swing/border/EtchedBorder.java

/* EtchedBorder.java --
   Copyright (C) 2003 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
the Free Software Foundation; either version 2, or (at your option)
any later version.

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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
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package javax.swing.border;

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;


/**
 * A border that looks like an engraving etched into the background
 * surface, or (in its raised variant) coming out of the surface
 * plane. Using different constructors, it is possible to either
 * explicitly specify the border colors, or to let the colors derive
 * from the background color of the enclosed Component.
 *
 * <p><img src="doc-files/EtchedBorder-1.png" width="500" height="200"
 * alt="[An illustration of the two EtchedBorder variants]" />
 *
 * @author Sascha Brawer (brawer@dandelis.ch)
 */
public class EtchedBorder extends AbstractBorder
{
  /**
   * Determined using the <code>serialver</code> tool
   * of Apple/Sun JDK 1.3.1 on MacOS X 10.1.5.
   */
  static final long serialVersionUID = 4001244046866360638L;


  /**
   * Indicates that the border appears as coming out of the
   * background.
   */
  public static final int RAISED = 0;


  /**
   * Indicates that the border appears as engraved into the
   * background.
   */
  public static final int LOWERED = 1;


  /**
   * The type of this EtchedBorder, which is either {@link #RAISED}
   * or {@link #LOWERED}.
   */
  protected int etchType;


  /**
   * The highlight color, or <code>null</code> to indicate that the
   * color shall be derived from the background of the enclosed
   * component.
   */
  protected Color highlight;


  /**
   * The shadow color, or <code>null</code> to indicate that the
   * color shall be derived from the background of the enclosed
   * component.
   */
  protected Color shadow;


  /**
   * Constructs a lowered EtchedBorder. The colors will be derived
   * from the background color of the enclosed Component when the
   * border gets painted.
   */
  public EtchedBorder()
  {
    this(LOWERED);
  }


  /**
   * Constructs an EtchedBorder with the specified appearance. The
   * colors will be derived from the background color of the enclosed
   * Component when the border gets painted.
   *
   * <p><img src="doc-files/EtchedBorder-1.png" width="500" height="200"
   * alt="[An illustration of the two EtchedBorder variants]" />
   *
   * @param etchType the desired appearance of the border. The value
   *        must be either {@link #RAISED} or {@link #LOWERED}.
   *
   * @throws IllegalArgumentException if <code>etchType</code> has
   *         an unsupported value.
   */
  public EtchedBorder(int etchType)
  {
    if ((etchType != RAISED) && (etchType != LOWERED))
      throw new IllegalArgumentException();

    this.etchType = etchType;

    /* The highlight and shadow fields already have a null value
     * when the constructor gets called, so there is no need to
     * assign a value here.
     */
  }


  /**
   * Constructs a lowered EtchedBorder, explicitly selecting the
   * colors that will be used for highlight and shadow.
   *
   * @param highlight the color that will be used for painting
   *        the highlight part of the border.
   *
   * @param shadow the color that will be used for painting
   *        the shadow part of the border.
   *
   * @see #EtchedBorder(int, Color, Color)
   */
  public EtchedBorder(Color highlight, Color shadow)
  {
    this(LOWERED, highlight, shadow);
  }


  /**
   * Constructs an EtchedBorder with the specified appearance,
   * explicitly selecting the colors that will be used for
   * highlight and shadow.
   *
   * <p><img src="doc-files/EtchedBorder-2.png" width="500" height="200"
   * alt="[An illustration that shows which pixels get painted
   * in what color]" />
   *
   * @param etchType the desired appearance of the border. The value
   *        must be either {@link #RAISED} or {@link #LOWERED}.
   *
   * @param highlight the color that will be used for painting
   *        the highlight part of the border.
   *
   * @param shadow the color that will be used for painting
   *        the shadow part of the border.
   *
   * @throws IllegalArgumentException if <code>etchType</code> has
   *         an unsupported value.
   */
  public EtchedBorder(int etchType, Color highlight, Color shadow)
  {
    this(etchType);  // Checks the validity of the value.
    this.highlight = highlight;
    this.shadow = shadow;
  }


  /**
   * Paints the border for a given component.
   *
   * @param c the component whose border is to be painted.
   * @param g the graphics for painting.
   * @param x the horizontal position for painting the border.
   * @param y the vertical position for painting the border.
   * @param width the width of the available area for painting the border.
   * @param height the height of the available area for painting the border.
   */
  public void paintBorder(Component c, Graphics  g, int x, int y, int width,
                          int height)
  {
    switch (etchType)
    {
    case RAISED:
      paintEtchedBorder(g, x, y, width, height,
                        getHighlightColor(c), getShadowColor(c));
      break;

    case LOWERED:
      paintEtchedBorder(g, x, y, width, height,
                        getShadowColor(c), getHighlightColor(c));
      break;
    }
  }


