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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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/*
 * (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 jdk_internal.bidi;

import java.io.InvalidObjectException;
import java.util.HashMap;
import java.util.Map;

import jdk_internal.bidi.AttributedCharacterIterator.Attribute;

/**
 * The {@code TextAttribute} class defines attribute keys and attribute values
 * used for text rendering.
 * <p>
 * {@code TextAttribute} instances are used as attribute keys to identify
 * attributes in {@link java.awt.Font Font}, {@link java.awt.font.TextLayout
 * TextLayout}, {@link java.text.AttributedCharacterIterator
 * AttributedCharacterIterator}, and other classes handling text attributes.
 * Other constants defined in this class can be used as attribute values.
 * <p>
 * For each text attribute, the documentation provides:
 * <UL>
 * <LI>the type of its value,
 * <LI>the relevant predefined constants, if any
 * <LI>the default effect if the attribute is absent
 * <LI>the valid values if there are limitations
 * <LI>a description of the effect.
 * </UL>
 *
 * <H2>Values</H2>
 * <UL>
 * <LI>The values of attributes must always be immutable.
 * <LI>Where value limitations are given, any value outside of that set is
 * reserved for future use; the value will be treated as the default.
 * <LI>The value {@code null} is treated the same as the default value and
 * results in the default behavior.
 * <li>If the value is not of the proper type, the attribute will be ignored.
 * <li>The identity of the value does not matter, only the actual value. For
 * example, {@code TextAttribute.WEIGHT_BOLD} and {@code Float.valueOf(2.0f)}
 * indicate the same {@code WEIGHT}.
 * <li>Attribute values of type {@code Number} (used for {@code WEIGHT},
 * {@code WIDTH}, {@code POSTURE}, {@code SIZE}, {@code JUSTIFICATION}, and
 * {@code TRACKING}) can vary along their natural range and are not restricted
 * to the predefined constants. {@code Number.floatValue()} is used to get the
 * actual value from the {@code Number}.
 * <li>The values for {@code WEIGHT}, {@code WIDTH}, and {@code POSTURE} are
 * interpolated by the system, which can select the 'nearest available' font or
 * use other techniques to approximate the user's request.
 *
 * </UL>
 *
 * <h3>Summary of attributes</h3>
 *
 * <table style="width:95%;margin: 0px auto" class="striped">
 * <caption>Key, value type, principal constants, and default value behavior of
 * all TextAttributes</caption> <thead>
 * <tr>
 * <th scope="col">Key
 * <th scope="col">Value Type
 * <th scope="col">Principal Constants
 * <th scope="col">Default Value </thead> <tbody>
 * <tr>
 * <th scope="row">{@link #FAMILY}
 * <td>String
 * <td>See Font {@link java.awt.Font#DIALOG DIALOG},
 * {@link java.awt.Font#DIALOG_INPUT DIALOG_INPUT}, <br>
 * {@link java.awt.Font#SERIF SERIF}, {@link java.awt.Font#SANS_SERIF
 * SANS_SERIF}, and {@link java.awt.Font#MONOSPACED MONOSPACED}.
 * <td>"Default" (use platform default)
 * <tr>
 * <th scope="row">{@link #WEIGHT}
