Initial Commit

.gitignore

+# This file is used to ignore files which are generated
+# ----------------------------------------------------------------------------
+
+*~
+*.autosave
+*.a
+*.core
+*.moc
+*.o
+*.obj
+*.orig
+*.rej
+*.so
+*.so.*
+*_pch.h.cpp
+*_resource.rc
+*.qm
+.#*
+*.*#
+core
+!core/
+tags
+.DS_Store
+.directory
+*.debug
+Makefile*
+*.prl
+*.app
+moc_*.cpp
+ui_*.h
+qrc_*.cpp
+Thumbs.db
+*.res
+*.rc
+/.qmake.cache
+/.qmake.stash
+
+# qtcreator generated files
+*.pro.user*
+
+# xemacs temporary files
+*.flc
+
+# Vim temporary files
+.*.swp
+
+# Visual Studio generated files
+*.ib_pdb_index
+*.idb
+*.ilk
+*.pdb
+*.sln
+*.suo
+*.vcproj
+*vcproj.*.*.user
+*.ncb
+*.sdf
+*.opensdf
+*.vcxproj
+*vcxproj.*
+
+# MinGW generated files
+*.Debug
+*.Release
+
+# Python byte code
+*.pyc
+
+# Binaries
+# --------
+*.dll
+*.exe
+
+# build directory
+build*/
+
+#vscode
+.vscode/
+
+# not using Qt Creator
+CMakeLists.txt.user
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CMakeLists.txt

+cmake_minimum_required(VERSION 3.5)
+
+add_subdirectory(Counter)
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Counter/CMakeLists.txt

+cmake_minimum_required(VERSION 3.5)
+
+project(Counter VERSION 0.1 LANGUAGES CXX)
+
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+set(CMAKE_AUTOUIC ON)
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
+find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)
+
+set(PROJECT_SOURCES
+        main.cpp
+        mainwindow.cpp
+        mainwindow.h
+        myLineEdit.cpp
+        myLineEdit.h
+)
+
+if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
+    qt_add_executable(Counter
+        MANUAL_FINALIZATION
+        ${PROJECT_SOURCES}
+    )
+# Define target properties for Android with Qt 6 as:
+#    set_property(TARGET Counter APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
+#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
+# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
+else()
+    if(ANDROID)
+        add_library(Counter SHARED
+            ${PROJECT_SOURCES}
+        )
+# Define properties for Android with Qt 5 after find_package() calls as:
+#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
+    else()
+        add_executable(Counter
+            ${PROJECT_SOURCES}
+        )
+    endif()
+endif()
+
+target_link_libraries(Counter PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)
+
+set_target_properties(Counter PROPERTIES
+    MACOSX_BUNDLE_GUI_IDENTIFIER my.example.com
+    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
+    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
+    MACOSX_BUNDLE TRUE
+    WIN32_EXECUTABLE TRUE
+)
+
+if(QT_VERSION_MAJOR EQUAL 6)
+    qt_finalize_executable(Counter)
+endif()

Counter/main.cpp

+#include "mainwindow.h"
+
+#include <QApplication>
+
+int main(int argc, char *argv[])
+{
+    QApplication a(argc, argv);
+    MainWindow w;
+    w.show();
+    return a.exec();
+}

Counter/mainwindow.cpp

+#include <QPushButton>
+#include <QLineEdit>
+#include <QBoxLayout>
+
+#include "myLineEdit.h"
+
+#include "mainwindow.h"
+
+MainWindow::MainWindow(QWidget *parent)
+    : QMainWindow(parent)
+{
+//general
+    setWindowTitle("Counter");
+// Layout
+    QBoxLayout *layout = new QBoxLayout(QBoxLayout::Direction::TopToBottom);
+    QWidget *widget = new QWidget;
+    widget->setLayout(layout);
+    this->setCentralWidget(widget); // special for MainWindow
+
+// Increment Button
+    QPushButton *plusButton = new QPushButton("Increase");
+
+    layout->addWidget(plusButton);
+    connect(plusButton, SIGNAL(clicked()), this, SLOT(onPlusButton()));
+
+// Derived Display
+    myLineEdit *mydisplay = new myLineEdit("0"); //Constructors are inherited
+    mydisplay->setReadOnly(true);
+    mydisplay->setAlignment(Qt::AlignCenter);
+    QFont font1 = mydisplay->font();
+    font1.setPointSize(font1.pointSize() + 8);
+    mydisplay->setFont(font1);
+
+    layout->addWidget(mydisplay);
+    connect(this, SIGNAL(counterChanged(int)), mydisplay, SLOT(updateFromInt(int)));
+
+// Decrement Button
+    QPushButton *minusButton = new QPushButton("Decrease");
+
+    layout->addWidget(minusButton);
+    connect(minusButton, SIGNAL(clicked()), this, SLOT(onMinusButton()));
+
+// Q Display
+    QLineEdit *qdisplay = new QLineEdit("0");
+    qdisplay->setReadOnly(true);
+    qdisplay->setAlignment(Qt::AlignCenter);
+    QFont font2 = qdisplay->font();
+    font2.setPointSize(font2.pointSize() + 8);
+    qdisplay->setFont(font2);
+
+    layout->addWidget(qdisplay);
+    connect(this, SIGNAL(counterChanged(const QString&)), qdisplay, SLOT(setText(const QString&)));
+}
+
+void MainWindow::onPlusButton()
+{
+    ++Counter;
+
+    //For derived display
+    emit(counterChanged(Counter));
+
+    //For Q display
+    QString str = QString(std::to_string(Counter).c_str());
+    QString& strRef = str;
+    emit(counterChanged(strRef));
+}
+
+void MainWindow::onMinusButton()
+{
+    --Counter;
+
+    //For derived display
+    emit(counterChanged(Counter));
+
+    //For Q display
+    QString str = QString(std::to_string(Counter).c_str());
+    emit(counterChanged(str));
+}
+
+MainWindow::~MainWindow()
+{
+}
+

Counter/mainwindow.h

+#ifndef MAINWINDOW_H
+#define MAINWINDOW_H
+
+#include <QMainWindow>
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+private:
+    int Counter = 0;
+
+public:
+    MainWindow(QWidget *parent = nullptr);
+    ~MainWindow();
+
+private slots:
+    void onPlusButton();
+    void onMinusButton();
+
+signals:
+    void counterChanged(int);
+    void counterChanged(const QString &);
+};
+#endif // MAINWINDOW_H

Counter/myLineEdit.cpp

+#include "myLineEdit.h"
+
+void myLineEdit::updateFromInt(int num)
+{
+    QString str = QString(std::to_string(num).c_str());
+    this->setText(str);
+}
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Counter/myLineEdit.h

+#ifndef MYLINEEDIT_H
+#define MYLINEEDIT_H
+
+
+#include <QLineEdit>
+
+class myLineEdit : public QLineEdit
+{
+    Q_OBJECT
+
+public:
+    using QLineEdit::QLineEdit; // inherit constructors of QLineEdit
+
+public slots:
+    void updateFromInt(int);
+};
+
+#endif // MYLINEEDIT_H
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