src/java.desktop/windows/classes/sun/awt/windows/WFontMetrics.java

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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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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package sun.awt.windows;

import java.awt.*;
import java.util.Hashtable;

/**
 * A font metrics object for a WServer font.
 *
 * @author Jim Graham
 */
@SuppressWarnings("serial") // JDK-implementation class
final class WFontMetrics extends FontMetrics {

    static {
        initIDs();
    }

    /**
     * The widths of the first 256 characters.
     */
    int widths[];

    /**
     * The standard ascent of the font.  This is the logical height
     * above the baseline for the Alphanumeric characters and should
     * be used for determining line spacing.  Note, however, that some
     * characters in the font may extend above this height.
     */
    int ascent;

    /**
     * The standard descent of the font.  This is the logical height
     * below the baseline for the Alphanumeric characters and should
     * be used for determining line spacing.  Note, however, that some
     * characters in the font may extend below this height.
     */
    int descent;

    /**
     * The standard leading for the font.  This 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.
     */
    int leading;

    /**
     * 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 ascent+descent+leading.  There is no
     * guarantee that lines of text spaced at this distance will be
     * disjoint; such lines may overlap if some characters overshoot
     * the standard ascent and descent metrics.
     */
    int height;

    /**
     * The maximum ascent for all characters in this font.  No character
     * will extend further above the baseline than this metric.
     */
    int maxAscent;

    /**
     * The maximum descent for all characters in this font.  No character
     * will descend further below the baseline than this metric.
     */
    int maxDescent;

    /**
     * The maximum possible height of a line of text in this font.
     * Adjacent lines of text spaced this distance apart will be
     * guaranteed not to overlap.  Note, however, that many paragraphs
     * that contain ordinary alphanumeric text may look too widely
     * spaced if this metric is used to determine line spacing.  The
     * height field should be preferred unless the text in a given
     * line contains particularly tall characters.
     */
    int maxHeight;

    /**
     * The maximum advance width of any character in this font.
     */
    int maxAdvance;

    /**
     * Calculate the metrics from the given WServer and font.
     */
    public WFontMetrics(Font font) {
        super(font);
        init();
    }

    /**
     * Get leading
     */
    @Override
    public int getLeading() {
        return leading;
    }

    /**
     * Get ascent.
     */
    @Override
    public int getAscent() {
        return ascent;
    }

    /**
     * Get descent
     */
    @Override
    public int getDescent() {
        return descent;
    }

    /**
     * Get height
     */
    @Override
    public int getHeight() {
        return height;
    }

    /**
     * Get maxAscent
     */
    @Override
    public int getMaxAscent() {
        return maxAscent;
    }

    /**
     * Get maxDescent
     */
    @Override
    public int getMaxDescent() {
        return maxDescent;
    }

    /**
     * Get maxAdvance
     */
    @Override
    public int getMaxAdvance() {
        return maxAdvance;
    }

    /**
     * Return the width of the specified string in this Font.
     */
    @Override
    public native int stringWidth(String str);

    /**
     * Return the width of the specified char[] in this Font.
     */
    @Override
    public native int charsWidth(char data[], int off, int len);

    /**
     * Return the width of the specified byte[] in this Font.
     */
    @Override
    public native int bytesWidth(byte data[], int off, int len);

    /**
     * Get the widths of the first 256 characters in the font.
     */
    @Override
    public int[] getWidths() {
        return widths;
    }

    native void init();

    static Hashtable<Font, FontMetrics> table = new Hashtable<>();

    static FontMetrics getFontMetrics(Font font) {
        FontMetrics fm = table.get(font);
        if (fm == null) {
            table.put(font, fm = new WFontMetrics(font));
        }
        return fm;
    }

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