 * <td>Number
 * <td>WEIGHT_REGULAR, WEIGHT_BOLD
 * <td>WEIGHT_REGULAR
 * <tr>
 * <th scope="row">{@link #WIDTH}
 * <td>Number
 * <td>WIDTH_CONDENSED, WIDTH_REGULAR,<br>
 * WIDTH_EXTENDED
 * <td>WIDTH_REGULAR
 * <tr>
 * <th scope="row">{@link #POSTURE}
 * <td>Number
 * <td>POSTURE_REGULAR, POSTURE_OBLIQUE
 * <td>POSTURE_REGULAR
 * <tr>
 * <th scope="row">{@link #SIZE}
 * <td>Number
 * <td>none
 * <td>12.0
 * <tr>
 * <th scope="row">{@link #TRANSFORM}
 * <td>{@link TransformAttribute}
 * <td>See TransformAttribute {@link TransformAttribute#IDENTITY IDENTITY}
 * <td>TransformAttribute.IDENTITY
 * <tr>
 * <th scope="row">{@link #SUPERSCRIPT}
 * <td>Integer
 * <td>SUPERSCRIPT_SUPER, SUPERSCRIPT_SUB
 * <td>0 (use the standard glyphs and metrics)
 * <tr>
 * <th scope="row">{@link #FONT}
 * <td>{@link java.awt.Font}
 * <td>none
 * <td>null (do not override font resolution)
 * <tr>
 * <th scope="row">{@link #CHAR_REPLACEMENT}
 * <td>{@link GraphicAttribute}
 * <td>none
 * <td>null (draw text using font glyphs)
 * <tr>
 * <th scope="row">{@link #FOREGROUND}
 * <td>{@link java.awt.Paint}
 * <td>none
 * <td>null (use current graphics paint)
 * <tr>
 * <th scope="row">{@link #BACKGROUND}
 * <td>{@link java.awt.Paint}
 * <td>none
 * <td>null (do not render background)
 * <tr>
 * <th scope="row">{@link #UNDERLINE}
 * <td>Integer
 * <td>UNDERLINE_ON
 * <td>-1 (do not render underline)
 * <tr>
 * <th scope="row">{@link #STRIKETHROUGH}
 * <td>Boolean
 * <td>STRIKETHROUGH_ON
 * <td>false (do not render strikethrough)
 * <tr>
 * <th scope="row">{@link #RUN_DIRECTION}
 * <td>Boolean
 * <td>RUN_DIRECTION_LTR<br>
 * RUN_DIRECTION_RTL
 * <td>null (use {@link java.text.Bidi} standard default)
 * <tr>
 * <th scope="row">{@link #BIDI_EMBEDDING}
 * <td>Integer
 * <td>none
 * <td>0 (use base line direction)
 * <tr>
 * <th scope="row">{@link #JUSTIFICATION}
 * <td>Number
 * <td>JUSTIFICATION_FULL
 * <td>JUSTIFICATION_FULL
 * <tr>
 * <th scope="row">{@link #INPUT_METHOD_HIGHLIGHT}
 * <td>{@link java.awt.im.InputMethodHighlight}, <br>
 * {@link java.text.Annotation}
 * <td>(see class)
 * <td>null (do not apply input highlighting)
 * <tr>
 * <th scope="row">{@link #INPUT_METHOD_UNDERLINE}
 * <td>Integer
 * <td>UNDERLINE_LOW_ONE_PIXEL,<br>
 * UNDERLINE_LOW_TWO_PIXEL
 * <td>-1 (do not render underline)
 * <tr>
 * <th scope="row">{@link #SWAP_COLORS}
 * <td>Boolean
 * <td>SWAP_COLORS_ON
 * <td>false (do not swap colors)
 * <tr>
 * <th scope="row">{@link #NUMERIC_SHAPING}
 * <td>{@link java.awt.font.NumericShaper}
 * <td>none
 * <td>null (do not shape digits)
 * <tr>
 * <th scope="row">{@link #KERNING}
 * <td>Integer
 * <td>KERNING_ON
 * <td>0 (do not request kerning)
 * <tr>
 * <th scope="row">{@link #LIGATURES}
 * <td>Integer
 * <td>LIGATURES_ON
 * <td>0 (do not form optional ligatures)
 * <tr>
 * <th scope="row">{@link #TRACKING}
 * <td>Number
 * <td>TRACKING_LOOSE, TRACKING_TIGHT
 * <td>0 (do not add tracking)
 * </tr>
 * </tbody>
 * </table>
 *
 * @see java.awt.Font
 * @see java.awt.font.TextLayout
 * @see java.text.AttributedCharacterIterator
 */
public final class TextAttribute extends Attribute {

