/*
 * Copyright (c) 1995, 2014, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */
package java.awt;

import java.awt.peer.LabelPeer;
import java.io.IOException;
import java.io.ObjectInputStream;
import javax.accessibility.*;

/**
 * A <code>Label</code> object is a component for placing text in a
 * container. A label displays a single line of read-only text.
 * The text can be changed by the application, but a user cannot edit it
 * directly.
 * <p>
 * For example, the code&nbsp;.&nbsp;.&nbsp;.
 *
 * <hr><blockquote><pre>
 * setLayout(new FlowLayout(FlowLayout.CENTER, 10, 10));
 * add(new Label("Hi There!"));
 * add(new Label("Another Label"));
 * </pre></blockquote><hr>
 * <p>
 * produces the following labels:
 * <p>
 * <img src="doc-files/Label-1.gif" alt="Two labels: 'Hi There!' and 'Another label'"
 * style="float:center; margin: 7px 10px;">
 *
 * @author Sami Shaio
 * @since JDK1.0
 */
public class Label extends Component implements Accessible {

 static {
 /* ensure that the necessary native libraries are loaded */
 Toolkit.loadLibraries();
 if (!GraphicsEnvironment.isHeadless()) {
 initIDs();
 }
 }

 /**
 * Indicates that the label should be left justified.
 */
 public static final int LEFT = 0;

 /**
 * Indicates that the label should be centered.
 */
 public static final int CENTER = 1;

 /**
 * Indicates that the label should be right justified.
 * @since JDK1.0t.
 */
 public static final int RIGHT = 2;

 /**
 * The text of this label.
 * This text can be modified by the program
 * but never by the user.
 *
 * @serial
 * @see #getText()
 * @see #setText(String)
 */
 String text;

 /**
 * The label's alignment. The default alignment is set
 * to be left justified.
 *
 * @serial
 * @see #getAlignment()
 * @see #setAlignment(int)
 */
 int alignment = LEFT;

 private static final String base = "label";
 private static int nameCounter = 0;

 /*
 * JDK 1.1 serialVersionUID
 */
 private static final long serialVersionUID = 3094126758329070636L;

 /**
 * Constructs an empty label.
 * The text of the label is the empty string <code>""</code>.
 * @exception HeadlessException if GraphicsEnvironment.isHeadless()
 * returns true.
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 public Label() throws HeadlessException {
 this("", LEFT);
 }

 /**
 * Constructs a new label with the specified string of text,
 * left justified.
 * @param text the string that the label presents.
 * A <code>null</code> value
 * will be accepted without causing a NullPointerException
 * to be thrown.
 * @exception HeadlessException if GraphicsEnvironment.isHeadless()
 * returns true.
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 public Label(String text) throws HeadlessException {
 this(text, LEFT);
 }

 /**
 * Constructs a new label that presents the specified string of
 * text with the specified alignment.
 * Possible values for <code>alignment</code> are <code>Label.LEFT</code>,
 * <code>Label.RIGHT</code>, and <code>Label.CENTER</code>.
 * @param text the string that the label presents.
 * A <code>null</code> value
 * will be accepted without causing a NullPointerException
 * to be thrown.
 * @param alignment the alignment value.
 * @exception HeadlessException if GraphicsEnvironment.isHeadless()
 * returns true.
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 public Label(String text, int alignment) throws HeadlessException {
 GraphicsEnvironment.checkHeadless();
 this.text = text;
 setAlignment(alignment);
 }

 /**
 * Read a label from an object input stream.
 * @exception HeadlessException if
 * <code>GraphicsEnvironment.isHeadless()</code> returns
 * <code>true</code>
 * @serial
 * @since 1.4
 * @see java.awt.GraphicsEnvironment#isHeadless
 */
 private void readObject(ObjectInputStream s)
 throws ClassNotFoundException, IOException, HeadlessException {
 GraphicsEnvironment.checkHeadless();
 s.defaultReadObject();
 }

 /**
 * Construct a name for this component. Called by getName() when the
 * name is <code>null</code>.
 */
 String constructComponentName() {
 synchronized (Label.class) {
 return base + nameCounter++;
 }
 }

 /**
 * Creates the peer for this label. The peer allows us to
 * modify the appearance of the label without changing its
 * functionality.
 */
 public void addNotify() {
 synchronized (getTreeLock()) {
 if (peer == null)
 peer = getToolkit().createLabel(this);
 super.addNotify();
 }
 }

