Drawing Demo First Extension

This is the first extension. It adds a few things but there is more to come. (It also adds a bug, because this version flickers when you are drawing. I left the bug in, and we can fix it in the next version.)

Doodle is taken from the DoodlePad example in Exploring Java, by Patrick Niemeyer and Joshua Peck, first edition copyright 1996 by O'Reilly and Associates. It lets you draw with the mouse. Use the buttons to clear the picture, or to change the drawing color or line thickness.

You cannot run applets

/** Extended from the DoodlePad example in Exploring Java,
 * by Patrick Niemeyer and Joshua Peck,
 * First edition Copyright 1996 O'Reilly Publishing.  */

import java.awt.*;
import java.applet.*;

public class Doodle1 extends Applet {

  DrawingPad1 dPad;

  Button
         clearButton,
         biggerButton, smallerButton,
         undoButton;

  Checkbox
	 writeHButton, writeVButton,
         redButton, yellowButton, greenButton, blueButton;

  CheckboxGroup
	 writeHVGroup = new CheckboxGroup (),
         colorsGroup = new CheckboxGroup ();

/** To run as an application,
 * construct it and show it in a frame.
 * This must be a static (class not instance) method,
 * because the instance won't exist until we construct it here.
 * When run as an applet,
 * the browser provides the frame,
 * and calls the constructor and init methods. */

  public static void main (String []argv) {

      Doodle1 cd = new Doodle1 ();

      Frame ff = new Frame ("Doodle");
      ff.setBounds (100, 100, 600, 300);

      ff.add (cd);
      cd.init ();

      ff.show ();
  }

/** Make everything,
 * a drawing surface and some controls. */

  public void init () {

/* A big central drawing area and some controls on the edges */

     setLayout (new BorderLayout ());

     add ("Center", dPad = new DrawingPad1 ());

     Panel np = new Panel ();
     np.setLayout (new GridLayout (0, 1));

     np.add (clearButton = new Button ("Clear"));

/* Note set/getCurrent deprecated now set/getSelectedCheckbox */

     add ("West", np);

     Panel sp = new Panel ();
     sp.setLayout (new GridLayout (0, 1));

     sp.add (biggerButton = new Button ("bigger"));
     sp.add (smallerButton = new Button ("smaller"));

     sp.add (writeHButton = new Checkbox ("Write Horiz"));
     writeHButton.setCheckboxGroup (writeHVGroup);

     sp.add (writeVButton = new Checkbox ("Write Vert"));
     writeVButton.setCheckboxGroup (writeHVGroup);

     writeHVGroup.setCurrent (writeHButton);

     sp.add (yellowButton = new Checkbox ("yellow"));
     yellowButton.setCheckboxGroup (colorsGroup);

     sp.add (redButton = new Checkbox ("red"));
     redButton.setCheckboxGroup (colorsGroup);

     sp.add (greenButton = new Checkbox ("green"));
     greenButton.setCheckboxGroup (colorsGroup);

     sp.add (blueButton = new Checkbox ("blue"));
     blueButton.setCheckboxGroup (colorsGroup);

     colorsGroup.setCurrent (blueButton);

     add ("East", sp);
  }

/** Handle the button and say we did */

  public boolean action (Event e, Object o) {
     if (e.target == clearButton) dPad.clear ();
     if (e.target == biggerButton) dPad.bigger ();
     if (e.target == smallerButton) dPad.smaller ();

     if ((e.target == redButton)
      && redButton.getState ()) dPad.setPaint (Color.red);
     if ((e.target == yellowButton)
      && yellowButton.getState ()) dPad.setPaint (Color.yellow);
     if ((e.target == greenButton)
      && greenButton.getState ()) dPad.setPaint (Color.green);
     if ((e.target == blueButton)
      && blueButton.getState ()) dPad.setPaint (Color.blue);

      if ((e.target == writeHButton)
       && writeHButton.getState ()) dPad.setHV (0);

      if ((e.target == writeVButton)
       && writeVButton.getState ()) dPad.setHV (1);

/* Must requestFocus to get key strokes */

     dPad.requestFocus ();

     return true;
  }

}

class DrawingPad1 extends Canvas {

  Image di;
  Graphics dg;
  int xpos, ypos, xold, yold;

  int hv = 0;

  DrawingPad1 () {
      setBackground (Color.white);
      setForeground (Color.blue);
  }

  public void setPaint (Color fg) { dg.setColor (fg); }

  public void setHV (int m) { hv = m; }


  public boolean mouseDown (Event e, int x, int y) {

     xold = x; yold = y;

     return true;
  }


  public boolean mouseDrag (Event e, int x, int y) {
     if (dg == null) return false;

/* Add another line segment to the offscreen image. */

     xpos = x; ypos = y;
     dg.drawLine (xold, yold, xpos, ypos);
     xold=xpos; yold=ypos;

/* We need a repaint */

     repaint ();
     return true;
  }

/** Prevent pre-clear since we fill whole space anyway */

  public void update (Graphics g) { paint (g); }

  public void paint (Graphics g) {
     if (di == null) {
         di = createImage (size ().width, size ().height);
         dg = di.getGraphics ();
     }

/* Everything from the accumulated offscreen image */

     g.drawImage (di, 0, 0, null);

     g.setColor (Color.black);
     g.drawRect (0, 0, size ().width-1, size ().height-1);
  }

  public void clear () {
     di.getGraphics ().clearRect (0, 0, size ().width, size ().height);
     repaint ();
  }

/* There is no keyClick just Down and Up.
 * "Keypress:C:NN"
 * C is String [1] for the key character if defined else "?".
 * NN is String [2 or more] for the numeric key code,
 * high numbers > 1000 are control keys. */

  public boolean keyDown (Event evt, int key) {
     if (dg == null) return false;

     if (key > 1000) return false;

 // System.out.println ("Keypress:"+String.valueOf ((char)key)+":"+String.valueOf (key));

     String ks = String.valueOf ((char)key);

     FontMetrics fm = dg.getFontMetrics ();

     dg.drawString (ks, xold, yold);

/* Advance either across or down */

     if (0 == hv)
         xold += fm.stringWidth (ks);
     else
         yold += fm.getHeight ();

     repaint ();
     return true;
  }

/** Must requestFocus to get key strokes */

  public synchronized boolean mouseEnter (Event me, int x, int y) {
     requestFocus ();
     return true;
  }

/** This **always** gives a newFont with getSize as requested,
 *  but they may be displayed as the same size anyway.
 *  and NOT change size on our Unix box,
 *  although fine on a Windows/NT box. */

  public void bigger () { changeFont (2); }

  public void smaller () { changeFont (-2); }

  void changeFont (int delta) {

     Component pcomp = getParent ();

     Font oldFont = getFont ();

     if ((null == oldFont)
      && (null != pcomp))
         oldFont = pcomp.getFont ();

     if (null == oldFont)
         return;

     Font newFont = new Font
          (oldFont.getName (),
           oldFont.getStyle (),
           oldFont.getSize () + delta);

/* Existing dg won't see it so tell them */

     setFont (newFont);
     dg.setFont (newFont);
   }

}

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Legalities

Except as otherwise noted, this work is Copyright (C) 2000 by Morris Hirsch. In particular, Doodle is taken from the DoodlePad example in Exploring Java, by Patrick Niemeyer and Joshua Peck, first edition copyright 1996 by O'Reilly and Associates. All rights reserved, except as granted here.

Redistribution and use in source and binary forms, with or without modification, for any purpose, are permitted, except as may be restricted by original copyright holders, provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer, in the documentation, and/or other materials provided with the distribution.

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