	// table of all instances in this class, used by readResolve
	private static final Map<String, TextAttribute> instanceMap = new HashMap<String, TextAttribute>(29);

	/**
	 * Constructs a {@code TextAttribute} with the specified name.
	 * 
	 * @param name the attribute name to assign to this {@code TextAttribute}
	 */
	protected TextAttribute(String name) {
		super(name);
		if (this.getClass() == TextAttribute.class) {
			instanceMap.put(name, this);
		}
	}

	/**
	 * Resolves instances being deserialized to the predefined constants.
	 */
	protected Object readResolve() throws InvalidObjectException {
		if (this.getClass() != TextAttribute.class) {
			throw new InvalidObjectException("subclass didn't correctly implement readResolve");
		}

		TextAttribute instance = instanceMap.get(getName());
		if (instance != null) {
			return instance;
		} else {
			throw new InvalidObjectException("unknown attribute name");
		}
	}

	/**
	 * Use serialVersionUID from JDK 1.2 for interoperability. 1.2 will throw an
	 * InvalidObjectException if ever asked to deserialize INPUT_METHOD_UNDERLINE.
	 * This shouldn't happen in real life.
	 */
	private static final long serialVersionUID = 7744112784117861702L;

	//
	// For use with Font.
	//

	/**
	 * Attribute key for the font name. Values are instances of
	 * <b>{@code String}</b>. The default value is {@code "Default"}, which causes
	 * the platform default font family to be used.
	 *
	 * <p>
	 * The {@code Font} class defines constants for the logical font names
	 * {@link java.awt.Font#DIALOG DIALOG}, {@link java.awt.Font#DIALOG_INPUT
	 * DIALOG_INPUT}, {@link java.awt.Font#SANS_SERIF SANS_SERIF},
	 * {@link java.awt.Font#SERIF SERIF}, and {@link java.awt.Font#MONOSPACED
	 * MONOSPACED}.
	 *
	 * <p>
	 * This defines the value passed as {@code name} to the {@code Font}
	 * constructor. Both logical and physical font names are allowed. If a font with
	 * the requested name is not found, the default font is used.
	 *
	 * <p>
	 * <em>Note:</em> This attribute is unfortunately misnamed, as it specifies the
	 * face name and not just the family. Thus values such as "Lucida Sans Bold"
	 * will select that face if it exists. Note, though, that if the requested face
	 * does not exist, the default will be used with <em>regular</em> weight. The
	 * "Bold" in the name is part of the face name, not a separate request that the
	 * font's weight be bold.
	 * </p>
	 */
	public static final TextAttribute FAMILY = new TextAttribute("family");

	/**
	 * Attribute key for the weight of a font. Values are instances of
	 * <b>{@code Number}</b>. The default value is {@code WEIGHT_REGULAR}.
	 *
	 * <p>
	 * Several constant values are provided, see {@link #WEIGHT_EXTRA_LIGHT},
	 * {@link #WEIGHT_LIGHT}, {@link #WEIGHT_DEMILIGHT}, {@link #WEIGHT_REGULAR},
	 * {@link #WEIGHT_SEMIBOLD}, {@link #WEIGHT_MEDIUM}, {@link #WEIGHT_DEMIBOLD},
	 * {@link #WEIGHT_BOLD}, {@link #WEIGHT_HEAVY}, {@link #WEIGHT_EXTRABOLD}, and
	 * {@link #WEIGHT_ULTRABOLD}. The value {@code WEIGHT_BOLD} corresponds to the
	 * style value {@code Font.BOLD} as passed to the {@code Font} constructor.
	 *
	 * <p>
	 * The value is roughly the ratio of the stem width to that of the regular
	 * weight.
	 *
	 * <p>
	 * The system can interpolate the provided value.
	 */
	public static final TextAttribute WEIGHT = new TextAttribute("weight");

	/**
	 * The lightest predefined weight.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_EXTRA_LIGHT = Float.valueOf(0.5f);

	/**
	 * The standard light weight.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_LIGHT = Float.valueOf(0.75f);

	/**
	 * An intermediate weight between {@code WEIGHT_LIGHT} and
	 * {@code WEIGHT_STANDARD}.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_DEMILIGHT = Float.valueOf(0.875f);

	/**
	 * The standard weight. This is the default value for {@code WEIGHT}.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_REGULAR = Float.valueOf(1.0f);

	/**
	 * A moderately heavier weight than {@code WEIGHT_REGULAR}.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_SEMIBOLD = Float.valueOf(1.25f);

	/**
	 * An intermediate weight between {@code WEIGHT_REGULAR} and
	 * {@code WEIGHT_BOLD}.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_MEDIUM = Float.valueOf(1.5f);

	/**
	 * A moderately lighter weight than {@code WEIGHT_BOLD}.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_DEMIBOLD = Float.valueOf(1.75f);

	/**
	 * The standard bold weight.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_BOLD = Float.valueOf(2.0f);

	/**
	 * A moderately heavier weight than {@code WEIGHT_BOLD}.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_HEAVY = Float.valueOf(2.25f);

	/**
	 * An extra heavy weight.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_EXTRABOLD = Float.valueOf(2.5f);

	/**
	 * The heaviest predefined weight.
	 * 
	 * @see #WEIGHT
	 */
	public static final Float WEIGHT_ULTRABOLD = Float.valueOf(2.75f);

	/**
	 * Attribute key for the width of a font. Values are instances of
	 * <b>{@code Number}</b>. The default value is {@code WIDTH_REGULAR}.
	 *
	 * <p>
	 * Several constant values are provided, see {@link #WIDTH_CONDENSED},
	 * {@link #WIDTH_SEMI_CONDENSED}, {@link #WIDTH_REGULAR},
	 * {@link #WIDTH_SEMI_EXTENDED}, {@link #WIDTH_EXTENDED}.
	 *
	 * <p>
	 * The value is roughly the ratio of the advance width to that of the regular
	 * width.
	 *
	 * <p>
	 * The system can interpolate the provided value.
	 */
	public static final TextAttribute WIDTH = new TextAttribute("width");

	/**
	 * The most condensed predefined width.
	 * 
	 * @see #WIDTH
	 */
	public static final Float WIDTH_CONDENSED = Float.valueOf(0.75f);

	/**
	 * A moderately condensed width.
	 * 
	 * @see #WIDTH
	 */
	public static final Float WIDTH_SEMI_CONDENSED = Float.valueOf(0.875f);

