focus to the 
  * <tt>JTextField</tt> when activated.
  * 
  * @param aContainer holds the pair of components.
  * @param aName text of the <tt>JLabel</tt> component.
  * @param aInitialValue possibly-null initial value to appear 
  * in the <tt>JTextField</tt>; if <tt>null</tt>, then 
  * <tt>JTextField</tt> will be blank.
  * @param aMnemonic <tt>KeyEvent</tt> field, used as the mnemonic for 
  * the <tt>JLabel</tt>.
  * @param aConstraints applied to the <tt>JLabel</tt>; the corresponding 
  * constraints for the <tt>JTextField</tt> are the same as 
  * <tt>aConstraints</tt>, except for <tt>gridx</tt> being incremented by one; 
  * in addition, if <tt>aConstraints</tt> has <tt>weightx=0</tt> (the default),
  * then the entry field will receive <tt>weightx=1.0</tt> (entry field gets more 
  * horizontal space upon resize).
  * @param aTooltip possibly-null text displayed as tool tip for the 
  * <tt>JTextField</tt> ; if <tt>null</tt>, the tool tip is turned off.
  * @return the user input <tt>JTextField</tt>.
  */
  public static JTextField addSimpleEntryField(
    Container aContainer, 
    String aName, 
    String aInitialValue, 
    int aMnemonic, 
    GridBagConstraints aConstraints,
    String aTooltip
  ){
    Args.checkForNull(aName);
    
    JLabel label = new JLabel(aName);
    label.setDisplayedMnemonic(aMnemonic);
    aContainer.add( label, aConstraints );

    JTextField result = new JTextField(UiConsts.SIMPLE_FIELD_WIDTH);
    label.setLabelFor(result);
    result.setToolTipText(aTooltip);
    if (aInitialValue != null) {
      result.setText(aInitialValue);
    }
    aConstraints.gridx = ++aConstraints.gridx;
    if (aConstraints.weightx == 0.0){
      aConstraints.weightx = 1.0;
    }
    aContainer.add(result, aConstraints);
    return result;
  }

  /**
  * Return a set of constraints with convenient default values.
  *
  *<P>Return constraints with these values :
  *<ul>
  * <li> <tt>gridx, gridy</tt> - set to <tt>aX, aY</tt>
  * <li> <tt>anchor - GridBagConstraints.WEST</tt>
  * <li> <tt>insets - Insets(0,0,0, UiConsts.ONE_SPACE)</tt>
  *</ul>
  * 
  *<P> All other items simply take their default values :
  *<ul>
  * <li> <tt>fill - GridBagConstraints.NONE</tt>
  * <li> <tt>gridwidth, gridheight - 0, 0</tt> 
  * <li> <tt>weightx , weighty - 0, 0</tt>
  * <li> <tt>ipadx, ipady - 0, 0</tt>
  *</ul>
  *
  * <P>The caller is free to change the returned constraints, to customize for 
  * their particular needs.
  *
  * @param aY in range <tt>0..10</tt>.
  * @param aX in range <tt>0..10</tt>.
  */
  public static GridBagConstraints getConstraints(int aY, int aX){
    int low = 0;
    int high = 10;
    Args.checkForRange(aY, low, high);
    Args.checkForRange(aX, low, high);
    GridBagConstraints result = new GridBagConstraints();
    result.gridy = aY;
    result.gridx = aX;
    result.anchor = GridBagConstraints.WEST;
    result.insets = new Insets(0,0,0,UiConsts.ONE_SPACE);
    return result;
  }

  /**
  * Return {@link #getConstraints(int, int)}, with the addition of setting 
  * <tt>gridwidth</tt> to <tt>aWidth</tt>, and setting 
  * <tt>gridheight</tt> to <tt>aHeight</tt>.
  *
  * <P>The caller is free to change the returned constraints, to customize for
  * their particular needs.
  *
  * @param aY in range <tt>0..10</tt>.
  * @param aX in range <tt>0..10</tt>.
  * @param aWidth in range <tt>1..10</tt>.
  * @param aHeight in range <tt>1..10</tt>.
  */
  public static GridBagConstraints getConstraints(int aY, int aX, int aWidth, int aHeight){
    int low = 0;
    int high = 10;
    Args.checkForRange(aHeight, low, high);
    Args.checkForRange(aWidth, low, high);
    GridBagConstraints result = getConstraints(aY, aX);
    result.gridheight = aHeight;
    result.gridwidth = aWidth;
    return result;
  }
  
