ADDITIONAL SYSTEM INFORMATION :
Windows 10
OpenJDK 11.0.8 and OpenJDK 15.0.1

A DESCRIPTION OF THE PROBLEM :
When drawing a String in an undecorated dialog with a transparent background with the font family 'Segoe UI' the String looks distorted (quasi bold) in comparison to the String drawn in a normal frame.
This seems to be a problem with the text antialiasing. This worked correctly in OpenJDK 11.0.2 and is broken at least since OpenJDK 11.0.4.

REGRESSION : Last worked in version 11

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached source code example to see the problem

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The String rendered in the window opened when pressing the button looks the same as the String rendered under the button.
ACTUAL -
The String rendered in the window opened when pressing the button looks different from the String rendered under the button (looks quasi bold).

---------- BEGIN SOURCE ----------
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JWindow;
import javax.swing.WindowConstants;
import java.awt.Button;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;

public final class AwtSample {
  private static final Font FONT_SEGOE_UI = new Font("Segoe UI", Font.PLAIN, 13);

  public static void main(String[] args) {
    JFrame frame = new JFrame("Sample");
    frame.setSize(500, 200);
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

    Button button = new Button("Click me");
    button.setBackground(Color.WHITE);
    button.addActionListener(__ -> {
      JWindow dialog = new JWindow();
      dialog.setSize(110, 110);
      dialog.setLocationRelativeTo(button);
      dialog.setBackground(new Color(255, 255, 255, 0));

      Component canvas = createCanvas();
      dialog.add(canvas);

      dialog.setVisible(true);
    });

    Container contentPane = frame.getContentPane();
    contentPane.setBackground(Color.WHITE);
    contentPane.setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS));
    contentPane.add(button);
    contentPane.add(createCanvas());

    frame.setVisible(true);
  }

  private static Component createCanvas() {
    Component canvas = new Component() {
      @Override
      public void paint(Graphics g) {
        ((Graphics2D) g).setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_LCD_HRGB);
        super.paint(g);
        g.setFont(FONT_SEGOE_UI);
        g.drawString("Test", 12, 50);
      }
    };
    canvas.setSize(100, 100);
    return canvas;
  }
}
---------- END SOURCE ----------

FREQUENCY : always