	/**
	 * The standard width. This is the default value for {@code WIDTH}.
	 * 
	 * @see #WIDTH
	 */
	public static final Float WIDTH_REGULAR = Float.valueOf(1.0f);

	/**
	 * A moderately extended width.
	 * 
	 * @see #WIDTH
	 */
	public static final Float WIDTH_SEMI_EXTENDED = Float.valueOf(1.25f);

	/**
	 * The most extended predefined width.
	 * 
	 * @see #WIDTH
	 */
	public static final Float WIDTH_EXTENDED = Float.valueOf(1.5f);

	/**
	 * Attribute key for the posture of a font. Values are instances of
	 * <b>{@code Number}</b>. The default value is {@code POSTURE_REGULAR}.
	 *
	 * <p>
	 * Two constant values are provided, {@link #POSTURE_REGULAR} and
	 * {@link #POSTURE_OBLIQUE}. The value {@code POSTURE_OBLIQUE} corresponds to
	 * the style value {@code Font.ITALIC} as passed to the {@code Font}
	 * constructor.
	 *
	 * <p>
	 * The value is roughly the slope of the stems of the font, expressed as the run
	 * over the rise. Positive values lean right.
	 *
	 * <p>
	 * The system can interpolate the provided value.
	 *
	 * <p>
	 * This will affect the font's italic angle as returned by
	 * {@code Font.getItalicAngle}.
	 *
	 * @see java.awt.Font#getItalicAngle()
	 */
	public static final TextAttribute POSTURE = new TextAttribute("posture");

	/**
	 * The standard posture, upright. This is the default value for {@code POSTURE}.
	 * 
	 * @see #POSTURE
	 */
	public static final Float POSTURE_REGULAR = Float.valueOf(0.0f);

	/**
	 * The standard italic posture.
	 * 
	 * @see #POSTURE
	 */
	public static final Float POSTURE_OBLIQUE = Float.valueOf(0.20f);

	/**
	 * Attribute key for the font size. Values are instances of
	 * <b>{@code Number}</b>. The default value is 12pt.
	 *
	 * <p>
	 * This corresponds to the {@code size} parameter to the {@code Font}
	 * constructor.
	 *
	 * <p>
	 * Very large or small sizes will impact rendering performance, and the
	 * rendering system might not render text at these sizes. Negative sizes are
	 * illegal and result in the default size.
	 *
	 * <p>
	 * Note that the appearance and metrics of a 12pt font with a 2x transform might
	 * be different than that of a 24 point font with no transform.
	 */
	public static final TextAttribute SIZE = new TextAttribute("size");

	/**
	 * Attribute key for the transform of a font. Values are instances of
	 * <b>{@code TransformAttribute}</b>. The default value is
	 * {@code TransformAttribute.IDENTITY}.
	 *
	 * <p>
	 * The {@code TransformAttribute} class defines the constant
	 * {@link TransformAttribute#IDENTITY IDENTITY}.
	 *
	 * <p>
	 * This corresponds to the transform passed to
	 * {@code Font.deriveFont(AffineTransform)}. Since that transform is mutable and
	 * {@code TextAttribute} values must not be, the {@code TransformAttribute}
	 * wrapper class is used.
	 *
	 * <p>
	 * The primary intent is to support scaling and skewing, though other effects
	 * are possible.
	 * </p>
	 *
	 * <p>
	 * Some transforms will cause the baseline to be rotated and/or shifted. The
	 * text and the baseline are transformed together so that the text follows the
	 * new baseline. For example, with text on a horizontal baseline, the new
	 * baseline follows the direction of the unit x vector passed through the
	 * transform. Text metrics are measured against this new baseline. So, for
	 * example, with other things being equal, text rendered with a rotated
	 * TRANSFORM and an unrotated TRANSFORM will measure as having the same ascent,
	 * descent, and advance.
	 * </p>
	 *
	 * <p>
	 * In styled text, the baselines for each such run are aligned one after the
	 * other to potentially create a non-linear baseline for the entire run of text.
	 * For more information, see {@link TextLayout#getLayoutPath}.
	 * </p>
	 *
	 * @see TransformAttribute
	 * @see java.awt.geom.AffineTransform
	 */
	public static final TextAttribute TRANSFORM = new TextAttribute("transform");