  /**
  * Create a pair of <tt>JLabel</tt> components, as is typically needed 
  * for display of a name-value pair.
  *
  * <P>The name appears on the left, and the value appears on the right, 
  * all on the same row. A colon and an empty space are appended to the name. 
  * 
  * <P> If the the length of "value" label is greater than 
  * {@link UiConsts#MAX_LABEL_LENGTH}, then the text is truncated, an ellipsis
  * is placed at its end, and the full text is placed in a tooltip.
  * 
  * @param aContainer holds the pair of components.
  * @param aName text of the name <tt>JLabel</tt>.
  * @param aValue possibly-null ; if null, then an empty <tt>String</tt>
  * is used for the value; otherwise <tt>Object.toString</tt> is used.
  * @param aConstraints for the name <tt>JLabel</tt>; the corresponding 
  * constraints for the value <tt>JLabel</tt> are mostly taken from 
  * <tt>aConstraints</tt>, except for <tt>gridx</tt> being incremented by one
  * (<tt>weightx</tt> may differ as well - see <tt>aWeightOnDisplay</tt>.)
  * @param aWeightOnDisplay if true, then set <tt>weightx</tt> for the value 
  * field to 1.0 (to give it more horizontal space upon resize).
  * @return the <tt>JLabel</tt> for the value (which is usually variable).
  */
  public static JLabel addSimpleDisplayField(
    Container aContainer, 
    String aName, 
    Object aValue, 
    GridBagConstraints aConstraints,
    boolean aWeightOnDisplay
  ){
    StringBuilder formattedName = new StringBuilder(aName);
    formattedName.append(": ");
    JLabel name = new JLabel( formattedName.toString() );
    aContainer.add( name, aConstraints );
    
    String valueText = (aValue != null? aValue.toString() : Consts.EMPTY_STRING);
    JLabel value = new JLabel(valueText);
    truncateLabelIfLong(value);
    aConstraints.gridx = ++aConstraints.gridx;
    if (aWeightOnDisplay){
      aConstraints.weightx = 1.0;
    }
    aContainer.add( value, aConstraints );
    
    return value;
  }
  
  /**
  * Present a number of read-only items to the user as a vertical listing 
  * of <tt>JLabel</tt> name-value pairs.
  *
  * <P>Each pair is added in the style of 
  * {@link #addSimpleDisplayField} (its <tt>aConstraints</tt> param are those 
  * returned by {@link #getConstraints(int, int)}, and its <tt>aWeightOnDisplay</tt> 
  * param is set to <tt>true</tt>).
  *
  * <P>The order of presentation is determined by the iteration order of 
  * <tt>aNameValuePairs</tt>.
  *
  *<P>The number of items which should be presented using this method is limited, since
  * no scrolling mechanism is given to the user.
  *
  * @param aContainer holds the display fields.
  * @param aNameValuePairs has <tt>String</tt> keys for the names, 
  * and values are possibly null <tt>Object</tt>s; 
  * if null, then an empty <tt>String</tt> is displayed, otherwise
  * <tt>Object.toString</tt> is called on the value and displayed.
  */
  public static void addSimpleDisplayFields(
    Container aContainer, Map<String, String> aNameValuePairs
  ) {
    Set<String> keys = aNameValuePairs.keySet();
    int rowIdx = 0;
    for(String name: keys) {
      String value = aNameValuePairs.get(name);
      if(value == null){
        value = Consts.EMPTY_STRING;
      }
      UiUtil.addSimpleDisplayField(
        aContainer, 
        name, 
        value, 
        UiUtil.getConstraints(rowIdx,0),
        true
      );
      ++rowIdx;
    }
  }
 
  /**
  * Adds "glue" (an empty component with desired resizing behavior) to the bottom 
  * row of a <tt>GridBagLayout</tt> of components. When resized, this glue will 
  * take up extra vertical space.
  *
  * <P>This method is especially useful for text data presented in a listing or 
  * tabular form. Such components naturally resize horizontally, while their vertical 
  * resizing should often be absent. If such a listing is resized vertically, then this 
  * glue can take up the remaining vertical space, keeping the text at the top.
  *
  * @param aPanel uses <tt>GridBagLayout</tt>, and contains components whose 
  * <tt>weighty</tt> values are all 0.0 (the default).
  * @param aLastRowIdx index of the last row of components, in which the glue will be
  * placed.
  */
  public static void addVerticalGridGlue(JPanel aPanel, int aLastRowIdx) {   
    GridBagConstraints glueConstraints = UiUtil.getConstraints(aLastRowIdx,0);
    glueConstraints.weighty = 1.0;
    glueConstraints.fill = GridBagConstraints.VERTICAL;
    aPanel.add( new JLabel(), glueConstraints );
  }
  
