graphicattribute.java

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/*
 * @(#)GraphicAttribute.java	1.17 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/*
 * (C) Copyright Taligent, Inc. 1996 - 1997, All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - 1998, All Rights Reserved
 *
 * The original version of this source code and documentation is
 * copyrighted and owned by Taligent, Inc., a wholly-owned subsidiary
 * of IBM. These materials are provided under terms of a License
 * Agreement between Taligent and Sun. This technology is protected
 * by multiple US and International patents.
 *
 * This notice and attribution to Taligent may not be removed.
 * Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.awt.font;

import java.awt.geom.Rectangle2D;
import java.awt.Graphics2D;
import java.awt.Font;

/**
 * This class is used with the CHAR_REPLACEMENT attribute.
 * <p>
 * The <code>GraphicAttribute</code> class represents a graphic embedded
 * in text. Clients subclass this class to implement their own char
 * replacement graphics.  Clients wishing to embed shapes and images in
 * text need not subclass this class.  Instead, clients can use the
 * {@link ShapeGraphicAttribute} and {@link ImageGraphicAttribute} 
 * classes.
 * <p>
 * Subclasses must ensure that their objects are immutable once they
 * are constructed.  Mutating a <code>GraphicAttribute</code> that
 * is used in a {@link TextLayout} results in undefined behavior from the
 * <code>TextLayout</code>.
 */
public abstract class GraphicAttribute {

    private int fAlignment;

    /** 
     * Aligns top of graphic to top of line. 
     */
    public static final int TOP_ALIGNMENT = -1;

    /** 
     * Aligns bottom of graphic to bottom of line. 
     */
    public static final int BOTTOM_ALIGNMENT = -2;

    /** 
     * Aligns origin of graphic to roman baseline of line. 
     */
    public static final int ROMAN_BASELINE = Font.ROMAN_BASELINE;

    /** 
     * Aligns origin of graphic to center baseline of line. 
     */
    public static final int CENTER_BASELINE = Font.CENTER_BASELINE;

    /** 
     * Aligns origin of graphic to hanging baseline of line. 
     */
    public static final int HANGING_BASELINE = Font.HANGING_BASELINE;

    /**
     * Constructs a <code>GraphicAttribute</code>.
     * Subclasses use this to define the alignment of the graphic.
     * @param alignment an int representing one of the 
     * <code>GraphicAttribute</code> alignment fields
     */
    protected GraphicAttribute(int alignment) {
        if (alignment < BOTTOM_ALIGNMENT || alignment > HANGING_BASELINE) {
	  throw new IllegalArgumentException("bad alignment");
        }
        fAlignment = alignment;
    }

    /**
     * Returns the ascent of this <code>GraphicAttribute</code>.  A
     * graphic can be rendered above its ascent.
     * @return the ascent of this <code>GraphicAttribute</code>.
     * @see #getBounds()
     */
    public abstract float getAscent();

    /**
     * Returns the descent of this <code>GraphicAttribute</code>.  A
     * graphic can be rendered below its descent.
     * @return the descent of this <code>GraphicAttribute</code>.
     * @see #getBounds()
     */
    public abstract float getDescent();

    /**
     * Returns the advance of this <code>GraphicAttribute</code>.  The
     * <code>GraphicAttribute</code> object's advance is the distance
     * from the point at which the graphic is rendered and the point where
     * the next character or graphic is rendered.  A graphic can be
     * rendered beyond its advance
     * @return the advance of this <code>GraphicAttribute</code>.
     * @see #getBounds()
     */
    public abstract float getAdvance();

    /**
     * Returns a {@link Rectangle2D} that encloses all of the
     * bits drawn by this <code>GraphicAttribute</code> relative to the
     * rendering position.
     * A graphic may be rendered beyond its origin, ascent, descent,
     * or advance;  but if it is, this method's implementation must
     * indicate where the graphic is rendered.
     * Default bounds is the rectangle (0, -ascent, advance, ascent+descent).
     * @return a <code>Rectangle2D</code> that encloses all of the bits
     * rendered by this <code>GraphicAttribute</code>.
     */
    public Rectangle2D getBounds() {
        float ascent = getAscent();
        return new Rectangle2D.Float(0, -ascent,
                                        getAdvance(), ascent+getDescent());
    }

    /**
     * Renders this <code>GraphicAttribute</code> at the specified 
     * location.
     * @param graphics the {@link Graphics2D} into which to render the
     * graphic
     * @param x,&nbsp;y the user-space coordinates where
     * the graphic is rendered
     */
    public abstract void draw(Graphics2D graphics, float x, float y);

    /**
     * Returns the alignment of this <code>GraphicAttribute</code>.
     * Alignment can be to a particular baseline, or to the absolute top
     * or bottom of a line.
     * @return the alignment of this <code>GraphicAttribute</code>.
     */
    public final int getAlignment() {

        return fAlignment;
    }

    /**
     * Returns the justification information for this 
     * <code>GraphicAttribute</code>.  Subclasses
     * can override this method to provide different justification
     * information.
     * @return a {@link GlyphJustificationInfo} object that contains the
     * justification information for this <code>GraphicAttribute</code>.
     */
    public GlyphJustificationInfo getJustificationInfo() {

        // should we cache this?
        float advance = getAdvance();

        return new GlyphJustificationInfo(
                                     advance,   // weight
                                     false,     // growAbsorb
                                     2,         // growPriority
                                     advance/3, // growLeftLimit
                                     advance/3, // growRightLimit
                                     false,     // shrinkAbsorb
                                     1,         // shrinkPriority
                                     0,         // shrinkLeftLimit
                                     0);        // shrinkRightLimit
    }
}