 /**
 * Gets the current alignment of this label. Possible values are
 * <code>Label.LEFT</code>, <code>Label.RIGHT</code>, and
 * <code>Label.CENTER</code>.
 * @see java.awt.Label#setAlignment
 */
 public int getAlignment() {
 return alignment;
 }

 /**
 * Sets the alignment for this label to the specified alignment.
 * Possible values are <code>Label.LEFT</code>,
 * <code>Label.RIGHT</code>, and <code>Label.CENTER</code>.
 * @param alignment the alignment to be set.
 * @exception IllegalArgumentException if an improper value for
 * <code>alignment</code> is given.
 * @see java.awt.Label#getAlignment
 */
 public synchronized void setAlignment(int alignment) {
 switch (alignment) {
 case LEFT:
 case CENTER:
 case RIGHT:
 this.alignment = alignment;
 LabelPeer peer = (LabelPeer)this.peer;
 if (peer != null) {
 peer.setAlignment(alignment);
 }
 return;
 }
 throw new IllegalArgumentException("improper alignment: " + alignment);
 }

 /**
 * Gets the text of this label.
 * @return the text of this label, or <code>null</code> if
 * the text has been set to <code>null</code>.
 * @see java.awt.Label#setText
 */
 public String getText() {
 return text;
 }

 /**
 * Sets the text for this label to the specified text.
 * @param text the text that this label displays. If
 * <code>text</code> is <code>null</code>, it is
 * treated for display purposes like an empty
 * string <code>""</code>.
 * @see java.awt.Label#getText
 */
 public void setText(String text) {
 boolean testvalid = false;
 synchronized (this) {
 if (text != this.text && (this.text == null ||
 !this.text.equals(text))) {
 this.text = text;
 LabelPeer peer = (LabelPeer)this.peer;
 if (peer != null) {
 peer.setText(text);
 }
 testvalid = true;
 }
 }

 // This could change the preferred size of the Component.
 if (testvalid) {
 invalidateIfValid();
 }
 }

 /**
 * Returns a string representing the state of this <code>Label</code>.
 * This method is intended to be used only for debugging purposes, and the
 * content and format of the returned string may vary between
 * implementations. The returned string may be empty but may not be
 * <code>null</code>.
 *
 * @return the parameter string of this label
 */
 protected String paramString() {
 String align = "";
 switch (alignment) {
 case LEFT: align = "left"; break;
 case CENTER: align = "center"; break;
 case RIGHT: align = "right"; break;
 }
 return super.paramString() + ",align=" + align + ",text=" + text;
 }

 /**
 * Initialize JNI field and method IDs
 */
 private static native void initIDs();


/////////////////
// Accessibility support
////////////////


 /**
 * Gets the AccessibleContext associated with this Label.
 * For labels, the AccessibleContext takes the form of an
 * AccessibleAWTLabel.
 * A new AccessibleAWTLabel instance is created if necessary.
 *
 * @return an AccessibleAWTLabel that serves as the
 * AccessibleContext of this Label
 * @since 1.3
 */
 public AccessibleContext getAccessibleContext() {
 if (accessibleContext == null) {
 accessibleContext = new AccessibleAWTLabel();
 }
 return accessibleContext;
 }

 /**
 * This class implements accessibility support for the
 * <code>Label</code> class. It provides an implementation of the
 * Java Accessibility API appropriate to label user-interface elements.
 * @since 1.3
 */
 protected class AccessibleAWTLabel extends AccessibleAWTComponent
 {
 /*
 * JDK 1.3 serialVersionUID
 */
 private static final long serialVersionUID = -3568967560160480438L;

 public AccessibleAWTLabel() {
 super();
 }

 /**
 * Get the accessible name of this object.
 *
 * @return the localized name of the object -- can be null if this
 * object does not have a name
 * @see AccessibleContext#setAccessibleName
 */
 public String getAccessibleName() {
 if (accessibleName != null) {
 return accessibleName;
 } else {
 if (getText() == null) {
 return super.getAccessibleName();
 } else {
 return getText();
 }
 }
 }

 /**
 * Get the role of this object.
 *
 * @return an instance of AccessibleRole describing the role of the object
 * @see AccessibleRole
 */
 public AccessibleRole getAccessibleRole() {
 return AccessibleRole.LABEL;
 }

 } // inner class AccessibleAWTLabel

}