From 699a1cb9787916b2444468edcc994841f3a6457e Mon Sep 17 00:00:00 2001
From: Itay Grudev <itay@grudev.com>
Date: Wed, 10 Aug 2016 02:50:22 +0100
Subject: Added an example of an application raising the primary instance
 window

This example uses the Qt Calculator example released under the BSD
license. Noted the license difference in the `README.md` and `LICENSE`
files.
---
 examples/calculator/button.cpp     |  73 +++++++
 examples/calculator/button.h       |  68 +++++++
 examples/calculator/calculator.cpp | 406 +++++++++++++++++++++++++++++++++++++
 examples/calculator/calculator.h   | 117 +++++++++++
 examples/calculator/calculator.pro |  11 +
 examples/calculator/main.cpp       |  73 +++++++
 6 files changed, 748 insertions(+)
 create mode 100644 examples/calculator/button.cpp
 create mode 100644 examples/calculator/button.h
 create mode 100644 examples/calculator/calculator.cpp
 create mode 100644 examples/calculator/calculator.h
 create mode 100644 examples/calculator/calculator.pro
 create mode 100644 examples/calculator/main.cpp

(limited to 'examples/calculator')

diff --git a/examples/calculator/button.cpp b/examples/calculator/button.cpp
new file mode 100644
index 0000000..d6cca0a
--- /dev/null
+++ b/examples/calculator/button.cpp
@@ -0,0 +1,73 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtWidgets>
+
+#include "button.h"
+
+//! [0]
+Button::Button(const QString &text, QWidget *parent)
+    : QToolButton(parent)
+{
+    setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred);
+    setText(text);
+}
+//! [0]
+
+//! [1]
+QSize Button::sizeHint() const
+//! [1] //! [2]
+{
+    QSize size = QToolButton::sizeHint();
+    size.rheight() += 20;
+    size.rwidth() = qMax(size.width(), size.height());
+    return size;
+}
+//! [2]
diff --git a/examples/calculator/button.h b/examples/calculator/button.h
new file mode 100644
index 0000000..2c014c7
--- /dev/null
+++ b/examples/calculator/button.h
@@ -0,0 +1,68 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef BUTTON_H
+#define BUTTON_H
+
+#include <QToolButton>
+
+//! [0]
+class Button : public QToolButton
+{
+    Q_OBJECT
+
+public:
+    explicit Button(const QString &text, QWidget *parent = 0);
+
+    QSize sizeHint() const Q_DECL_OVERRIDE;
+};
+//! [0]
+
+#endif
diff --git a/examples/calculator/calculator.cpp b/examples/calculator/calculator.cpp
new file mode 100644
index 0000000..c02b560
--- /dev/null
+++ b/examples/calculator/calculator.cpp
@@ -0,0 +1,406 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtWidgets>
+
+#include <cmath>
+
+#include "button.h"
+#include "calculator.h"
+
+//! [0]
+Calculator::Calculator(QWidget *parent)
+    : QWidget(parent)
+{
+    sumInMemory = 0.0;
+    sumSoFar = 0.0;
+    factorSoFar = 0.0;
+    waitingForOperand = true;
+//! [0]
+
+//! [1]
+    display = new QLineEdit("0");
+//! [1] //! [2]
+    display->setReadOnly(true);
+    display->setAlignment(Qt::AlignRight);
+    display->setMaxLength(15);
+
+    QFont font = display->font();
+    font.setPointSize(font.pointSize() + 8);
+    display->setFont(font);
+//! [2]
+
+//! [4]
+    for (int i = 0; i < NumDigitButtons; ++i) {
+        digitButtons[i] = createButton(QString::number(i), SLOT(digitClicked()));
+    }
+
+    Button *pointButton = createButton(tr("."), SLOT(pointClicked()));