	/**
	 * Attribute key for superscripting and subscripting. Values are instances of
	 * <b>{@code Integer}</b>. The default value is 0, which means that no
	 * superscript or subscript is used.
	 *
	 * <p>
	 * Two constant values are provided, see {@link #SUPERSCRIPT_SUPER} and
	 * {@link #SUPERSCRIPT_SUB}. These have the values 1 and -1 respectively. Values
	 * of greater magnitude define greater levels of superscript or subscripting,
	 * for example, 2 corresponds to super-superscript, 3 to
	 * super-super-superscript, and similarly for negative values and subscript, up
	 * to a level of 7 (or -7). Values beyond this range are reserved; behavior is
	 * platform-dependent.
	 *
	 * <p>
	 * {@code SUPERSCRIPT} can impact the ascent and descent of a font. The ascent
	 * and descent can never become negative, however.
	 */
	public static final TextAttribute SUPERSCRIPT = new TextAttribute("superscript");

	/**
	 * Standard superscript.
	 * 
	 * @see #SUPERSCRIPT
	 */
	public static final Integer SUPERSCRIPT_SUPER = Integer.valueOf(1);

	/**
	 * Standard subscript.
	 * 
	 * @see #SUPERSCRIPT
	 */
	public static final Integer SUPERSCRIPT_SUB = Integer.valueOf(-1);

	/**
	 * Attribute key used to provide the font to use to render text. Values are
	 * instances of {@link java.awt.Font}. The default value is null, indicating
	 * that normal resolution of a {@code Font} from attributes should be performed.
	 *
	 * <p>
	 * {@code TextLayout} and {@code AttributedCharacterIterator} work in terms of
	 * {@code Maps} of {@code TextAttributes}. Normally, all the attributes are
	 * examined and used to select and configure a {@code Font} instance. If a
	 * {@code FONT} attribute is present, though, its associated {@code Font} will
	 * be used. This provides a way for users to override the resolution of font
	 * attributes into a {@code Font}, or force use of a particular {@code Font}
	 * instance. This also allows users to specify subclasses of {@code Font} in
	 * cases where a {@code Font} can be subclassed.
	 *
	 * <p>
	 * {@code FONT} is used for special situations where clients already have a
	 * {@code Font} instance but still need to use {@code Map}-based APIs.
	 * Typically, there will be no other attributes in the {@code Map} except the
	 * {@code FONT} attribute. With {@code Map}-based APIs the common case is to
	 * specify all attributes individually, so {@code FONT} is not needed or
	 * desirable.
	 *
	 * <p>
	 * However, if both {@code FONT} and other attributes are present in the
	 * {@code Map}, the rendering system will merge the attributes defined in the
	 * {@code Font} with the additional attributes. This merging process classifies
	 * {@code TextAttributes} into two groups. One group, the 'primary' group, is
	 * considered fundamental to the selection and metric behavior of a font. These
	 * attributes are {@code FAMILY}, {@code WEIGHT}, {@code WIDTH},
	 * {@code POSTURE}, {@code SIZE}, {@code TRANSFORM}, {@code SUPERSCRIPT}, and
	 * {@code TRACKING}. The other group, the 'secondary' group, consists of all
	 * other defined attributes, with the exception of {@code FONT} itself.
	 *
	 * <p>
	 * To generate the new {@code Map}, first the {@code Font} is obtained from the
	 * {@code FONT} attribute, and <em>all</em> of its attributes extracted into a
	 * new {@code Map}. Then only the <em>secondary</em> attributes from the
	 * original {@code Map} are added to those in the new {@code Map}. Thus the
	 * values of primary attributes come solely from the {@code Font}, and the
	 * values of secondary attributes originate with the {@code Font} but can be
	 * overridden by other values in the {@code Map}.
	 *
	 * <p>
	 * <em>Note:</em>{@code Font's Map}-based constructor and {@code deriveFont}
	 * methods do not process the {@code FONT} attribute, as these are used to
	 * create new {@code Font} objects. Instead, {@link java.awt.Font#getFont(Map)
	 * Font.getFont(Map)} should be used to handle the {@code FONT} attribute.
	 *
	 * @see java.awt.Font
	 */
	public static final TextAttribute FONT = new TextAttribute("font");

	/**
	 * Attribute key for a user-defined glyph to display in lieu of the font's
	 * standard glyph for a character. Values are instances of GraphicAttribute. The
	 * default value is null, indicating that the standard glyphs provided by the
	 * font should be used.
	 *
	 * <p>
	 * This attribute is used to reserve space for a graphic or other component
	 * embedded in a line of text. It is required for correct positioning of
	 * 'inline' components within a line when bidirectional reordering (see
	 * {@link java.text.Bidi}) is performed. Each character (Unicode code point)
	 * will be rendered using the provided GraphicAttribute. Typically, the
	 * characters to which this attribute is applied should be
	 * <code>&#92;uFFFC</code>.
	 *
	 * <p>
	 * The GraphicAttribute determines the logical and visual bounds of the text;
	 * the actual Font values are ignored.
	 *
	 * @see GraphicAttribute
	 */
	public static final TextAttribute CHAR_REPLACEMENT = new TextAttribute("char_replacement");

