RenderManager.java

package jeql.workbench.ui.geomview;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Rectangle2D;
import java.awt.image.*;
import javax.swing.JPanel;
import javax.swing.Timer;


public class RenderManager 
{
	private GeometryViewPanel panel;
  private RendererSwingWorker worker = null;
	private Image image = null;
	private boolean isDirty = true;
	
	private Timer repaintTimer = new Timer(100, new ActionListener() 
	{
		public void actionPerformed(ActionEvent e) {
			if (worker.isRendering()) {
				paintPanel();
				return;
			}
			repaintTimer.stop();
			paintPanel();
		}
	});

	public RenderManager(GeometryViewPanel panel)
	{
		this.panel = panel;
		// start with a short time cycle to give better appearance
		repaintTimer.setInitialDelay(100);
	}

	public void setDirty(boolean isDirty)
	{
		this.isDirty = isDirty;
	}
		
	public void componentResized()
	{
		image = null;
		isDirty = true;
	}
	
	public void render()
	{
		if (image != null && ! isDirty) return;
		
		/*
		 * Clear dirty flag at start of rendering, so that subsequent paints will newly rendered image.
		 * Another way to think of this is that once rendering has been initiated,
		 * from the perspective of the client panel the image is up-to-date 
		 * (although possibly not yet fully rendered)
		 */ 
		isDirty = false;

		repaintTimer.stop();
	
		if (worker != null)
			worker.cancel();
		initImage();
		worker = new RendererSwingWorker(panel.getRenderer(), image);
		worker.start();
		repaintTimer.start();
	}
	
	private void initImage()
	{
		if (image != null) {
			erase(image);
			return;
		}
		image = createPanelImage(panel);
	}
	
  private Image createPanelImage(JPanel panel) {
    return new BufferedImage(panel.getWidth(), panel.getHeight(),
        BufferedImage.TYPE_INT_ARGB);
  }
  
	public void erase(Image image) {
		int width = image.getWidth(null);
		int height = image.getHeight(null);
		
		Graphics2D g = (Graphics2D) image.getGraphics();
		g.setColor(Color.white);

		Rectangle2D.Double r = new Rectangle2D.Double(0, 0, width, height);
		g.fill(r);
	}

	public void copyImage(Graphics g)
	{
    if (image == null) {
      return;
    }
    g.drawImage(image, 0, 0, null);
	}
  
	private void paintPanel()
	{
    copyImage(panel.getGraphics());
	}
}

class RendererSwingWorker extends SwingWorker
{
	private Image image = null;

  private Renderer renderer;
	private boolean isRendering = true;
	
	public RendererSwingWorker(Renderer renderable, Image image)
	{
		this.renderer = renderable;
		this.image = image;
	}
	
  public Object construct()
  {
  	isRendering = true;
		Graphics2D gr = (Graphics2D) image.getGraphics();
    renderer.render(gr);
  	isRendering = false;
    return new Boolean(true);
  }
  
  public boolean isRendering()
  {
  	return isRendering;
  }

  public void cancel()
  {
  	renderer.cancel();
  }

}