  /**
  * Return a <tt>String</tt>, suitable for presentation to the end user, 
  * representing a percentage having two decimal places, using the default locale.
  *
  * <P>An example return value is "5.15%". The intent of this method is to 
  * provide a standard representation and number of decimals for the entire 
  * application. If a different number of decimal places is required, then 
  * the caller should use <tt>NumberFormat</tt> instead.
  */
  public static String getLocalizedPercent( Number aNumber ){
    NumberFormat localFormatter = NumberFormat.getPercentInstance();
    localFormatter.setMinimumFractionDigits(2);
    return localFormatter.format( aNumber.doubleValue() );
  }
  
  /**
  * Return a <tt>String</tt>, suitable for presentation to the end user, 
  * representing an integral number with no decimal places, using the default 
  * locale.
  *
  * <P>An example return value is "8,000". The intent of this method is to 
  * provide a standard representation of integers for the entire 
  * application.
  */
  public static String getLocalizedInteger( Number aNumber ) {
    NumberFormat localFormatter = NumberFormat.getNumberInstance();
    return localFormatter.format( aNumber.intValue() );
  }

  /**
  * Return a <tt>String</tt>, suitable for presentation to the end user, 
  * representing a date in <tt>DateFormat.SHORT</tt> and the default locale.
  */
  public static String getLocalizedTime(Date aDate){
    DateFormat dateFormat = DateFormat.getTimeInstance(DateFormat.SHORT);
    return dateFormat.format(aDate);
  }

  /**
  * Make the sytem emit a beep.
  *
  * <P>May not beep unless the speakers are turned on, so this cannot 
  * be guaranteed to work.
  */
  public static void beep(){
    Toolkit.getDefaultToolkit().beep();
  }

  /**
  * An alternative to multi-line labels, for the presentation of 
  * several lines of text, and for which the line breaks are determined 
  * solely by the widget.
  *
  * @param aText must have visible content, doesn't contain newline characters or html.
  * @return <tt>JTextArea</tt> which is not editable, has improved spacing over the 
  * supplied default (placing {@link UiConsts#ONE_SPACE} on the left and right), 
  * which wraps lines on word boundaries, and whose background color is the 
  * same as {@link javax.swing.plaf.metal.MetalLookAndFeel#getMenuBackground}.
  */
  public static JTextArea getStandardTextArea(String aText){
    Args.checkForContent(aText);
    if ( aText.indexOf(Consts.NEW_LINE) != -1 ){
      throw new IllegalArgumentException("Must not contain new line characters: " + aText);
    }
    JTextArea result = new JTextArea(aText);
    result.setEditable(false);
    result.setWrapStyleWord(true);
    result.setLineWrap(true);
    result.setMargin( new Insets(0,UiConsts.ONE_SPACE,0,UiConsts.ONE_SPACE) );
    //this is a bit hacky: the desired color is "secondary3", but cannot see how 
    //to reference it directly; hence, an element which uses secondary3 is used instead.
    result.setBackground( MetalLookAndFeel.getMenuBackground() ); 
    
    return result;
  }
  
  /**
  * An alternative to multi-line labels, for the presentation of 
  * several lines of text, and for which line breaks are determined 
  * solely by <tt>aText</tt>, and not by the widget.
  *
  * @param aText has visible content
  * @return <tt>JTextArea</tt> which is not editable, has improved spacing over the 
  * supplied default (placing {@link UiConsts#ONE_SPACE} on the left and right), 
  * and whose background color is the same as 
  * {@link javax.swing.plaf.metal.MetalLookAndFeel#getMenuBackground}.
  */
  public static JTextArea getStandardTextAreaHardNewLines(String aText){
    Args.checkForContent(aText);
    JTextArea result = new JTextArea(aText);
    result.setEditable(false);
    result.setMargin( new Insets(0,UiConsts.ONE_SPACE,0,UiConsts.ONE_SPACE) );
    result.setBackground( MetalLookAndFeel.getMenuBackground() ); 
    return result;
  }
  
  /**
  * Imposes a uniform horizontal alignment on all items in a container.
  *
  *<P> Intended especially for <tt>BoxLayout</tt>, where all components need 
  * to share the same alignment in order for display to be reasonable. 
  * (Indeed, this method may only work for <tt>BoxLayout</tt>, since apparently 
  * it is the only layout to use <tt>setAlignmentX, setAlignmentY</tt>.)
  *
  * @param aContainer contains only <tt>JComponent</tt> objects.
  */
  public static void alignAllX(Container aContainer, UiUtil.AlignX aAlignment){
    java.util.List<Component> components = Arrays.asList( aContainer.getComponents() );
    for(Component comp: components){
      JComponent jcomp = (JComponent)comp;
      jcomp.setAlignmentX( aAlignment.getValue() );
    }
  }
  
