/*
 * DotButtonObj Class
 *
 * Developed for "Rethinking CS101", a project of Lynn Andrea Stein's AP Group.
 * For more information, see <a href="http://www.ai.mit.edu/projects/cs101/">the
 * CS101 homepage</a> or email <las@ai.mit.edu>.
 *
 * Copyright (C) 1997 Massachusetts Institute of Technology.
 * Please do not redistribute without obtaining permission.
 */
package Calculator;

/**
 *  This class is a smart button object that handles the Calculator's
 *  decimal point.  Every ButtonHandler should have one.
 *
 * @author:  Lynn Andrea Stein, las@ai.mit.edu
 * @author:  Luis F. G. Sarmenta, lfgs@mit.edu
 * @version: $$
 *
 * @see Calculator, ButtonHandler, ButtonObj
 */
public class DotButtonObj extends ButtonObj 
{
    /**
     * It turns out that you need the zero button in case the first
     * button after an operator is dot.  In this case, it is
     * convenient to pretend that the zero has been pressed first.  So
     * hold on to that zero ButtonObj! <p>
     *
     * Initialized by constructor, doesn't change.
     */
  private ButtonObj zeroButton;

    /**
     * How to make one: Make a ButtonObj (i.e., my superclass) and
     * also remember that zero button.
     *
     * @param zeroButton  The zero ButtonObj for this calculator.
     * @param gui         The CalcTextGUI to keep track of.
     * @param stateObj    The CalculatorState to keep track of.
     */
  public DotButtonObj( ButtonObj zeroButton, 
		       CalcTextGUI gui,
		       CalculatorState stateObj ) 
  {
    super( gui, stateObj );
    this.zeroButton = zeroButton;
  }
  
    /**
     * This method is called by the ButtonHandler whenever the
     * decimal point button is pressed.  <p>
     *
     * How to handle (my button) being pressed?  If we're already
     * reading a number, add the decimal point to the text and have
     * the state remember.  If we're not reading a number (e.g., we
     * just saw an operation), pretend that the 0 was pressed first.
     */
  public void handleButton() 
  {
    if ( this.stateObj.notReadingNumber() )   // check whether we need 
    {                                         // to pretend that the 0 
      this.zeroButton.handleButton();         // button was pressed.
    }

    // now do dot press -- but only if we haven't already seen a
    // decimal point in this number.
    if ( this.stateObj.noDotYet() ) 
    {
      this.stateObj.justSawDot();
      this.gui.appendText( "." );
    }
  }

}


/*
 * $Log: DotButtonObj.java,v $
 * Revision 1.1.1.1  2002/06/05 21:56:25  root
 * CS101 comes to Olin finally.
 *
 * Revision 1.3  1997/10/30 03:28:35  lfgs
 * Added overview and fixed "* /" commenting typo in code.
 *
 * Revision 1.2  1997/10/24 22:20:41  las
 * Documented all of the code files, but didn't write the user manual (yet).
 *
 */