+    Button *changeSignButton = createButton(tr("\302\261"), SLOT(changeSignClicked()));
+
+    Button *backspaceButton = createButton(tr("Backspace"), SLOT(backspaceClicked()));
+    Button *clearButton = createButton(tr("Clear"), SLOT(clear()));
+    Button *clearAllButton = createButton(tr("Clear All"), SLOT(clearAll()));
+
+    Button *clearMemoryButton = createButton(tr("MC"), SLOT(clearMemory()));
+    Button *readMemoryButton = createButton(tr("MR"), SLOT(readMemory()));
+    Button *setMemoryButton = createButton(tr("MS"), SLOT(setMemory()));
+    Button *addToMemoryButton = createButton(tr("M+"), SLOT(addToMemory()));
+
+    Button *divisionButton = createButton(tr("\303\267"), SLOT(multiplicativeOperatorClicked()));
+    Button *timesButton = createButton(tr("\303\227"), SLOT(multiplicativeOperatorClicked()));
+    Button *minusButton = createButton(tr("-"), SLOT(additiveOperatorClicked()));
+    Button *plusButton = createButton(tr("+"), SLOT(additiveOperatorClicked()));
+
+    Button *squareRootButton = createButton(tr("Sqrt"), SLOT(unaryOperatorClicked()));
+    Button *powerButton = createButton(tr("x\302\262"), SLOT(unaryOperatorClicked()));
+    Button *reciprocalButton = createButton(tr("1/x"), SLOT(unaryOperatorClicked()));
+    Button *equalButton = createButton(tr("="), SLOT(equalClicked()));
+//! [4]
+
+//! [5]
+    QGridLayout *mainLayout = new QGridLayout;
+//! [5] //! [6]
+    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"));
+}
+//! [6]
+
+//! [7]
+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));
+}
+//! [7]
+
+//! [8]
+void Calculator::unaryOperatorClicked()
+//! [8] //! [9]
+{
+    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 = std::sqrt(operand);
+    } else if (clickedOperator == tr("x\302\262")) {
+        result = std::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;
+}
+//! [9]
+
+//! [10]
+void Calculator::additiveOperatorClicked()
+//! [10] //! [11]
+{
+    Button *clickedButton = qobject_cast<Button *>(sender());
+    QString clickedOperator = clickedButton->text();
+    double operand = display->text().toDouble();
+
+//! [11] //! [12]
+    if (!pendingMultiplicativeOperator.isEmpty()) {
+//! [12] //! [13]
+        if (!calculate(operand, pendingMultiplicativeOperator)) {
+            abortOperation();
+            return;
+        }
+        display->setText(QString::number(factorSoFar));
+        operand = factorSoFar;
+        factorSoFar = 0.0;
+        pendingMultiplicativeOperator.clear();
+    }
+
+//! [13] //! [14]
+    if (!pendingAdditiveOperator.isEmpty()) {
+//! [14] //! [15]
+        if (!calculate(operand, pendingAdditiveOperator)) {
+            abortOperation();
+            return;
+        }
+        display->setText(QString::number(sumSoFar));
+    } else {
+        sumSoFar = operand;
+    }
+
+//! [15] //! [16]
+    pendingAdditiveOperator = clickedOperator;
+//! [16] //! [17]
+    waitingForOperand = true;
+}
+//! [17]
+
+//! [18]
+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;
+}
+//! [18]
+
+//! [20]
+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;
+}
+//! [20]
+
+//! [22]
+void Calculator::pointClicked()
+{
+    if (waitingForOperand)
+        display->setText("0");
+    if (!display->text().contains('.'))
