calculator.cpp Example File
^{widgets/calculator/calculator.cpp}

    /****************************************************************************
    **
    ** Copyright (C) 2005-2006 Trolltech ASA. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
    **
    ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 as published by the Free Software Foundation
    ** and appearing in the file LICENSE.GPL included in the packaging of
    ** this file.  Please review the following information to ensure GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
    ** http://www.trolltech.com/products/qt/licensing.html or contact the
    ** sales department at sales@trolltech.com.
    **
    ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
    **
    ****************************************************************************/

    #include <QtGui>

    #include <math.h>

    #include "button.h"
    #include "calculator.h"

    Calculator::Calculator(QWidget *parent)
        : QDialog(parent)
    {
        sumInMemory = 0.0;
        sumSoFar = 0.0;
        factorSoFar = 0.0;
        waitingForOperand = true;

        display = new QLineEdit("0");
        display->setReadOnly(true);
        display->setAlignment(Qt::AlignRight);
        display->setMaxLength(15);
        display->installEventFilter(this);

        QFont font = display->font();
        font.setPointSize(font.pointSize() + 8);
        display->setFont(font);

        QColor digitColor(150, 205, 205);
        QColor backspaceColor(225, 185, 135);
        QColor memoryColor(100, 155, 155);
        QColor operatorColor(155, 175, 195);

        for (int i = 0; i < NumDigitButtons; ++i) {
            digitButtons[i] = createButton(QString::number(i), digitColor,
                                           SLOT(digitClicked()));
        }

        pointButton = createButton(tr("."), digitColor, SLOT(pointClicked()));
        changeSignButton = createButton(tr("\261"), digitColor, SLOT(changeSignClicked()));

        backspaceButton = createButton(tr("Backspace"), backspaceColor,
                                       SLOT(backspaceClicked()));
        clearButton = createButton(tr("Clear"), backspaceColor, SLOT(clear()));
        clearAllButton = createButton(tr("Clear All"), backspaceColor.light(120),
                                      SLOT(clearAll()));

        clearMemoryButton = createButton(tr("MC"), memoryColor,
                                         SLOT(clearMemory()));
        readMemoryButton = createButton(tr("MR"), memoryColor, SLOT(readMemory()));
        setMemoryButton = createButton(tr("MS"), memoryColor, SLOT(setMemory()));
        addToMemoryButton = createButton(tr("M+"), memoryColor,
                                         SLOT(addToMemory()));

        divisionButton = createButton(tr("\367"), operatorColor,
                                      SLOT(multiplicativeOperatorClicked()));
        timesButton = createButton(tr("\327"), operatorColor,
                                   SLOT(multiplicativeOperatorClicked()));
        minusButton = createButton(tr("-"), operatorColor,
                                   SLOT(additiveOperatorClicked()));
        plusButton = createButton(tr("+"), operatorColor,
                                  SLOT(additiveOperatorClicked()));

        squareRootButton = createButton(tr("Sqrt"), operatorColor,
                                        SLOT(unaryOperatorClicked()));
        powerButton = createButton(tr("x\262"), operatorColor,
                                   SLOT(unaryOperatorClicked()));
        reciprocalButton = createButton(tr("1/x"), operatorColor,
                                        SLOT(unaryOperatorClicked()));
        equalButton = createButton(tr("="), operatorColor.light(120),
                                   SLOT(equalClicked()));

        QGridLayout *mainLayout = new QGridLayout;
        mainLayout->setSizeConstraint(QLayout::SetFixedSize);

        mainLayout->addWidget(display, 0, 0, 1, 6);
        mainLayout->addWidget(backspaceButton, 1, 0, 1, 2);
        mainLayout->addWidget(clearButton, 1, 2, 1, 2);
        mainLayout->addWidget(clearAllButton, 1, 4, 1, 2);

        mainLayout->addWidget(clearMemoryButton, 2, 0);
        mainLayout->addWidget(readMemoryButton, 3, 0);
        mainLayout->addWidget(setMemoryButton, 4, 0);
        mainLayout->addWidget(addToMemoryButton, 5, 0);

        for (int i = 1; i < NumDigitButtons; ++i) {
            int row = ((9 - i) / 3) + 2;
            int column = ((i - 1) % 3) + 1;
            mainLayout->addWidget(digitButtons[i], row, column);
        }

        mainLayout->addWidget(digitButtons[0], 5, 1);
        mainLayout->addWidget(pointButton, 5, 2);
        mainLayout->addWidget(changeSignButton, 5, 3);

        mainLayout->addWidget(divisionButton, 2, 4);
        mainLayout->addWidget(timesButton, 3, 4);
        mainLayout->addWidget(minusButton, 4, 4);
        mainLayout->addWidget(plusButton, 5, 4);

        mainLayout->addWidget(squareRootButton, 2, 5);
        mainLayout->addWidget(powerButton, 3, 5);
        mainLayout->addWidget(reciprocalButton, 4, 5);
        mainLayout->addWidget(equalButton, 5, 5);
        setLayout(mainLayout);

        setWindowTitle(tr("Calculator"));
    }

    bool Calculator::eventFilter(QObject *target, QEvent *event)
    {
        if (target == display) {
            if (event->type() == QEvent::MouseButtonPress
                    || event->type() == QEvent::MouseButtonDblClick
                    || event->type() == QEvent::MouseButtonRelease
                    || event->type() == QEvent::ContextMenu) {
                QMouseEvent *mouseEvent = static_cast<QMouseEvent *>(event);
                if (mouseEvent->buttons() & Qt::LeftButton) {
                    QPalette newPalette = palette();
                    newPalette.setColor(QPalette::Base,
                                        display->palette().color(QPalette::Text));
                    newPalette.setColor(QPalette::Text,
                                        display->palette().color(QPalette::Base));
                    display->setPalette(newPalette);
                } else {
                    display->setPalette(palette());
                }
                return true;
            }
        }
        return QDialog::eventFilter(target, event);
    }