	//
	// Adornments added to text.
	//

	/**
	 * Attribute key for the paint used to render the text. Values are instances of
	 * <b>{@code Paint}</b>. The default value is null, indicating that the
	 * {@code Paint} set on the {@code Graphics2D} at the time of rendering is used.
	 *
	 * <p>
	 * Glyphs will be rendered using this {@code Paint} regardless of the
	 * {@code Paint} value set on the {@code Graphics} (but see
	 * {@link #SWAP_COLORS}).
	 *
	 * @see java.awt.Paint
	 * @see #SWAP_COLORS
	 */
	public static final TextAttribute FOREGROUND = new TextAttribute("foreground");

	/**
	 * Attribute key for the paint used to render the background of the text. Values
	 * are instances of <b>{@code Paint}</b>. The default value is null, indicating
	 * that the background should not be rendered.
	 *
	 * <p>
	 * The logical bounds of the text will be filled using this {@code Paint}, and
	 * then the text will be rendered on top of it (but see {@link #SWAP_COLORS}).
	 *
	 * <p>
	 * The visual bounds of the text is extended to include the logical bounds, if
	 * necessary. The outline is not affected.
	 *
	 * @see java.awt.Paint
	 * @see #SWAP_COLORS
	 */
	public static final TextAttribute BACKGROUND = new TextAttribute("background");

	/**
	 * Attribute key for underline. Values are instances of <b>{@code Integer}</b>.
	 * The default value is -1, which means no underline.
	 *
	 * <p>
	 * The constant value {@link #UNDERLINE_ON} is provided.
	 *
	 * <p>
	 * The underline affects both the visual bounds and the outline of the text.
	 */
	public static final TextAttribute UNDERLINE = new TextAttribute("underline");

	/**
	 * Standard underline.
	 *
	 * @see #UNDERLINE
	 */
	public static final Integer UNDERLINE_ON = Integer.valueOf(0);

	/**
	 * Attribute key for strikethrough. Values are instances of
	 * <b>{@code Boolean}</b>. The default value is {@code false}, which means no
	 * strikethrough.
	 *
	 * <p>
	 * The constant value {@link #STRIKETHROUGH_ON} is provided.
	 *
	 * <p>
	 * The strikethrough affects both the visual bounds and the outline of the text.
	 */
	public static final TextAttribute STRIKETHROUGH = new TextAttribute("strikethrough");

	/**
	 * A single strikethrough.
	 *
	 * @see #STRIKETHROUGH
	 */
	public static final Boolean STRIKETHROUGH_ON = Boolean.TRUE;

	//
	// Attributes use to control layout of text on a line.
	//

	/**
	 * Attribute key for the run direction of the line. Values are instances of
	 * <b>{@code Boolean}</b>. The default value is null, which indicates that the
	 * standard Bidi algorithm for determining run direction should be used with the
	 * value {@link java.text.Bidi#DIRECTION_DEFAULT_LEFT_TO_RIGHT}.
	 *
	 * <p>
	 * The constants {@link #RUN_DIRECTION_RTL} and {@link #RUN_DIRECTION_LTR} are
	 * provided.
	 *
	 * <p>
	 * This determines the value passed to the {@link java.text.Bidi} constructor to
	 * select the primary direction of the text in the paragraph.
	 *
	 * <p>
	 * <em>Note:</em> This attribute should have the same value for all the text in
	 * a paragraph, otherwise the behavior is undetermined.
	 *
	 * @see java.text.Bidi
	 */
	public static final TextAttribute RUN_DIRECTION = new TextAttribute("run_direction");

	/**
	 * Left-to-right run direction.
	 * 
	 * @see #RUN_DIRECTION
	 */
	public static final Boolean RUN_DIRECTION_LTR = Boolean.FALSE;

	/**
	 * Right-to-left run direction.
	 * 
	 * @see #RUN_DIRECTION
	 */
	public static final Boolean RUN_DIRECTION_RTL = Boolean.TRUE;

	/**
	 * Attribute key for the embedding level of the text. Values are instances of
	 * <b>{@code Integer}</b>. The default value is {@code null}, indicating that
	 * the Bidirectional algorithm should run without explicit embeddings.
	 *
	 * <p>
	 * Positive values 1 through 61 are <em>embedding</em> levels, negative values
	 * -1 through -61 are <em>override</em> levels. The value 0 means that the base
	 * line direction is used. These levels are passed in the embedding levels array
	 * to the {@link java.text.Bidi} constructor.
	 *
	 * <p>
	 * <em>Note:</em> When this attribute is present anywhere in a paragraph, then
	 * any Unicode bidi control characters (RLO, LRO, RLE, LRE, and PDF) in the
	 * paragraph are disregarded, and runs of text where this attribute is not
	 * present are treated as though it were present and had the value 0.
	 *
	 * @see java.text.Bidi
	 */
	public static final TextAttribute BIDI_EMBEDDING = new TextAttribute("bidi_embedding");

