(C++) QGraphicsSimpleTextItemExample3

 

 

QGraphicsSimpleTextItem example 3: use tab to change focus is a QGraphicsSimpleTextItem example that displays multiple QGraphicsSimpleTextItems with their coordinats as text. These items are movable and selectable. By pressing tab, focus will be set to a random item.

 

• View a screenshot of 'QGraphicsSimpleTextItemExample3' (png)
• Download the Qt Creator project 'QGraphicsSimpleTextItemExample3' (zip)
• Download a Windows executable of 'QGraphicsSimpleTextItemExample3' (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++98

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: ./CppQGraphicsSimpleTextItemExample3/CppQGraphicsSimpleTextItemExample3.pro

 

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exists(../../DesktopApplication.pri) {   include(../../DesktopApplication.pri) } !exists(../../DesktopApplication.pri) {   QT       += core gui   greaterThan(QT_MAJOR_VERSION, 4): QT += widgets   win32 {     greaterThan(QT_MAJOR_VERSION, 4): QT += svg   }   TEMPLATE = app   CONFIG(debug, debug|release) {     message(Debug mode)   }   CONFIG(release, debug|release) {     message(Release mode)     DEFINES += NDEBUG NTRACE_BILDERBIKKEL   }   QMAKE_CXXFLAGS += -std=c++1y -Wall -Wextra -Weffc++   unix {     QMAKE_CXXFLAGS += -Werror   } } exists(../../Libraries/Boost.pri) {   include(../../Libraries/Boost.pri) } !exists(../../Libraries/Boost.pri) {   INCLUDEPATH += \     ../../Libraries/boost_1_55_0 } SOURCES += \     qtmain.cpp \     qtwidget.cpp \     qttextitem.cpp HEADERS += \     qtwidget.h \     qttextitem.h

 

 

 

 

 

./CppQGraphicsSimpleTextItemExample3/qtmain.cpp

 

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#pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QApplication> #include <QDesktopWidget> #include "qtwidget.h" #pragma GCC diagnostic pop int main(int argc, char *argv[]) {   QApplication a(argc, argv);   QtWidget w;   {     //Resize the dialog and put it in the screen center     w.setGeometry(0,0,600,400);     const QRect screen = QApplication::desktop()->screenGeometry();     w.move( screen.center() - w.rect().center() );   }   w.show();   return a.exec(); }

 

 

 

 

 

./CppQGraphicsSimpleTextItemExample3/qttextitem.h

 

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#ifndef QTTEXTITEM_H #define QTTEXTITEM_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QGraphicsSimpleTextItem> #pragma GCC diagnostic pop struct QtTextItem : public QGraphicsSimpleTextItem {   QtTextItem(QGraphicsItem *parent = 0);   void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget); }; #endif // QTTEXTITEM_H

 

 

 

 

 

./CppQGraphicsSimpleTextItemExample3/qttextitem.cpp

 

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#include "qttextitem.h" #include <cassert> #include <sstream> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #pragma GCC diagnostic pop QtTextItem::QtTextItem(QGraphicsItem *parent) : QGraphicsSimpleTextItem(parent) {   this->setFlags(       QGraphicsItem::ItemIsFocusable     | QGraphicsItem::ItemIsMovable     | QGraphicsItem::ItemIsSelectable); } void QtTextItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) {   std::stringstream s;   s << "(" << static_cast<int>(this->pos().x()) << "," << static_cast<int>(this->pos().y()) << ")";   this->setText(s.str().c_str());   QGraphicsSimpleTextItem::paint(painter,option,widget); }

 

 

 

 

 

./CppQGraphicsSimpleTextItemExample3/qtwidget.h

 

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#ifndef QTWIDGET_H #define QTWIDGET_H #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <QGraphicsView> #pragma GCC diagnostic pop ///The widget holding the items struct QtWidget : public QGraphicsView {   QtWidget(QWidget *parent = 0);   ///Respond to a key press   void keyPressEvent(QKeyEvent *event); }; #endif // QTWIDGET_H

 

 

 

 

 

./CppQGraphicsSimpleTextItemExample3/qtwidget.cpp

 

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#include "qtwidget.h" #include <cassert> #include <cmath> #include <iostream> #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Weffc++" #pragma GCC diagnostic ignored "-Wunused-local-typedefs" #include <boost/math/constants/constants.hpp> #include <QGraphicsScene> #include <QKeyEvent> #include "qttextitem.h" #pragma GCC diagnostic pop QtWidget::QtWidget(QWidget *parent)   : QGraphicsView(new QGraphicsScene,parent) {   const int n_items = 16;   for (int i=0; i!=n_items; ++i)   {     const double angle       = boost::math::constants::two_pi<double>()       * (static_cast<double>(i+0) / static_cast<double>(n_items))     ;     const double ray = 150.0;     const double x =  std::sin(angle) * ray;     const double y = -std::cos(angle) * ray;     QtTextItem * const item = new QtTextItem;     item->setPos(x,y);     scene()->addItem(item);   } } void QtWidget::keyPressEvent(QKeyEvent *event) {   switch (event->key())   {     case Qt::Key_Tab:     {       //Let existing item lose focus       if (QGraphicsItem * const item = scene()->focusItem())       {         //Really lose focus         item->setEnabled(false);         item->clearFocus();         item->setEnabled(true);       }       //Let a random item receive focus       const QList<QGraphicsItem *> items = this->items();       items.at( std::rand() % items.size() )->setFocus();     }     break;   }   //Let QGraphicsView do the rest...   QGraphicsView::keyPressEvent(event); }