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# calculator.cpp Example File
widgets/calculator/calculator.cpp

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        ** This file is part of the documentation of the Qt Toolkit.
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        #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("±"), 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("÷"), operatorColor,
                                          SLOT(multiplicativeOperatorClicked()));
            timesButton = createButton(tr("×"), 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("x²"), 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;

            if (clickedOperator == tr("Sqrt")) {
                if (operand < 0.0) {
                    abortOperation();
                    return;
                }
                result = sqrt(operand);
            } else if (clickedOperator == tr("x²")) {
                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("×")) {
                factorSoFar *= rightOperand;
            } else if (pendingOperator == tr("÷")) {
                if (rightOperand == 0.0)
                    return false;
                factorSoFar /= rightOperand;
            }
            return true;
        }