calculator_display.lzx

<library>
    <resource name="calc_display" src="./resources/display.png"/>

    <!-- The calculator display -->
    <class name="calcDisplay" resource="calc_display" x="20" y="31" oninit="this.start()">
        <!-- the text in the display -->
        <text name="screen" height="30" width="165" font="displayText" fontsize="25" y="5" x="5">
            0
        </text>

        <method name="start">
            this.valueX = 0;
            this.lastInput = 'none';
            this.oldValue = false;
            this.allOperators = new Array( '+', '-', '/', '*' );
            this.operator = '+';
            this.screen.setAttribute('text',  this.valueX.toString() );
        </method>
        
        <method name="clear">
            this.start();
        </method>

        <!-- handles the push of a button -->
        <method name="inputDigit" args="buttonObj">
        
            var val = buttonObj.buttonText.text;

            // weed out any non-numbers (e.g. operators, clear button)
            if ( isInArray( val, this.allOperators ) ) {
                var theOperator = val;
                this.inputOperator( theOperator );
                return;
            } else if ( val == 'C' ) {
                this.start();
                return;
            } else if ( val == '.' ) {
                this.addDecimalPoint();
                return;
            } else if ( val == '+/-' ) {
                this.negative();
                return;
            } else if ( val == '=' ) {
                this.equals();
                return;
            }

            var displ = this.screen.text;
            if ( ( displ == '0' ) && ( val == '0' ) ) {
                return;
            }

            if ( ( this.lastInput == 'none' ) 
                || ( this.lastInput == 'operator' ) ) {
                // clear display and rewrite
                this.screen.setAttribute('text',  val );    
            } else if ( this.lastInput == 'digit' ) {
                this.screen.setAttribute('text',  displ + val );
            } else if ( this.lastInput == 'equals' ) {
                this.clear();
                this.screen.setAttribute('text',  val );
            }
            this.lastInput = 'digit';
        
        </method>

        <method name="inputOperator" args="operator">
            if ( this.lastInput == 'digit' ) {
                this.execute( this.screen.text );
            }
            this.valueX = this.screen.text;
            this.operator = operator;
            this.lastInput = 'operator';
        </method>

        <method name="equals">
            if (this.lastInput != 'equals' ) {
                this.oldValue = this.screen.text;
                this.lastInput = 'equals';
                this.execute( this.oldValue );
            } else {
                this.lastInput = 'equals';
                this.execute( this.oldValue );
            }
        </method>

        <method name="execute" args="val">
            this.valueX -= 0;
            var valFromDisp = val - 0;
            if ( this.valueX == 0 ) return;

            if ( this.operator == '+' ) {
                val = this.valueX + valFromDisp;
            } else if ( this.operator == '-' ) {
                val = this.valueX - valFromDisp;
            } else if ( this.operator == '*' ) {
                val = this.valueX * valFromDisp;
            } else if ( this.operator == '/' ) {
                val = this.valueX / valFromDisp;
            }
            valFromDisp = val;
            this.screen.setAttribute('text',  valFromDisp.toString() );
            this.valueX = this.screen.text;
        </method>

        <method name="isThereDecimal">
        
            var disp = this.screen.text;
            var isDecimal = false;
            for ( var i=0; i<disp.length; i++ ) {
                if ( disp.charAt( i ) == '.' ) {
                    return true;
                }
            }
            return false;
        
        </method>
        
        <method name="addDecimalPoint">
            if ( ( this.lastInput == 'none' ) 
                || ( this.lastInput == 'operator' ) ) {
                if ( !this.isThereDecimal() ) {
                    this.screen.setAttribute('text',  "0." );
                }
            } else if ( this.lastInput == 'digit' ) {
                if ( !this.isThereDecimal() ) {
                    var newText = this.screen.text;
                    newText += ".";
                    this.screen.setAttribute('text',  newText );
                }
            } else if ( this.lastInput == 'equals' ) {
                this.clear(); 
                this.screen.setAttribute('text',  '0.' );
            }
            this.lastInput = 'digit';
        </method>
        

        <method name="negative">
            if ( ( this.lastInput == 'digit' ) ||
                ( this.lastInput == 'equals' ) ) {
                var newDisp = ( this.screen.text - 0 ) * -1;
                this.screen.setAttribute('text',  newDisp.toString() ); 
            } else {
                clear();
            }            
        </method>
    </class>
</library>
<!-- * X_LZ_COPYRIGHT_BEGIN ***************************************************
* Copyright 2001-2007,2011 Laszlo Systems, Inc.  All Rights Reserved.         *
* Use is subject to license terms.                                            *
* X_LZ_COPYRIGHT_END ****************************************************** -->

Cross References

Resources

Name	Source	Image
calc_display	./resources/display.png

Classes

• <class name="calcDisplay">