/* InteractiveTurtleApplet.java -- Interactive Turtle using the com.lrdev.turtle package. ** ** Copyright (C) 1997-2003 Eric Laroche. All rights reserved. ** ** @author Eric Laroche ** @version 1.2 @(#)$Id: InteractiveTurtleApplet.java,v 1.2 2003/02/16 12:40:56 laroche Exp $ ** ** This program is free software; ** you can redistribute it and/or modify it. ** ** This program is distributed in the hope that it will be useful, ** but WITHOUT ANY WARRANTY; without even the implied warranty of ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. ** */ // note: no wildcard imports // Use the AWT based graphics Turtle package. import com.lrdev.turtle.PersistentTurtle; import java.applet.Applet; import java.awt.Color; import java.awt.Event; import java.awt.Graphics; import java.awt.Rectangle; /** InteractiveTurtleApplet: Interactive Turtle using the com.lrdev.turtle package. * * @author Eric Laroche * @version 1.2 @(#)$Id: InteractiveTurtleApplet.java,v 1.2 2003/02/16 12:40:56 laroche Exp $ */ public class InteractiveTurtleApplet extends Applet { /** Version. */ private final static String m_version = "Version: 1.2 @(#)$Id: InteractiveTurtleApplet.java,v 1.2 2003/02/16 12:40:56 laroche Exp $"; /** Author. */ private final static String m_author = "Author: Eric Laroche "; /** Applet usage. */ private final static String[][] m_usage = {}; // ---------------- /** Associated Turtle. */ private PersistentTurtle m_turtle = new PersistentTurtle(); /** Default Turtle advance length. */ private final static double m_defaultLength = 16; /** Turtle advance length. */ private double m_length = m_defaultLength; /** Default Turtle heading change. */ private final static double m_defaultOmega = Math.PI / 2; /** Turtle heading change. */ private double m_omega = m_defaultOmega; /** Last command. */ private int m_lastCommand = 'h'; // home /** User interface update flag. */ private boolean m_uiNeedsUpdate = false; // ---------------- /** Called by the browser. * Returns info on this applet. * * Overwrites Applet.getAppletInfo. */ public String getAppletInfo() { return m_version + "\n" + m_author + "\n\n" + "interactive usage:\n" + interactiveUsage(); } /** Called by the browser. * Returns info on the parameters of this applet. * * Overwrites Applet.getParameterInfo. */ public String[][] getParameterInfo() { return m_usage; } /** Constructor. */ public InteractiveTurtleApplet() { // NOTE: must postpone getParameter() calls to init() } /** Called after the constructor and before start(). * Sets the background color and reads in the applet parameters. * * Overwrites Applet.init. */ public void init() { // white background, black foreground setBackground(Color.white); setForeground(Color.black); } /** Called by the browser. * * Overwrites Applet.start. */ public void start() { } /* Called by the browser. * * Overwrites Applet.stop. */ public void stop() { } /** Called by the browser. * * Overwrites Applet.destroy. */ public void destroy() { } /** Repaint the component if needed. */ protected void repaintIfNeeded() { if (m_uiNeedsUpdate) { repaint(); } } /** Paint the component. * * Overwrites Component.paint. */ public void paint(Graphics graphics) { m_uiNeedsUpdate = false; // get drawing box Rectangle b = bounds(); // 2 pixel border int border = 2; b.width -= 2 * border; b.height -= 2 * border; b.x += border; b.y += border; // check if the box is large enough if (b.width < 0 || b.height < 0) { // we're too small return; } // have the thing centered at all times m_turtle.center(); m_turtle.paint(graphics, b); } /** Handle keyboard input. * * Overwrites Component.keyDown. */ public boolean keyDown(Event event, int key) { boolean handled = doCommand(key); repaintIfNeeded(); return handled; } /** Command interpreter. * * @return command handled * *

* doCommand() does not call repaint() to indicate GUI needs an * update, since doCommand() is allowed to be called by * non-UI-handling threads [in that case, that thread and paint() * would have to be synchronized]. Instead, m_uiNeedsUpdate is * updated. Note however that m_uiNeedsUpdate is not a * (synchronized) monitor, it's only used synchronous. */ protected boolean doCommand(int command) { if (command == 'D') { // reDo command = m_lastCommand; } m_lastCommand = command; switch (command) { case 'u' : // penUp m_turtle.penup(); return true; // event handled case 'd' : // penDown m_turtle.pendown(); return true; // event handled case 'f' : // Forward m_turtle.forward(m_length); m_uiNeedsUpdate = true; // GUI needs update return true; // event handled case 'F' : // Forward less m_turtle.forward(m_length / 4); m_uiNeedsUpdate = true; // GUI needs update return true; // event handled case 'b' : // Back m_turtle.back(m_length); m_uiNeedsUpdate = true; // GUI needs update return true; // event handled case 'B' : // Back less m_turtle.back(m_length / 4); m_uiNeedsUpdate = true; // GUI needs update return true; // event handled case 'l' : // Left m_turtle.left(m_omega); return true; // event handled case 'L' : // Left less m_turtle.left(m_omega / 4); return true; // event handled case 'r' : // Right m_turtle.right(m_omega); return true; // event handled case 'R' : // Right less m_turtle.right(m_omega / 4); return true; // event handled case 'h' : // Home m_turtle.home(); m_uiNeedsUpdate = true; // GUI needs update return true; // event handled // not supported: // setxy // setx // sety // setheading // towards case 'S' : // reSet m_turtle.reset(); // reset current turtle parameters m_length = m_defaultLength; m_omega = m_defaultOmega; m_uiNeedsUpdate = true; // GUI needs update return true; // event handled case 'U' : // Undo m_turtle.undo(); m_uiNeedsUpdate = true; // GUI needs update return true; // event handled case 'D' : // reDo // done above. // we shouldn't get here. // leave the case in, to catch reused labels. break; case '+' : // increase length m_length += m_defaultLength; return true; // event handled case '-' : // decrease length m_length -= m_defaultLength; if (m_length < 1) { m_length = 1; } return true; // event handled case '*' : // double length m_length *= 2; return true; // event handled case '/' : // half length m_length /= 2; if (m_length < 1) { m_length = 1; } return true; // event handled } return false; // event not handled } /** Return interactive usage. */ protected static String interactiveUsage() { return "u: penUp" + "\n" + "d: penDown" + "\n" + "f: Forward" + "\n" + "F: Forward less" + "\n" + "b: Back" + "\n" + "B: Back less" + "\n" + "l: Left" + "\n" + "L: Left less" + "\n" + "r: Right" + "\n" + "R: Right less" + "\n" + "h: Home" + "\n" + "S: reSet" + "\n" + "U: Undo" + "\n" + "D: reDo" + "\n" + "+: increase length" + "\n" + "-: decrease length" + "\n" + "*: double length" + "\n" + "/: half length" + "\n" + "\n"; } }