  /**
   * Measures the width of this border.
   *
   * @param c the component whose border is to be measured.
   *
   * @return an Insets object whose <code>left</code>, <code>right</code>,
   *         <code>top</code> and <code>bottom</code> fields indicate the
   *         width of the border at the respective edge.
   *
   * @see #getBorderInsets(java.awt.Component, java.awt.Insets)
   */
  public Insets getBorderInsets(Component c)
  {
    return new Insets(2, 2, 2, 2);
  }


  /**
   * Measures the width of this border, storing the results into a
   * pre-existing Insets object.
   *
   * @param insets an Insets object for holding the result values.
   *        After invoking this method, the <code>left</code>,
   *        <code>right</code>, <code>top</code> and
   *        <code>bottom</code> fields indicate the width of the
   *        border at the respective edge.
   *
   * @return the same object that was passed for <code>insets</code>.
   *
   * @see #getBorderInsets(Component)
   */
  public Insets getBorderInsets(Component c, Insets insets)
  {
    insets.left = insets.right = insets.top = insets.bottom = 2;
    return insets;
  }


  /**
   * Determines whether this border fills every pixel in its area
   * when painting.
   *
   * <p>If the border colors are derived from the background color of
   * the enclosed component, the result is <code>true</code> because
   * the derivation method always returns opaque colors. Otherwise,
   * the result depends on the opacity of the individual colors.
   *
   * @return <code>true</code> if the border is fully opaque, or
   *         <code>false</code> if some pixels of the background
   *         can shine through the border.
   */
  public boolean isBorderOpaque()
  {
    // If the colors are to be derived from the enclosed Component's
    // background color, the border is guaranteed to be fully opaque
    // because Color.brighten() and Color.darken() always return an
    // opaque color.
    return
      ((highlight == null) || (highlight.getAlpha() == 255))
      && ((shadow == null) || (shadow.getAlpha() == 255));
  }

  /**
   * Returns the appearance of this EtchedBorder, which is either
   * {@link #RAISED} or {@link #LOWERED}.
   */
  public int getEtchType()
  {
    return etchType;
  }


  /**
   * Determines the color that will be used for highlighted parts when
   * painting the border around a given component. If a highlight
   * color has been specified upon constructing the border, that color
   * is returned. Otherwise, the background color of the enclosed
   * component is brightened.
   *
   * @param c the component enclosed by this border.
   *
   * @see java.awt.Component#getBackground()
   * @see java.awt.Color#brighter()
   */
  public Color getHighlightColor(Component c)
  {
    if (highlight != null)
      return highlight;
    else
      return c.getBackground().brighter();
  }

  /**
   * Returns the color that will be used for highlighted parts when
   * painting the border, or <code>null</code> if that color will be
   * derived from the background of the enclosed Component.
   */
  public Color getHighlightColor()
  {
    return highlight;
  }


  /**
   * Determines the color that will be used for shadowed parts when
   * painting the border around a given component. If a shadow color
   * has been specified upon constructing the border, that color is
   * returned. Otherwise, the background color of the enclosed
   * component is darkened.
   *
   * @param c the component enclosed by this border.
   *
   * @see java.awt.Component#getBackground()
   * @see java.awt.Color#darker()
   */
  public Color getShadowColor(Component c)
  {
    if (shadow != null)
      return shadow;
    else
      return c.getBackground().darker();
  }


  /**
   * Returns the color that will be used for shadowed parts when
   * painting the border, or <code>null</code> if that color will be
   * derived from the background of the enclosed Component.
   */
  public Color getShadowColor()
  {
    return shadow;
  }


  /**
   * Paints a two-pixel etching in two colors.
   *
   * <pre>
   * +++++++++++.
   * +.........+.    + = color a
   * +.        +.    . = color b
   * +.        +.
   * +++++++++++.
   * ............</pre>
   *
   * @param g the graphics for painting.
   * @param x the horizontal position for painting the border.
   * @param y the vertical position for painting the border.
   * @param width the width of the available area for painting the border.
   * @param height the height of the available area for painting the border.
   * @param a one of the two colors.
   * @param b the second of the two colors.
   */
  private static void paintEtchedBorder(Graphics g, int x, int y, int width,
                                        int height, Color a, Color b)
  {
    Color oldColor;

    oldColor = g.getColor();
    g.translate(x, y);
    width = width - 1;
    height = height - 1;

    try
    {
      // To understand this code, it might be helpful to look at the
      // images that are included with the JavaDoc. They are located
      // in the "doc-files" subdirectory. EtchedBorder-2.png might
      // be especially informative.
      g.setColor(a);
      g.drawRect(0, 0, width - 1, height - 1);

      g.setColor(b);
      g.drawLine(1, 1, width - 2, 1);            // top edge
      g.drawLine(1, 2, 1, height - 2);           // left edge
      g.drawLine(0, height, width, height);      // bottom edge
      g.drawLine(width, 0, width, height - 1);   // right edge
    }
    finally
    {
      g.translate(-x, -y);
      g.setColor(oldColor);
    }
  }
}