Graphics2D.drawString() fails with Font derived from rotated + scaled AffineTransform

[Daniel Gredler]

Hi all,

I've run into a bug [1] in the drawing of strings via
Graphics2D.drawString(), when used with a Font derived from a rotated +
scaled AffineTransform. If the AffineTransform scaling is small, the text
draws correctly. But if the scale is too large, the text does not draw. [3]

It looks like it's an effect of the OutlineTextRenderer.THRESHHOLD; text
larger than this threshold is sent to the OutlineTextRenderer and fails to
draw. The fix [2] seems to be to apply the position translation
transformation *after* the text outline shape is created, rather than
passing it into TextLayout.getOutline(). However, I do not know if this is
the correct fix, or if it is just a workaround to a deeper issue in
TextLayout.getOutline(), which in theory might need to wait to apply the
provided translation until after the layout path has had a chance to map to
user space.

Can someone familiar with this code comment on whether the proposed fix is
the correct fix, or whether deeper surgery is needed in
TextLayout.getOutline()?

My other small worry with the current fix [2] is that it creates an extra
copy of the Shape object, so it's going to allocate a bit more memory than
the current implementation. Not sure if there's a better way to update the
Shape in-place.

Take care,

Daniel

---

[1] Oracle internal review ID 9077538, no public bug ID yet
[2]
https://github.com/openjdk/jdk/compare/master...gredler:jdk:draw-string-bug
[3]
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;

/**
 * <p>The "TEST 2" text does not draw. NOTE: Reducing the AffineTransform
scale
 * from 12 to 10 seems to allow it to draw?!?
 *
 * <p>Oracle internal review ID : 9077538
 */
public class DrawStringTest {

    public static void main(String[] args) throws Exception {

        AffineTransform at = AffineTransform.getRotateInstance(3 * Math.PI
/ 2);
        at.scale(12, 12);

        Font font1 = new Font("SansSerif", Font.PLAIN, 10);
        Font font2 = font1.deriveFont(at);

        BufferedImage image = new BufferedImage(500, 500,
BufferedImage.TYPE_BYTE_GRAY);
        Graphics2D g2d = image.createGraphics();
        g2d.setColor(Color.WHITE);
        g2d.fillRect(0, 0, image.getWidth(), image.getHeight());
        g2d.setColor(Color.BLACK);
        g2d.setFont(font1);
        g2d.drawString("TEST 1", 200, 400); // draws text
        g2d.setFont(font2);
        g2d.drawString("TEST 2", 200, 400); // does not draw text
        g2d.dispose();

        ImageIO.write(image, "png", new File("test.png"));
    }

}
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