/* AccessibleComponent.java -- aids in accessibly rendering Java components
   Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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02111-1307 USA.

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package javax.accessibility;

import java.awt.Color;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.FocusListener;

/**
 * Objects which are to be rendered to a screen as part of a graphical
 * user interface should implement this interface.  Accessibility
 * software can use the implementations of this interface to determine
 * and set the screen representation for an object.
 *
 * <p>The <code>AccessibleContext.getAccessibleComponent()</code> method
 * should return <code>null</code> if an object does not implement this
 * interface.
 *
 * @author Eric Blake <ebb9@email.byu.edu>
 * @see Accessible
 * @see AccessibleContext
 * @see AccessibleContext#getAccessibleComponent()
 * @since 1.2
 * @status updated to 1.4
 */
public interface AccessibleComponent
{
  /**
   * Get the background color of this component.
   *
   * @return the background color of this component, or null if not supported
   * @see #setBackground(Color)
   */
  Color getBackground();

  /**
   * Set the background color of this component to the specified color.
   *
   * @param color the color to set the background to
   * @see #getBackground()
   */
  void setBackground(Color color);

  /**
   * Get the foreground color of this component.
   *
   * @return the foreground color of this component, or null if not supported
   * @see #setForeground(Color)
   */
  Color getForeground();

  /**
   * Set the foreground color of this component.
   *
   * @param color the color to set the foreground to
   * @see #getForeground()
   */
  void setForeground(Color color);

  /**
   * Get the cursor of this component.
   *
   * @return the Cursor of this component, or null if not supported
   * @see #setCursor(Cursor)
   */
  Cursor getCursor();

  /**
   * Set the cursor of the component.
   *
   * @param cursor the graphical representation of the cursor to use
   * @see #getCursor()
   */
  void setCursor(Cursor cursor);

  /**
   * Get the font of this component
   *
   * @return the font of the component, or null if not supported
   * @see setFont(Font)
   */
  Font getFont();

  /**
   * Set the font of this component.
   *
   * @param font the font to use
   * @see #getFont()
   */
  void setFont(Font font);

  /**
   * Get the <code>FontMetrics</code> of the specified font in this component.
   *
   * @param font the specified font
   * @return the metrics for the specified font, or null if not supported
   * @throws NullPointerException if font is null
   * @see #getFont()
   */
  FontMetrics getFontMetrics(Font font);

  /**
   * Indicates whether or not this component is enabled. An object which is
   * enabled also has AccessibleState.ENABLED in its StateSet.
   *
   * @return true if the component is enabled
   * @see #setEnabled(boolean)
   * @see AccessibleContext#getAccessibleStateSet()
   * @see AccessibleState#ENABLED
   */
  boolean isEnabled();

  /**
   * Set this component to an enabled or disabled state.
   *
   * @param b true to enable the component, else disable it
   * @see #isEnabled()
   */
  void setEnabled(boolean b);

  /**
   * Indicates whether or not this component is visible or intends to be
   * visible although one of its ancestors may not be. An object which is
   * visible also has AccessibleState.VISIBLE in its StateSet. Check
   * <code>isShowing()</code> to see if the object is on screen.
   *
   * @return true if the component is visible
   * @see #setVisible(boolean)
   * @see AccessibleContext#getAccessibleStateSet()
   * @see AccessibleState#VISIBLE
   */
  boolean isVisible();

  /**
   * Set the visible state of this component.
   *
   * @param b true to make the component visible, else hide it
   * @see #isVisible()
   */
  void setVisible(boolean b);

  /**
   * Indicates whether or not this component is visible by checking
   * the visibility of this component and its ancestors. The component may
   * be hidden on screen by another component like pop-up help. An object
   * which is showing on screen also has AccessibleState.SHOWING in its
   * StateSet.
   *
   * @return true if component and ancestors are visible
   * @see #isVisible()
   * @see #setVisible(boolean)
   * @see AccessibleContext#getAccessibleStateSet()
   * @see AccessibleState#SHOWING
   */
  boolean isShowing();

  /**
   * Tests whether or not the specified point is contained within
   * this component.  The coordinates are specified relative to this
   * component's coordinate system.
   *
   * @param point the Point to locate
   * @return true if the point is within this component
   * @throws NullPointerException if point is null
   * @see #getBounds()
   */
  boolean contains(Point point);

  /**
   * Get the location of this component in the screen's coordinate space.
   * The point specified is the top-left corner of this component.
   *
   * @return the location on screen, or null if off-screen
   * @see #getBounds()
   * @see #getLocation()
   */
  Point getLocationOnScreen();

  /**
   * Get the location of this component in the parent's coordinate system.
   * The point specified is the top-left corner of this component.
   *
   * @return the location in the parent on screen, or null if off-screen
   * @see #getBounds()
   * @see #getLocationOnScreen()
   * @see #setLocation(Point)
   */
  Point getLocation();

  /**
   * Set the location of this component relative to its parent.  The point
   * specified represents the top-left corner of this component.
   *
   * @param point the top-left corner of this component relative to the parent
   * @throws NullPointerException if point is null
   * @see #getLocation()
   */
  void setLocation(Point point);

  /**
   * Get the bounds of this component relative to its parent - it's width,
   * height, and relative location to its parent.
   *
   * @return the bounds of this component, or null if not on screen
   * @see #contains(Point)
   */
  Rectangle getBounds();

  /**
   * Set the bounds of this component to the specified height and width, and
   * relative location to its parent.
   *
   * @param rectangle the new height, width, and relative location
   * @throws NullPointerException if rectangle is null
   */
  void setBounds(Rectangle rectangle);

  /**
   * Get the size of this component - it's width and height.
   *
   * @return the dimensions of this component, or null if not on screen
   * @see #setSize(Dimension)
   */
  Dimension getSize();

  /**
   * Set the size of this component to the given dimensions.
   *
   * @param dimension the new size of the component
   * @throws NullPointerException if dimension is null
   * @see #getSize()
   */
  void setSize(Dimension dimension);

  /**
   * If an object exists at the specified point which is a child of this
   * parent component, and it is accessible, then it is returned.
   *
   * @param point the location within this component's coordinate system
   * @return the accessible child object at that point, or null
   */
  Accessible getAccessibleAt(Point point);

  /**
   * Indicates whether or not this component can accept focus. An object
   * which can accept focus also has AccessibleState.FOCUSABLE in its
   * StateSet.
   *
   * @return true if the component can accept focus
   * @see AccessibleContext#getAccessibleStateSet()
   * @see AccessibleState#FOCUSABLE
   * @see AccessibleState#FOCUSED
   */
  boolean isFocusTraversable();

  /**
   * If this method is called this component will attempt to gain focus,
   * but if it cannot accept focus nothing happens. On success, the StateSet
   * will contain AccessibleState.FOCUSED
   *
   * @see #isFocusTraversable()
   * @see AccessibleState#FOCUSED
   */
  void requestFocus();

  /**
   * Adds the specified listener to this component.
   *
   * @param listener the listener to add to this component
   * @see #removeFocusListener(FocusListener)
   */
  void addFocusListener(FocusListener listener);

  /**
   * Removes the specified listener from this component.
   *
   * @param listener the listener to remove
   * @see #addFocusListener(FocusListener)
   */
  void removeFocusListener(FocusListener listener);
} // interface AccessibleComponent