    void Calculator::digitClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        int digitValue = clickedButton->text().toInt();
        if (display->text() == "0" && digitValue == 0.0)
            return;

        if (waitingForOperand) {
            display->clear();
            waitingForOperand = false;
        }
        display->setText(display->text() + QString::number(digitValue));
    }

    void Calculator::unaryOperatorClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        QString clickedOperator = clickedButton->text();
        double operand = display->text().toDouble();
        double result = 0.0;

        if (clickedOperator == tr("Sqrt")) {
            if (operand < 0.0) {
                abortOperation();
                return;
            }
            result = sqrt(operand);
        } else if (clickedOperator == tr("x\262")) {
            result = pow(operand, 2.0);
        } else if (clickedOperator == tr("1/x")) {
            if (operand == 0.0) {
                abortOperation();
                return;
            }
            result = 1.0 / operand;
        }
        display->setText(QString::number(result));
        waitingForOperand = true;
    }

    void Calculator::additiveOperatorClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        QString clickedOperator = clickedButton->text();
        double operand = display->text().toDouble();

        if (!pendingMultiplicativeOperator.isEmpty()) {
            if (!calculate(operand, pendingMultiplicativeOperator)) {
                abortOperation();
                return;
            }
            display->setText(QString::number(factorSoFar));
            operand = factorSoFar;
            factorSoFar = 0.0;
            pendingMultiplicativeOperator.clear();
        }

        if (!pendingAdditiveOperator.isEmpty()) {
            if (!calculate(operand, pendingAdditiveOperator)) {
                abortOperation();
                return;
            }
            display->setText(QString::number(sumSoFar));
        } else {
            sumSoFar = operand;
        }

        pendingAdditiveOperator = clickedOperator;
        waitingForOperand = true;
    }

    void Calculator::multiplicativeOperatorClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        QString clickedOperator = clickedButton->text();
        double operand = display->text().toDouble();

        if (!pendingMultiplicativeOperator.isEmpty()) {
            if (!calculate(operand, pendingMultiplicativeOperator)) {
                abortOperation();
                return;
            }
            display->setText(QString::number(factorSoFar));
        } else {
            factorSoFar = operand;
        }

        pendingMultiplicativeOperator = clickedOperator;
        waitingForOperand = true;
    }

    void Calculator::equalClicked()
    {
        double operand = display->text().toDouble();

        if (!pendingMultiplicativeOperator.isEmpty()) {
            if (!calculate(operand, pendingMultiplicativeOperator)) {
                abortOperation();
                return;
            }
            operand = factorSoFar;
            factorSoFar = 0.0;
            pendingMultiplicativeOperator.clear();
        }
        if (!pendingAdditiveOperator.isEmpty()) {
            if (!calculate(operand, pendingAdditiveOperator)) {
                abortOperation();
                return;
            }
            pendingAdditiveOperator.clear();
        } else {
            sumSoFar = operand;
        }

        display->setText(QString::number(sumSoFar));
        sumSoFar = 0.0;
        waitingForOperand = true;
    }

    void Calculator::pointClicked()
    {
        if (waitingForOperand)
            display->setText("0");
        if (!display->text().contains("."))
            display->setText(display->text() + tr("."));
        waitingForOperand = false;
    }

    void Calculator::changeSignClicked()
    {
        QString text = display->text();
        double value = text.toDouble();

        if (value > 0.0) {
            text.prepend(tr("-"));
        } else if (value < 0.0) {
            text.remove(0, 1);
        }
        display->setText(text);
    }

    void Calculator::backspaceClicked()
    {
        if (waitingForOperand)
            return;

        QString text = display->text();
        text.chop(1);
        if (text.isEmpty()) {
            text = "0";
            waitingForOperand = true;
        }
        display->setText(text);
    }

    void Calculator::clear()
    {
        if (waitingForOperand)
            return;

        display->setText("0");
        waitingForOperand = true;
    }

    void Calculator::clearAll()
    {
        sumSoFar = 0.0;
        factorSoFar = 0.0;
        pendingAdditiveOperator.clear();
        pendingMultiplicativeOperator.clear();
        display->setText("0");
        waitingForOperand = true;
    }

    void Calculator::clearMemory()
    {
        sumInMemory = 0.0;
    }

    void Calculator::readMemory()
    {
        display->setText(QString::number(sumInMemory));
        waitingForOperand = true;
    }

    void Calculator::setMemory()
    {
        equalClicked();
        sumInMemory = display->text().toDouble();
    }

    void Calculator::addToMemory()
    {
        equalClicked();
        sumInMemory += display->text().toDouble();
    }

    Button *Calculator::createButton(const QString &text, const QColor &color,
                                     const char *member)
    {
        Button *button = new Button(text, color);
        connect(button, SIGNAL(clicked()), this, member);
        return button;
    }

    void Calculator::abortOperation()
    {
        clearAll();
        display->setText(tr("####"));
    }

    bool Calculator::calculate(double rightOperand, const QString &pendingOperator)
    {
        if (pendingOperator == tr("+")) {
            sumSoFar += rightOperand;
        } else if (pendingOperator == tr("-")) {
            sumSoFar -= rightOperand;
        } else if (pendingOperator == tr("\327")) {
            factorSoFar *= rightOperand;
        } else if (pendingOperator == tr("\367")) {
            if (rightOperand == 0.0)
                return false;
            factorSoFar /= rightOperand;
        }
        return true;
    }