+        display->setText(display->text() + tr("."));
+    waitingForOperand = false;
+}
+//! [22]
+
+//! [24]
+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);
+}
+//! [24]
+
+//! [26]
+void Calculator::backspaceClicked()
+{
+    if (waitingForOperand)
+        return;
+
+    QString text = display->text();
+    text.chop(1);
+    if (text.isEmpty()) {
+        text = "0";
+        waitingForOperand = true;
+    }
+    display->setText(text);
+}
+//! [26]
+
+//! [28]
+void Calculator::clear()
+{
+    if (waitingForOperand)
+        return;
+
+    display->setText("0");
+    waitingForOperand = true;
+}
+//! [28]
+
+//! [30]
+void Calculator::clearAll()
+{
+    sumSoFar = 0.0;
+    factorSoFar = 0.0;
+    pendingAdditiveOperator.clear();
+    pendingMultiplicativeOperator.clear();
+    display->setText("0");
+    waitingForOperand = true;
+}
+//! [30]
+
+//! [32]
+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();
+}
+//! [32]
+//! [34]
+Button *Calculator::createButton(const QString &text, const char *member)
+{
+    Button *button = new Button(text);
+    connect(button, SIGNAL(clicked()), this, member);
+    return button;
+}
+//! [34]
+
+//! [36]
+void Calculator::abortOperation()
+{
+    clearAll();
+    display->setText(tr("####"));
+}
+//! [36]
+
+//! [38]
+bool Calculator::calculate(double rightOperand, const QString &pendingOperator)
+{
+    if (pendingOperator == tr("+")) {
+        sumSoFar += rightOperand;
+    } else if (pendingOperator == tr("-")) {
+        sumSoFar -= rightOperand;
+    } else if (pendingOperator == tr("\303\227")) {
+        factorSoFar *= rightOperand;
+    } else if (pendingOperator == tr("\303\267")) {
+        if (rightOperand == 0.0)
+            return false;
+        factorSoFar /= rightOperand;
+    }
+    return true;
+}
+//! [38]
diff --git a/examples/calculator/calculator.h b/examples/calculator/calculator.h
new file mode 100644
index 0000000..250a2f3
--- /dev/null
+++ b/examples/calculator/calculator.h
@@ -0,0 +1,117 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef CALCULATOR_H
+#define CALCULATOR_H
+
+#include <QWidget>
+
+QT_BEGIN_NAMESPACE
+class QLineEdit;
+QT_END_NAMESPACE
+class Button;
+
+//! [0]
+class Calculator : public QWidget
+{
+    Q_OBJECT
+
+public:
+    Calculator(QWidget *parent = 0);
+
+private slots:
+    void digitClicked();
+    void unaryOperatorClicked();
+    void additiveOperatorClicked();
+    void multiplicativeOperatorClicked();
+    void equalClicked();
+    void pointClicked();
+    void changeSignClicked();
+    void backspaceClicked();
+    void clear();
+    void clearAll();
+    void clearMemory();
+    void readMemory();
+    void setMemory();
+    void addToMemory();
+//! [0]
+
+//! [1]
+private:
+//! [1] //! [2]
+    Button *createButton(const QString &text, const char *member);
+    void abortOperation();
+    bool calculate(double rightOperand, const QString &pendingOperator);
+//! [2]
+
+//! [3]
+    double sumInMemory;
+//! [3] //! [4]
+    double sumSoFar;
+//! [4] //! [5]
+    double factorSoFar;
+//! [5] //! [6]
+    QString pendingAdditiveOperator;
+//! [6] //! [7]
+    QString pendingMultiplicativeOperator;
+//! [7] //! [8]
+    bool waitingForOperand;
+//! [8]
+
+//! [9]
+    QLineEdit *display;
+//! [9] //! [10]
+
+    enum { NumDigitButtons = 10 };
+    Button *digitButtons[NumDigitButtons];
+};
+//! [10]
+
+#endif
diff --git a/examples/calculator/calculator.pro b/examples/calculator/calculator.pro
new file mode 100644
index 0000000..8f13260
--- /dev/null
+++ b/examples/calculator/calculator.pro
@@ -0,0 +1,11 @@
+QT += widgets
+
+HEADERS = button.h \
+    calculator.h
+SOURCES = button.cpp \
+    calculator.cpp \
+    main.cpp
+
+# Single Application implementation
+include(../../singleapplication.pri)
+DEFINES += QAPPLICATION_CLASS=QApplication
diff --git a/examples/calculator/main.cpp b/examples/calculator/main.cpp
new file mode 100644
index 0000000..7d8708b
--- /dev/null
+++ b/examples/calculator/main.cpp
@@ -0,0 +1,73 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QApplication>
+
+#include <SingleApplication.h>
+
+#include "calculator.h"
+
+int main(int argc, char *argv[])
+{
+    SingleApplication app(argc, argv);
+
+    Calculator calc;
+
+    QObject::connect(
+        &app,
+        &SingleApplication::instanceStarted,
+        &calc,
+        &Calculator::raise
+    );
+
+    calc.show();
+
+    return app.exec();
+}
-- 
cgit v1.2.1