Canvas canvas = new Canvas(composite, SWT.BORDER);
canvas.addPaintListener(new PaintListener() {
  public void paintControl(PaintEvent e) {
    // draw on e.gc...
  }
});

package org.eclipse.gef.examples.shapes;

//Send questions, comments, bug reports, etc. to the authors:

//Rob Warner (rwarner@interspatial.com)
//Robert Harris (rbrt_harris@yahoo.com)

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

/**
 * This class demonstrates a Canvas
 */
public class SimpleCanvas {
  /**
   * Runs the application
   */
  public void run() {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setText("Canvas Example");
    createContents(shell);
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch()) {
        display.sleep();
      }
    }
    display.dispose();
  }

  /**
   * Creates the main window's contents
   * 
   * @param shell the main window
   */
  private void createContents(Shell shell) {
    shell.setLayout(new GridLayout());

    

    // Create a button on the canvas
    Combo combo = new Combo(shell, SWT.PUSH);
    //combo.setBounds(10, 10, 300, 40);
    combo.setItems(new String[]{"ONE","TWO","FOUR","FIVE"});
    combo.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
 // Create a canvas
    Canvas canvas = new Canvas(shell, SWT.BORDER);
    canvas.setLayoutData(new GridData(GridData.FILL_BOTH));
    // Create a paint handler for the canvas
    canvas.addPaintListener(new PaintListener() {
      public void paintControl(PaintEvent e) {
        // Do some drawing
        Rectangle rect = ((Canvas) e.widget).getClientArea();
        e.gc.setBackground(e.display.getSystemColor(SWT.COLOR_RED));
        e.gc.fillRectangle(rect);
      }
    });
  }

  /**
   * The application entry point
   * 
   * @param args the command line arguments
   */
  public static void main(String[] args) {
    new SimpleCanvas().run();
  }
}