  /** Enumeration for horizontal alignment. */
  public enum AlignX {
    LEFT(Component.LEFT_ALIGNMENT),
    CENTER(Component.CENTER_ALIGNMENT),
    RIGHT(Component.RIGHT_ALIGNMENT);
    public float getValue(){
      return fValue;
    }
    private final float fValue;
    private AlignX(float aValue){
      fValue = aValue;
    }
  }
  
  /**
  * Imposes a uniform vertical alignment on all items in a container.
  *
  *<P> Intended especially for <tt>BoxLayout</tt>, where all components need 
  * to share the same alignment in order for display to be reasonable.
  * (Indeed, this method may only work for <tt>BoxLayout</tt>, since apparently 
  * it is the only layout to use <tt>setAlignmentX, setAlignmentY</tt>.)
  *
  * @param aContainer contains only <tt>JComponent</tt> objects.
  */
  public static void alignAllY(Container aContainer, UiUtil.AlignY aAlignment){
    java.util.List components = Arrays.asList( aContainer.getComponents() );
    Iterator compsIter = components.iterator();
    while ( compsIter.hasNext() ) {
      JComponent comp = (JComponent)compsIter.next();
      comp.setAlignmentY( aAlignment.getValue() );
    }
  }

  /** Type-safe enumeration vertical alignment. */
  public enum AlignY {
    TOP(Component.TOP_ALIGNMENT),
    CENTER(Component.CENTER_ALIGNMENT),
    BOTTOM(Component.BOTTOM_ALIGNMENT);
    float getValue(){
      return fValue;
    }
    private final float fValue;
    private AlignY( float aValue){
      fValue = aValue;
    }
  }
  
  /**
  * Ensure that <tt>aRootPane</tt> has no default button associated with it.
  *
  * <P>Intended mainly for dialogs where the user is confirming a delete action.
  * In this case, an explicit Yes or No is preferred, with no default action being 
  * taken when the user hits the Enter key. 
  */
  public static void noDefaultButton(JRootPane aRootPane){
    aRootPane.setDefaultButton(null);
  }

  // PRIVATE //
  
  private static final String BACK_SLASH = "/";

  /**
  * If <tt>aIconName</tt> indicates that the icon is part of the standard graphic
  * repository (by starting with "/toolbar"), then append either "16.gif" or 
  * "24.gif" to the name, according to the user's current preference for icon size.
  */
  private static String addSizeToStandardIcon(String aIconName){
    assert( Util.textHasContent(aIconName) );
    StringBuilder result = new StringBuilder(aIconName);
    if ( aIconName.startsWith("/toolbar") ) {
      GeneralLookPreferencesEditor prefs = new GeneralLookPreferencesEditor();
      if ( prefs.hasLargeIcons() ) {
        result.append("24.gif");
      }
      else {
        result.append("16.gif");
      }
    }
    return result.toString();
  }

  private static void setSizes(java.util.List aComponents, Dimension aDimension){
    Iterator compsIter = aComponents.iterator();      
    while ( compsIter.hasNext() ) {
      JComponent comp = (JComponent) compsIter.next();
      comp.setPreferredSize( (Dimension)aDimension.clone() );
      comp.setMaximumSize( (Dimension)aDimension.clone() );
    }
  }

  private static Dimension calcDimensionFromPercent(
    Dimension aSourceDimension, int aPercentWidth, int aPercentHeight
  ){
    int width = aSourceDimension.width * aPercentWidth/100;
    int height = aSourceDimension.height * aPercentHeight/100;
    return new Dimension(width, height);
  }

  /**
  * If aLabel has text which is longer than MAX_LABEL_LENGTH, then truncate 
  * the label text and place an ellipsis at the end; the original text is placed 
  * in a tooltip.
  *
  * This is particularly useful for displaying file names, whose length 
  * can vary widely between deployments.
  */
  private static void truncateLabelIfLong(JLabel aLabel){
    String originalText = aLabel.getText();
    if (originalText.length() > UiConsts.MAX_LABEL_LENGTH){
      aLabel.setToolTipText( originalText );
      String truncatedText = 
        originalText.substring(0, UiConsts.MAX_LABEL_LENGTH) + Consts.ELLIPSIS
      ;
      aLabel.setText(truncatedText);
    }
  }
  
  private static ImageIcon fetchImageIcon(String aImageId, Class<?> aClass){
    String imgLocation = addSizeToStandardIcon(aImageId);
    URL imageURL = aClass.getResource(imgLocation);
    if ( imageURL != null ) {
      return new ImageIcon(imageURL);
    }
    else {
      throw new IllegalArgumentException("Cannot retrieve image using id: " + aImageId);
    }
  }
}