	/**
	 * Attribute key for the justification of a paragraph. Values are instances of
	 * <b>{@code Number}</b>. The default value is 1, indicating that justification
	 * should use the full width provided. Values are pinned to the range [0..1].
	 *
	 * <p>
	 * The constants {@link #JUSTIFICATION_FULL} and {@link #JUSTIFICATION_NONE} are
	 * provided.
	 *
	 * <p>
	 * Specifies the fraction of the extra space to use when justification is
	 * requested on a {@code TextLayout}. For example, if the line is 50 points wide
	 * and it is requested to justify to 70 points, a value of 0.75 will pad to use
	 * three-quarters of the remaining space, or 15 points, so that the resulting
	 * line will be 65 points in length.
	 *
	 * <p>
	 * <em>Note:</em> This should have the same value for all the text in a
	 * paragraph, otherwise the behavior is undetermined.
	 *
	 * @see TextLayout#getJustifiedLayout
	 */
	public static final TextAttribute JUSTIFICATION = new TextAttribute("justification");

	/**
	 * Justify the line to the full requested width. This is the default value for
	 * {@code JUSTIFICATION}.
	 * 
	 * @see #JUSTIFICATION
	 */
	public static final Float JUSTIFICATION_FULL = Float.valueOf(1.0f);

	/**
	 * Do not allow the line to be justified.
	 * 
	 * @see #JUSTIFICATION
	 */
	public static final Float JUSTIFICATION_NONE = Float.valueOf(0.0f);

	//
	// For use by input method.
	//

	/**
	 * Attribute key for input method highlight styles.
	 *
	 * <p>
	 * Values are instances of {@link java.awt.im.InputMethodHighlight} or
	 * {@link java.text.Annotation}. The default value is {@code null}, which means
	 * that input method styles should not be applied before rendering.
	 *
	 * <p>
	 * If adjacent runs of text with the same {@code InputMethodHighlight} need to
	 * be rendered separately, the {@code InputMethodHighlights} should be wrapped
	 * in {@code Annotation} instances.
	 *
	 * <p>
	 * Input method highlights are used while text is being composed by an input
	 * method. Text editing components should retain them even if they generally
	 * only deal with unstyled text, and make them available to the drawing
	 * routines.
	 *
	 * @see java.awt.Font
	 * @see java.awt.im.InputMethodHighlight
	 * @see java.text.Annotation
	 */
	public static final TextAttribute INPUT_METHOD_HIGHLIGHT = new TextAttribute("input method highlight");

	/**
	 * Attribute key for input method underlines. Values are instances of
	 * <b>{@code Integer}</b>. The default value is {@code -1}, which means no
	 * underline.
	 *
	 * <p>
	 * Several constant values are provided, see {@link #UNDERLINE_LOW_ONE_PIXEL},
	 * {@link #UNDERLINE_LOW_TWO_PIXEL}, {@link #UNDERLINE_LOW_DOTTED},
	 * {@link #UNDERLINE_LOW_GRAY}, and {@link #UNDERLINE_LOW_DASHED}.
	 *
	 * <p>
	 * This may be used in conjunction with {@link #UNDERLINE} if desired. The
	 * primary purpose is for use by input methods. Other use of these underlines
	 * for simple ornamentation might confuse users.
	 *
	 * <p>
	 * The input method underline affects both the visual bounds and the outline of
	 * the text.
	 *
	 * @since 1.3
	 */
	public static final TextAttribute INPUT_METHOD_UNDERLINE = new TextAttribute("input method underline");

	/**
	 * Single pixel solid low underline.
	 * 
	 * @see #INPUT_METHOD_UNDERLINE
	 * @since 1.3
	 */
	public static final Integer UNDERLINE_LOW_ONE_PIXEL = Integer.valueOf(1);

	/**
	 * Double pixel solid low underline.
	 * 
	 * @see #INPUT_METHOD_UNDERLINE
	 * @since 1.3
	 */
	public static final Integer UNDERLINE_LOW_TWO_PIXEL = Integer.valueOf(2);

	/**
	 * Single pixel dotted low underline.
	 * 
	 * @see #INPUT_METHOD_UNDERLINE
	 * @since 1.3
	 */
	public static final Integer UNDERLINE_LOW_DOTTED = Integer.valueOf(3);

	/**
	 * Double pixel gray low underline.
	 * 
	 * @see #INPUT_METHOD_UNDERLINE
	 * @since 1.3
	 */
	public static final Integer UNDERLINE_LOW_GRAY = Integer.valueOf(4);

