/*
 * @(#)FontMetrics.java	1.42 00/02/02
 *
 * Copyright 1995-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package java.awt;

import java.awt.Graphics2D;
import java.awt.font.FontRenderContext;
import java.awt.font.LineMetrics;
import java.awt.geom.Rectangle2D;
import java.text.CharacterIterator;

/**
 * The <code>FontMetrics</code> class defines a font metrics object, which
 * encapsulates information about the rendering of a particular font on a
 * particular screen. 
 * <p>
 * <b>Note to subclassers</b>: Since many of these methods form closed,
 * mutually recursive loops, you must take care that you implement
 * at least one of the methods in each such loop to prevent
 * infinite recursion when your subclass is used.
 * In particular, the following is the minimal suggested set of methods
 * to override in order to ensure correctness and prevent infinite
 * recursion (though other subsets are equally feasible):
 * <ul>
 * <li>{@link #getAscent()}
 * <li>{@link #getLeading()}
 * <li>{@link #getMaxAdvance()}
 * <li>{@link #charWidth(char)}
 * <li>{@link #charsWidth(char[], int, int)}
 * </ul>
 * <p>
 * <img src="doc-files/FontMetrics-1.gif" border=15 align
 * ALIGN=right HSPACE=10 VSPACE=7>
 * Note that the implementations of these methods are
 * inefficient, so they are usually overridden with more efficient
 * toolkit-specific implementations.
 * <p>
 * When an application asks AWT to place a character at the position
 * (<i>x</i>, <i>y</i>), the character is placed so that its
 * reference point (shown as the dot in the accompanying image) is
 * put at that position. The reference point specifies a horizontal
 * line called the <i>baseline</i> of the character. In normal
 * printing, the baselines of characters should align.
 * <p>
 * In addition, every character in a font has an <i>ascent</i>, a
 * <i>descent</i>, and an <i>advance width</i>. The ascent is the
 * amount by which the character ascends above the baseline. The
 * descent is the amount by which the character descends below the
 * baseline. The advance width indicates the position at which AWT
 * should place the next character.
 * <p>
 * An array of characters or a string can also have an ascent, a
 * descent, and an advance width. The ascent of the array is the
 * maximum ascent of any character in the array. The descent is the
 * maximum descent of any character in the array. The advance width
 * is the sum of the advance widths of each of the characters in the
 * character array.  The advance of a <code>String</code> is the
 * distance along the baseline of the <code>String</code>.  This 
 * distance is the width that should be used for centering or 
 * right-aligning the <code>String</code>.
 * Note that the advance of a <code>String</code> is not necessarily 
 * the sum of the advances of its characters measured in isolation 
 * because the width of a character can vary depending on its context.  
 * For example, in Arabic text, the shape of a character can change 
 * in order to connect to other characters.  Also, in some scripts, 
 * certain character sequences can be represented by a single shape, 
 * called a <em>ligature</em>.  Measuring characters individually does
 * not account for these transformations.
 *
 * @version 	1.21 03/18/98
 * @author 	Jim Graham
 * @see         java.awt.Font
 * @since       JDK1.0
 */
public abstract class FontMetrics implements java.io.Serializable {

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

    /**
     * The actual {@link Font} from which the font metrics are
     * created. 
     * This cannot be null.
     *
     * @serial
     * @see #getFont()
     */
    protected Font font;

    /*
     * JDK 1.1 serialVersionUID
     */
    private static final long serialVersionUID = 1681126225205050147L;

    /**
     * Creates a new <code>FontMetrics</code> object for finding out
     * height and width information about the specified <code>Font</code> 
     * and specific character glyphs in that <code>Font</code>.
     * @param     font the <code>Font</code>
     * @see       java.awt.Font
     */
    protected FontMetrics(Font font) {
	this.font = font;
    }

    /**
     * Gets the <code>Font</code> described by this
     * <code>FontMetrics</code> object.
     * @return    the <code>Font</code> described by this 
     * <code>FontMetrics</code> object.
     */
    public Font getFont() {
	return font;
    }

