I have a large sized JPanel within a JScrollPane, and in this JPanel need to render LOTS of stuff. To speed up rendering I am using the Clip Rect (specified by the graphics object method getClipBounds()) to render only the things needed. I noticed the width of the returned rectangle seems somewhat unpredictable during a scrolling drag event (eg when a user drags the scroll bar). Here's a short snippet demonstrating the behavior - run, and start a repaint by resizing the window or dragging the scroll bar and notice the difference in printed out values. A similar behavior occurs when I animate the scrolling with a Timer

import javax.swing.*;
import java.awt.*;
 
public class ScrollDemo extends JFrame{
 
	public ScrollDemo(){
		super();
		ScrollPanel scPanel = new ScrollPanel();
		scPanel.setPreferredSize(new Dimension(5000,200));
		JScrollPane scroller = new JScrollPane(scPanel);
		scroller.setPreferredSize(new Dimension(500,200));
		getContentPane().add(scroller);
		pack();
		setVisible(true);
	}
 
	private class ScrollPanel extends JPanel{
		/**
		 * Paints the component and prints out the values of the 
		 * Clip Rect width every time it paints.
		 */
		@Override public void paintComponent(Graphics g){
			super.paintComponent(g);
			Rectangle rect = g.getClipBounds();
			System.out.println(rect.width);
		}
	}
	public static void main(String[] args){
		new ScrollDemo();
	}
}

It would be ideal if the width of the clip bounds actually gave the values I expected, but its not and I'm curious as to why and if there is a workaround to the issue.