	/**
	 * Single pixel dashed low underline.
	 * 
	 * @see #INPUT_METHOD_UNDERLINE
	 * @since 1.3
	 */
	public static final Integer UNDERLINE_LOW_DASHED = Integer.valueOf(5);

	/**
	 * Attribute key for swapping foreground and background {@code Paints}. Values
	 * are instances of <b>{@code Boolean}</b>. The default value is {@code false},
	 * which means do not swap colors.
	 *
	 * <p>
	 * The constant value {@link #SWAP_COLORS_ON} is defined.
	 *
	 * <p>
	 * If the {@link #FOREGROUND} attribute is set, its {@code Paint} will be used
	 * as the background, otherwise the {@code Paint} currently on the
	 * {@code Graphics} will be used. If the {@link #BACKGROUND} attribute is set,
	 * its {@code Paint} will be used as the foreground, otherwise the system will
	 * find a contrasting color to the (resolved) background so that the text will
	 * be visible.
	 *
	 * @see #FOREGROUND
	 * @see #BACKGROUND
	 */
	public static final TextAttribute SWAP_COLORS = new TextAttribute("swap_colors");

	/**
	 * Swap foreground and background.
	 * 
	 * @see #SWAP_COLORS
	 * @since 1.3
	 */
	public static final Boolean SWAP_COLORS_ON = Boolean.TRUE;

	/**
	 * Attribute key for converting ASCII decimal digits to other decimal ranges.
	 * Values are instances of {@link NumericShaper}. The default is {@code null},
	 * which means do not perform numeric shaping.
	 *
	 * <p>
	 * When a numeric shaper is defined, the text is first processed by the shaper
	 * before any other analysis of the text is performed.
	 *
	 * <p>
	 * <em>Note:</em> This should have the same value for all the text in the
	 * paragraph, otherwise the behavior is undetermined.
	 *
	 * @see NumericShaper
	 * @since 1.4
	 */
	public static final TextAttribute NUMERIC_SHAPING = new TextAttribute("numeric_shaping");

	/**
	 * Attribute key to request kerning. Values are instances of
	 * <b>{@code Integer}</b>. The default value is {@code 0}, which does not
	 * request kerning.
	 *
	 * <p>
	 * The constant value {@link #KERNING_ON} is provided.
	 *
	 * <p>
	 * The default advances of single characters are not appropriate for some
	 * character sequences, for example "To" or "AWAY". Without kerning the adjacent
	 * characters appear to be separated by too much space. Kerning causes selected
	 * sequences of characters to be spaced differently for a more pleasing visual
	 * appearance.
	 *
	 * @since 1.6
	 */
	public static final TextAttribute KERNING = new TextAttribute("kerning");

	/**
	 * Request standard kerning.
	 * 
	 * @see #KERNING
	 * @since 1.6
	 */
	public static final Integer KERNING_ON = Integer.valueOf(1);

	/**
	 * Attribute key for enabling optional ligatures. Values are instances of
	 * <b>{@code Integer}</b>. The default value is {@code 0}, which means do not
	 * use optional ligatures.
	 *
	 * <p>
	 * The constant value {@link #LIGATURES_ON} is defined.
	 *
	 * <p>
	 * Ligatures required by the writing system are always enabled.
	 *
	 * @since 1.6
	 */
	public static final TextAttribute LIGATURES = new TextAttribute("ligatures");

	/**
	 * Request standard optional ligatures.
	 * 
	 * @see #LIGATURES
	 * @since 1.6
	 */
	public static final Integer LIGATURES_ON = Integer.valueOf(1);

	/**
	 * Attribute key to control tracking. Values are instances of
	 * <b>{@code Number}</b>. The default value is {@code 0}, which means no
	 * additional tracking.
	 *
	 * <p>
	 * The constant values {@link #TRACKING_TIGHT} and {@link #TRACKING_LOOSE} are
	 * provided.
	 *
	 * <p>
	 * The tracking value is multiplied by the font point size and passed through
	 * the font transform to determine an additional amount to add to the advance of
	 * each glyph cluster. Positive tracking values will inhibit formation of
	 * optional ligatures. Tracking values are typically between {@code -0.1} and
	 * {@code 0.3}; values outside this range are generally not desirable.
	 *
	 * @since 1.6
	 */
	public static final TextAttribute TRACKING = new TextAttribute("tracking");

	/**
	 * Perform tight tracking.
	 * 
	 * @see #TRACKING
	 * @since 1.6
	 */
	public static final Float TRACKING_TIGHT = Float.valueOf(-.04f);

	/**
	 * Perform loose tracking.
	 * 
	 * @see #TRACKING
	 * @since 1.6
	 */
	public static final Float TRACKING_LOOSE = Float.valueOf(.04f);
}