    /**
     * Determines the <em>standard leading</em> of the 
     * <code>Font</code> described by this <code>FontMetrics</code>
     * object.  The standard leading, or
     * interline spacing, is the logical amount of space to be reserved
     * between the descent of one line of text and the ascent of the next
     * line. The height metric is calculated to include this extra space.
     * @return    the standard leading of the <code>Font</code>.
     * @see   #getHeight()
     * @see   #getAscent()
     * @see   #getDescent()
     */
    public int getLeading() {
	return 0;
    }

    /**
     * Determines the <em>font ascent</em> of the <code>Font</code> 
     * described by this <code>FontMetrics</code> object. The font ascent
     * is the distance from the font's baseline to the top of most
     * alphanumeric characters. Some characters in the <code>Font</code> 
     * might extend above the font ascent line.
     * @return     the font ascent of the <code>Font</code>.
     * @see        #getMaxAscent()
     */
    public int getAscent() {
	return font.getSize();
    }

    /**
     * Determines the <em>font descent</em> of the <code>Font</code> 
     * described by this
     * <code>FontMetrics</code> object. The font descent is the distance
     * from the font's baseline to the bottom of most alphanumeric
     * characters with descenders. Some characters in the
     * <code>Font</code> might extend
     * below the font descent line.
     * @return     the font descent of the <code>Font</code>.
     * @see        #getMaxDescent()
     */
    public int getDescent() {
	return 0;
    }

    /**
     * Gets the standard height of a line of text in this font.  This
     * is the distance between the baseline of adjacent lines of text.
     * It is the sum of the leading + ascent + descent.  There is no
     * guarantee that lines of text spaced at this distance are
     * disjoint; such lines may overlap if some characters overshoot
     * either the standard ascent or the standard descent metric.
     * @return    the standard height of the font.
     * @see       #getLeading()
     * @see       #getAscent()
     * @see       #getDescent()
     */
    public int getHeight() {
	return getLeading() + getAscent() + getDescent();
    }

    /**
     * Determines the maximum ascent of the <code>Font</code> 
     * described by this <code>FontMetrics</code> object.  No character 
     * extends further above the font's baseline than this height.
     * @return    the maximum ascent of any character in the 
     * <code>Font</code>.
     * @see       #getAscent()
     */
    public int getMaxAscent() {
	return getAscent();
    }

    /**
     * Determines the maximum descent of the <code>Font</code> 
     * described by this <code>FontMetrics</code> object.  No character 
     * extends further below the font's baseline than this height.
     * @return    the maximum descent of any character in the
     * <code>Font</code>.
     * @see       #getDescent()
     */
    public int getMaxDescent() {
	return getDescent();
    }

    /**
     * For backward compatibility only.
     * @see #getMaxDescent()
     * @deprecated As of JDK version 1.1.1,
     * replaced by <code>getMaxDescent()</code>.
     */
    public int getMaxDecent() {
	return getMaxDescent();
    }

    /**
     * Gets the maximum advance width of any character in this 
     * <code>Font</code>.  The advance is the
     * distance from the leftmost point to the rightmost point on the
     * string's baseline.  The advance of a <code>String</code> is    
     * not necessarily the sum of the advances of its characters.
     * @return    the maximum advance width of any character
     *            in the <code>Font</code>, or <code>-1</code> if the
     *            maximum advance width is not known.
     */
    public int getMaxAdvance() {
	return -1;
    }

    /**
     * Returns the advance width of the specified character in this 
     * <code>Font</code>.  The advance is the
     * distance from the leftmost point to the rightmost point on the
     * character's baseline.  Note that the advance of a
     * <code>String</code> is not necessarily the sum of the advances 
     * of its characters.
     * @param ch the character to be measured
     * @return    the advance width of the specified <code>char</code>
     *                 in the <code>Font</code> described by this
     *			<code>FontMetrics</code> object.
     * @see       #charsWidth(char[], int, int)
     * @see       #stringWidth(String)
     */
    public int charWidth(int ch) {
	return charWidth((char)ch);
    }

