GlyphVector bounds and kerning, ligatures

[Steve Lovelace]

Shouldn't GlyphVector report positions/bounds for glyphs which reflect kerning and ligatures, i.e., shouldn't it yield metrics which correspond to what is actually rendered by Graphics2D.drawString() or TextLayout.draw()? Below is a little app which will throw up a frame showing a string rendered in black, the GlyphVector's logicalBounds in yellow fill, and the logicalBounds of each glyph in red. You can see the bounding rectangles creep as kerns and ligatures are encountered. I had to pick a font that actually does kerning and ligatures (DejaVu Sans) because on my system (JDK1.6-u13 on Ubuntu 9.04) the default fonts do not. Attached is a screen shot of the frame produced.

 
package examples;

import java.util.*;
import java.awt.*;
import java.awt.font.*;
import java.awt.geom.*;
import static java.awt.font.TextAttribute.*;
import javax.swing.*;


public class GlyphVectorBounds {

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel p = new XPanel();
        p.setBackground(Color.WHITE);
        p.setOpaque(true);
        f.setContentPane(p);
        f.setSize(750, 150);
        f.setVisible(true);
    }

    static class XPanel extends JPanel {
        String text = "Tiffany's Terrific Toffee Taffy";
        Font baseFont = new Font("DejaVu Sans", Font.PLAIN, 48);
        Map attr= new HashMap();
        {
            attr.put(KERNING, KERNING_ON);
            attr.put(LIGATURES, LIGATURES_ON);
        }
        AffineTransform trans = AffineTransform.getTranslateInstance(20, 70);

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setTransform(trans);
            Font font = baseFont.deriveFont(attr);
            g2.setFont(font);
            FontRenderContext frc = g2.getFontRenderContext();
            GlyphVector gv = font.createGlyphVector(frc, text);
            Rectangle2D vb = gv.getLogicalBounds();
            g2.setColor(Color.YELLOW);
            g2.fill(vb);
            g2.setColor(Color.RED);
            for (int i=0; i<gv.getNumGlyphs(); i++) {
                Shape gb = gv.getGlyphLogicalBounds(i);
                g2.draw(gb);
            }
            g2.setColor(Color.BLACK);
            g2.drawString(text, 0, 0);
        }
    }

}   

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