(C++) QtExample17

 

 

This Qt example shows how to modify a QLabel to make it clickable, resulting in a traffic light, like this screenshot (png).

 

• Download the Qt Project of 'QtExample17' (zip)

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 15.04 (vivid)

IDE(s):

• Qt Creator 3.1.1

Project type:

• GUI application

C++ standard:

• C++11

Compiler(s):

• G++ 4.9.2

Libraries used:

• Qt: version 5.4.1 (32 bit)
• STL: GNU ISO C++ Library, version 4.9.2

 

 

 

 

 

Qt project file: ./CppQtExample17/CppQtExample17.pro

 

---

exists(../../DesktopApplication.pri) {   include(../../DesktopApplication.pri) } !exists(../../DesktopApplication.pri) {   QT += core gui   greaterThan(QT_MAJOR_VERSION, 4): QT += widgets   TEMPLATE = app   CONFIG(debug, debug|release) {     message(Debug mode)   }   CONFIG(release, debug|release) {     message(Release mode)     DEFINES += NDEBUG NTRACE_BILDERBIKKEL   }   QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra   unix {     QMAKE_CXXFLAGS += -Werror   } } exists(../../Libraries/Boost.pri) {   include(../../Libraries/Boost.pri) } !exists(../../Libraries/Boost.pri) {   win32 {     INCLUDEPATH += \       ../../../Projects/Libraries/boost_1_55_0   } } SOURCES += main.cpp SOURCES += \     trafficlightdialog.cpp \     image.cpp HEADERS  += \     trafficlightdialog.h \     image.h FORMS    += trafficlightdialog.ui RESOURCES += resources.qrc

 

 

 

 

 

./CppQtExample17/image.h

 

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#ifndef IMAGE_H #define IMAGE_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QColor> #include <QLabel> #include <QObject> #pragma GCC diagnostic pop struct QColor; struct QMouseEvent; class Image : public QLabel {   Q_OBJECT public:     Image(const QString& filename);     void mousePressEvent( QMouseEvent * e); signals:     void onClick(); }; #endif // IMAGE_H

 

 

 

 

 

./CppQtExample17/image.cpp

 

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#include "image.h" #include <cassert> #include <iostream> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QBitmap> #include <QColor> #include <QImage> #include <QPixmap> #include <QMouseEvent> #pragma GCC diagnostic pop Image::Image(const QString& filename) {   //MouseTracking must be set to true, to make Image clickable   this->setMouseTracking(true);   //Set the image   QPixmap pixmap(filename);   std::clog << "Using pixmap file '" << filename.toStdString() << "'\n";   assert(!pixmap.isNull());   //Set transparency (white, in this example)   const QBitmap mask = pixmap.createMaskFromColor(QColor(255,255,255,0).rgb());   pixmap.setMask(mask);   this->setPixmap(pixmap); } void Image::mousePressEvent( QMouseEvent *) {   std::clog << "emitting onClick()\n";   emit onClick(); }

 

 

 

 

 

./CppQtExample17/main.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QApplication> #include "trafficlightdialog.h" #pragma GCC diagnostic pop int main(int argc, char *argv[]) {   QApplication a(argc, argv);   TrafficLightDialog w;   w.show();   return a.exec(); }

 

 

 

 

 

./CppQtExample17/trafficlightdialog.h

 

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#ifndef TRAFFICLIGHTDIALOG_H #define TRAFFICLIGHTDIALOG_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <boost/shared_ptr.hpp> #include <QDialog> #pragma GCC diagnostic pop struct Image; namespace Ui {   class TrafficLightDialog; } class TrafficLightDialog : public QDialog {   Q_OBJECT public:   explicit TrafficLightDialog(QWidget *parent = 0);   TrafficLightDialog(const TrafficLightDialog&) = delete;   TrafficLightDialog& operator=(const TrafficLightDialog&) = delete;   ~TrafficLightDialog(); private:   Ui::TrafficLightDialog *ui;   //Images on the screen   boost::shared_ptr<Image> m_red;   boost::shared_ptr<Image> m_orange;   boost::shared_ptr<Image> m_green;   //Read-only off-screen images   boost::shared_ptr<const Image> m_red_on;   boost::shared_ptr<const Image> m_orange_on;   boost::shared_ptr<const Image> m_green_on;   boost::shared_ptr<const Image> m_red_off;   boost::shared_ptr<const Image> m_orange_off;   boost::shared_ptr<const Image> m_green_off; private slots:   void onRedClicked();   void onOrangeClicked();   void onGreenClicked(); }; #endif // TRAFFICLIGHTDIALOG_H

 

 

 

 

 

./CppQtExample17/trafficlightdialog.cpp

 

---

#include "trafficlightdialog.h" #include <iostream> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QVBoxLayout> #include "ui_trafficlightdialog.h" #include "image.h" #pragma GCC diagnostic pop TrafficLightDialog::TrafficLightDialog(QWidget *parent) :     QDialog(parent),     ui(new Ui::TrafficLightDialog),     m_red(new Image(":/images/RedOff64x64.png")),     m_orange(new Image(":/images/OrangeOff64x64.png")),     m_green(new Image(":/images/GreenOff64x64.png")),     m_red_on(new Image(":/images/Red64x64.png")),     m_orange_on(new Image(":/images/Orange64x64.png")),     m_green_on(new Image(":/images/Green64x64.png")),     m_red_off(new Image(":/images/RedOff64x64.png")),     m_orange_off(new Image(":/images/OrangeOff64x64.png")),     m_green_off(new Image(":/images/GreenOff64x64.png"))     //m_red_on(false),     //m_orange_on(false),     //m_green_on(false) {   ui->setupUi(this);   m_red->setAlignment(Qt::AlignHCenter);   m_orange->setAlignment(Qt::AlignHCenter);   m_green->setAlignment(Qt::AlignHCenter);   QVBoxLayout * layout = new QVBoxLayout(this);   layout->addWidget(m_red.get());   layout->addWidget(m_orange.get());   layout->addWidget(m_green.get());   m_red->connect(m_red.get(),SIGNAL(onClick()),this,SLOT(onRedClicked()));   m_red->connect(m_orange.get(),SIGNAL(onClick()),this,SLOT(onOrangeClicked()));   m_red->connect(m_green.get(),SIGNAL(onClick()),this,SLOT(onGreenClicked())); } TrafficLightDialog::~TrafficLightDialog() {   delete ui; } void TrafficLightDialog::onRedClicked() {   std::clog << "Red clicked\n";   m_red->setPixmap(*m_red_on->pixmap());   m_orange->setPixmap(*m_orange_off->pixmap());   m_green->setPixmap(*m_green_off->pixmap()); } void TrafficLightDialog::onOrangeClicked() {   std::clog << "Orange clicked\n";   m_red->setPixmap(*m_red_off->pixmap());   m_orange->setPixmap(*m_orange_on->pixmap());   m_green->setPixmap(*m_green_off->pixmap()); } void TrafficLightDialog::onGreenClicked() {   std::clog << "Green clicked\n";   m_red->setPixmap(*m_red_off->pixmap());   m_orange->setPixmap(*m_orange_off->pixmap());   m_green->setPixmap(*m_green_on->pixmap()); }