    /**
     * Returns the advance width of the specified character in this 
     * <code>Font</code>.  The advance is the
     * distance from the leftmost point to the rightmost point on the
     * character's baseline.  Note that the advance of a
     * <code>String</code> is not necessarily the sum of the advances 
     * of its characters.
     * @return     the advance width of the specified <code>char</code>
     *                  in the <code>Font</code> described by this 
     *			<code>FontMetrics</code> object.
     * @see        #charsWidth(char[], int, int)
     * @see        #stringWidth(String)
     */
    public int charWidth(char ch) {
	if (ch < 256) {
	    return getWidths()[ch];
	}
	char data[] = {ch};
	return charsWidth(data, 0, 1);
    }

    /**
     * Returns the total advance width for showing the specified 
     * <code>String</code> in this <code>Font</code>.  The advance
     * is the distance from the leftmost point to the rightmost point
     * on the string's baseline.  
     * <p>
     * Note that the total advance width returned from this method
     * does not take into account the rendering context.  Therefore, 
     * the anti-aliasing and fractional metrics hints can affect the
     * value of the advance.  When enabling the anti-aliasing and 
     * fractional metrics hints, use 
     * <code>getStringBounds(String, Graphics)</code> 
     * instead of this method.  The advance of a <code>String</code> is
     * not necessarily the sum of the advances of its characters.
     * <p>
     * @param str the <code>String</code> to be measured
     * @return    the advance width of the specified <code>String</code>
     *                  in the <code>Font</code> described by this
     *			<code>FontMetrics</code>.
     * @see       #bytesWidth(byte[], int, int)
     * @see       #charsWidth(char[], int, int)
     * @see       #getStringBounds(String, Graphics)
     */
    public int stringWidth(String str) {
	int len = str.length();
	char data[] = new char[len];
	str.getChars(0, len, data, 0);
	return charsWidth(data, 0, len);
    }

    /**
     * Returns the total advance width for showing the specified array
     * of characters in this <code>Font</code>.  The advance is the
     * distance from the leftmost point to the rightmost point on the
     * string's baseline.  The advance of a <code>String</code>
     * is not necessarily the sum of the advances of its characters.
     * This is equivalent to measuring a <code>String</code> of the
     * characters in the specified range.
     * @param data the array of characters to be measured
     * @param off the start offset of the characters in the array
     * @param len the number of characters to be measured from the array
     * @return    the advance width of the subarray of the specified
     *               <code>char</code> array in the font described by
     *               this <code>FontMetrics</code> object.
     * @see       #charWidth(int)
     * @see       #charWidth(char)
     * @see       #bytesWidth(byte[], int, int)
     * @see       #stringWidth(String)
     */
    public int charsWidth(char data[], int off, int len) {
	return stringWidth(new String(data, off, len));
    }

    /**
     * Returns the total advance width for showing the specified array
     * of bytes in this <code>Font</code>.  The advance is the
     * distance from the leftmost point to the rightmost point on the
     * string's baseline.  The advance of a <code>String</code>
     * is not necessarily the sum of the advances of its characters.  
     * This is equivalent to measuring a <code>String</code> of the
     * characters in the specified range.
     * @param data the array of bytes to be measured
     * @param off the start offset of the bytes in the array
     * @param len the number of bytes to be measured from the array
     * @return    the advance width of the subarray of the specified
     *               <code>byte</code> array in the <code>Font</code> 
     *			described by
     *               this <code>FontMetrics</code> object.
     * @see       #charsWidth(char[], int, int)
     * @see       #stringWidth(String)
     */
    public int bytesWidth(byte data[], int off, int len) {
	return stringWidth(new String(data, 0, off, len));
    }

    /**
     * Gets the advance widths of the first 256 characters in the 
     * <code>Font</code>.  The advance is the
     * distance from the leftmost point to the rightmost point on the
     * character's baseline.  Note that the advance of a
     * <code>String</code> is not necessarily the sum of the advances 
     * of its characters.
     * @return    an array storing the advance widths of the
     *                 characters in the <code>Font</code>
     *                 described by this <code>FontMetrics</code> object.
     */
    public int[] getWidths() {
	int widths[] = new int[256];
	for (char ch = 0 ; ch < 256 ; ch++) {
	    widths[ch] = charWidth(ch);
	}
	return widths;
    }

