java - Frame and Canvas grow larger than specified

Question

I have no idea why I am getting an extra-large window, this is making me run hoops to fit my sprites in the game-window. The constructor should make it so all the subcomponents fit into eachother, but it seems like there is some extra padding in the canvas or frame. I am having a tough time figuring out what the culprit is. The size of my frame should NOT be larger than 800x600 (OS decoration not included, talking about the containers).

Panel: java.awt.Rectangle[x=0,y=0,width=810,height=610]
Frame: java.awt.Rectangle[x=0,y=0,width=816,height=638]
Canvas:java.awt.Rectangle[x=0,y=0,width=816,height=638]

As you can see the bounds are larger than I specifed.

The class:

public class GameFrame {
private JFrame frame;
private JPanel panel;
private Canvas canvas;
private BufferStrategy bufferStrategy;
private Graphics2D g;
private int width;
private int height;

public GameFrame(Color bgColor) {
    this.width = GameEngine.GAMEDIMENSION[0]; // 800
    this.height = GameEngine.GAMEDIMENSION[1]; // 600
    this.frame = new JFrame();
    this.panel = (JPanel) frame.getContentPane();
    this.panel.setPreferredSize(new Dimension(width, height));
    this.panel.setLayout(null);
    this.panel.setBackground(bgColor);
    this.canvas = new Canvas();
    this.canvas.setBounds(0, 0, width, height);
    this.canvas.setIgnoreRepaint(true);
    this.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    this.frame.pack();
    this.frame.setResizable(false);
    this.frame.setVisible(true);
    this.panel.add(canvas);
    this.canvas.createBufferStrategy(2);
    this.bufferStrategy = canvas.getBufferStrategy();
    this.g = (Graphics2D) bufferStrategy.getDrawGraphics();
    this.canvas.requestFocus();

}

The main:

public static void main(String[] args) {
    GameFrame gf = new GameFrame(Color.black);
    System.out.println("Panel: " + gf.panel.getBounds());
    System.out.println("Frame: " + gf.frame.getBounds());
    System.out.println("Canvas:" + gf.frame.getBounds());

    for (int R = 0; R < 255; R++) {
        for (int B = 0; B < 255; B++) {
            for (int G = 0; G < 255; G++) {
                gf.g.setColor(Color.black);
                gf.g.fillRect(0, 0, gf.width, gf.height);
                gf.g.setColor(new Color(R, B, G));
                gf.g.fillRect(0, 0, gf.width, gf.height);
                gf.bufferStrategy.show();
            }
        }
    }

}

In the main I try to loop squares just to see the effect.

Answer 1

Swap the pack and setResizable calls, so that pack is the second call.

In the following example, it will write 200x200 on the panel, if you swap the calls it will write 210x210

This is a known "issue"

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestResizeFrame {

    public static void main(String[] args) {
        new TestResizeFrame();
    }

    public TestResizeFrame() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                // Will appear as 200x200, swap them and it will appear as 210x210
                frame.setResizable(false);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g); 
            FontMetrics fm = g.getFontMetrics();
            g.drawString(getWidth() + "x" + getHeight(), 0, fm.getAscent());
        }

    }

}