content: /********************************************************************************
   * The contents of this file are subject to the GNU General Public License      *
   * (GPL) Version 2 or later (the "License"); you may not use this file except   *
   * in compliance with the License. You may obtain a copy of the License at      *
   * http://www.gnu.org/copyleft/gpl.html                                         *
   *                                                                              *
   * Software distributed under the License is distributed on an "AS IS" basis,   *
   * without warranty of any kind, either expressed or implied. See the License   *
   * for the specific language governing rights and limitations under the         *
   * License.                                                                     *
   *                                                                              *
   * This file was originally developed as part of the software suite that        *
   * supports the book "The Elements of Computing Systems" by Nisan and Schocken, *
   * MIT Press 2005. If you modify the contents of this file, please document and *
   * mark your changes clearly, for the benefit of others.                        *
   ********************************************************************************/
  
  package builtInChips;
  
  import java.awt.*;
  import Hack.Gates.*;
  import Hack.Utilities.*;
  import SimulatorsGUI.*;
  
  /**
  /* A 512X256 screen, implemented with 8K registers, each register represents 16 pixels.
   */
  public class Screen extends BuiltInGateWithGUI {
  
      // The gui
      private ScreenComponent gui;
  
      // The memory array
      private short[] values;
  
      /**
       * Constructs a new Screen.
       */
      public Screen() {
          values = new short[Definitions.SCREEN_SIZE_IN_WORDS];
          if (GatesManager.getInstance().isChipsGUIEnabled()) {
              gui = new ScreenComponent();
              gui.setLocation(4,2);
          }
      }
  
      protected void clockUp() {
          short in = inputPins[0].get(); // 16 bit input
          short load = inputPins[1].get(); // load bit
          short address = inputPins[2].get(); // 13 bit address
          if (load == 1) {
              values[address] = in;
              if (gui != null)
                  gui.setValueAt(address, in);
          }
      }
  
      protected void reCompute() {
          short address = inputPins[2].get(); // 13 bit address
          outputPins[0].set(values[address]);
      }
  
      protected void clockDown() {
          reCompute();
      }
  
      public Component getGUIComponent() {
          return gui;
      }
  
      // updates the given value
      private void updateValue(int address, short value) {
          values[address] = value;
          if (gui != null)
              gui.setValueAt(address, value);
          reCompute();
          evalParent();
      }
  
      public short getValueAt(int index) throws GateException {
          checkIndex(index);
          return values[index];
      }
  
      // checks the given index. If illegal throws GateException.
      private void checkIndex(int index) throws GateException {
          if (index < 0 || index >= values.length)
              throw new GateException("Illegal index");
      }
  
      public void setValueAt(int index, short value) throws GateException {
          checkIndex(index);
          updateValue(index, value);
      }
  }
  