    /**
     * Checks to see if the <code>Font</code> has uniform line metrics.  A 
     * composite font may consist of several different fonts to cover
     * various character sets.  In such cases, the 
     * <code>FontLineMetrics</code> objects are not uniform.  
     * Different fonts may have a different ascent, descent, metrics and
     * so on.  This information is sometimes necessary for line 
     * measuring and line breaking.
     * @return <code>true</code> if the font has uniform line metrics;
     * <code>false</code> otherwise.
     * @see java.awt.Font#hasUniformLineMetrics()
     */
    public boolean hasUniformLineMetrics() {
        return font.hasUniformLineMetrics();
    }

    /**
     * Returns the {@link LineMetrics} object for the specified
     * <code>String</code> in the specified {@link Graphics} context.
     * @param str the specified <code>String</code>
     * @param context the specified <code>Graphics</code> context
     * @return a <code>LineMetrics</code> object created with the
     * specified <code>String</code> and <code>Graphics</code> context.
     * @see java.awt.Font#getLineMetrics(String, FontRenderContext)
     */
    public LineMetrics getLineMetrics( String str, Graphics context) {
        return font.getLineMetrics(str, myFRC(context));
    }

    /**
     * Returns the {@link LineMetrics} object for the specified
     * <code>String</code> in the specified {@link Graphics} context.
     * @param str the specified <code>String</code>
     * @param beginIndex the initial offset of <code>str</code>
     * @param limit the length of <code>str</code>
     * @param context the specified <code>Graphics</code> context
     * @return a <code>LineMetrics</code> object created with the
     * specified <code>String</code> and <code>Graphics</code> context.
     * @see java.awt.Font#getLineMetrics(String, int, int, FontRenderContext)
     */
    public LineMetrics getLineMetrics( String str,
                                            int beginIndex, int limit,
                                            Graphics context) {
        return font.getLineMetrics(str, beginIndex, limit, myFRC(context));
    }

    /**
     * Returns the {@link LineMetrics} object for the specified
     * character array in the specified {@link Graphics} context.
     * @param chars the specified character array
     * @param beginIndex the initial offset of <code>chars</code>
     * @param limit the length of <code>chars</code>
     * @param context the specified <code>Graphics</code> context
     * @return a <code>LineMetrics</code> object created with the
     * specified character array and <code>Graphics</code> context.
     * @see java.awt.Font#getLineMetrics(char[], int, int, FontRenderContext)
     */
    public LineMetrics getLineMetrics(char [] chars,
                                            int beginIndex, int limit,
                                            Graphics context) {
        return font.getLineMetrics(
                                chars, beginIndex, limit, myFRC(context));
    }

    /**
     * Returns the {@link LineMetrics} object for the specified
     * {@link CharacterIterator} in the specified {@link Graphics} 
     * context.
     * @param ci the specified <code>CharacterIterator</code>
     * @param beginIndex the initial offset in <code>ci</code>
     * @param limit the end index of <code>ci</code>
     * @param context the specified <code>Graphics</code> context
     * @return a <code>LineMetrics</code> object created with the
     * specified arguments.
     * @see java.awt.Font#getLineMetrics(CharacterIterator, int, int, FontRenderContext)
     */
    public LineMetrics getLineMetrics(CharacterIterator ci,
                                            int beginIndex, int limit,
                                            Graphics context) {
        return font.getLineMetrics(ci, beginIndex, limit, myFRC(context));
    }

    /**
     * Returns the bounds of the specified <code>String</code> in the
     * specified <code>Graphics</code> context.  The bounds is used
     * to layout the <code>String</code>.
     * @param str the specified <code>String</code>   
     * @param context the specified <code>Graphics</code> context
     * @return a {@link Rectangle2D} that is the bounding box of the
     * specified <code>String</code> in the specified
     * <code>Graphics</code> context.
     * @see java.awt.Font#getStringBounds(String, FontRenderContext)
     */
    public Rectangle2D getStringBounds( String str, Graphics context) {
        return font.getStringBounds(str, myFRC(context));
    }

    /**
     * Returns the bounds of the specified <code>String</code> in the
     * specified <code>Graphics</code> context.  The bounds is used
     * to layout the <code>String</code>.
     * @param str the specified <code>String</code>
     * @param beginIndex the offset of the beginning of <code>str</code>
     * @param limit the length of <code>str</code>
     * @param context the specified <code>Graphics</code> context
     * @return a <code>Rectangle2D</code> that is the bounding box of the
     * specified <code>String</code> in the specified
     * <code>Graphics</code> context.
     * @see java.awt.Font#getStringBounds(String, int, int, FontRenderContext)
     */
    public Rectangle2D getStringBounds( String str,
                                        int beginIndex, int limit,
                                        Graphics context) {
        return font.getStringBounds(str, beginIndex, limit,
                                        myFRC(context));
    }

   /**
     * Returns the bounds of the specified array of characters
     * in the specified <code>Graphics</code> context.
     * The bounds is used to layout the <code>String</code>
     * created with the specified array of characters,
     * <code>beginIndex</code> and <code>limit</code>.
     * @param chars an array of characters
     * @param beginIndex the initial offset of the array of
     * characters
     * @param limit the length of the array of characters
     * @param context the specified <code>Graphics</code> context
     * @return a <code>Rectangle2D</code> that is the bounding box of the
     * specified character array in the specified
     * <code>Graphics</code> context. 
     * @see java.awt.Font#getStringBounds(char[], int, int, FontRenderContext)
     */ 
    public Rectangle2D getStringBounds( char [] chars,
                                        int beginIndex, int limit,
                                        Graphics context) {
        return font.getStringBounds(chars, beginIndex, limit,
                                        myFRC(context));
    }

   /**
     * Returns the bounds of the characters indexed in the specified
     * <code>CharacterIterator</code> in the
     * specified <code>Graphics</code> context.  
     * @param ci the specified <code>CharacterIterator</code> 
     * @param beginIndex the initial offset in <code>ci</code>
     * @param limit the end index of <code>ci</code>
     * @param context the specified <code>Graphics</code> context
     * @return a <code>Rectangle2D</code> that is the bounding box of the
     * characters indexed in the specified <code>CharacterIterator</code>
     * in the specified <code>Graphics</code> context.
     * @see java.awt.Font#getStringBounds(CharacterIterator, int, int, FontRenderContext)
     */
    public Rectangle2D getStringBounds(CharacterIterator ci,
                                        int beginIndex, int limit,
                                        Graphics context) {
        return font.getStringBounds(ci, beginIndex, limit,
                                        myFRC(context));
    }

    /**
     * Returns the bounds for the character with the maximum bounds
     * in the specified <code>Graphics</code> context.
     * @param context the specified <code>Graphics</code> context
     * @return a <code>Rectangle2D</code> that is the 
     * bounding box for the character with the maximum bounds.
     * @see java.awt.Font#getMaxCharBounds(FontRenderContext)
     */       
    public Rectangle2D getMaxCharBounds(Graphics context) {
        return font.getMaxCharBounds(myFRC(context));
    }

    private FontRenderContext myFRC(Graphics context) {
        if (context instanceof Graphics2D) {
            return ((Graphics2D)context).getFontRenderContext();
        }
        return new FontRenderContext(null, false, false);
    }


    /**
     * Returns a representation of this <code>FontMetrics</code>
     * object's values as a <code>String</code>.
     * @return    a <code>String</code> representation of this 
     * <code>FontMetrics</code> object.
     * @since     JDK1.0.
     */
    public String toString() {
	return getClass().getName() +
	    "[font=" + getFont() +
	    "ascent=" + getAscent() +
	    ", descent=" + getDescent() +
	    ", height=" + getHeight() + "]";
    }

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