QGraphicsPixmapItem example 2: clickable pixmap is a QGraphicsPixmapItem example. This example shows how to put multiple movable QGraphicsPixmapItems on screen and let them respond to mouse clicks using a boost::signal.

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: ./CppQGraphicsPixmapItemExample2/CppQGraphicsPixmapItemExample2.pro


exists (../../DesktopApplication.pri) {

  include(../../DesktopApplication.pri)

}

!exists (../../DesktopApplication.pri) {

  QT += core printsupport

  QT += gui

  greaterThan(QT_MAJOR_VERSION, 4): QT += widgets svg

  CONFIG   += console

  CONFIG   -= app_bundle

  TEMPLATE = app

  CONFIG(release, debug|release) {

    DEFINES += NDEBUG NTRACE_BILDERBIKKEL

  }

  QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++

  unix {

    QMAKE_CXXFLAGS += -Werror

  }

}



exists(../../Libraries/Boost.pri) {

  include(../../Libraries/Boost.pri)

}

!exists(../../Libraries/Boost.pri) {

  win32 {

    INCLUDEPATH += \

      ../../Libraries/boost_1_55_0

  }

}



SOURCES += \

    qtmain.cpp \

    qtwidget.cpp \

    qtitem.cpp



HEADERS += \

    qtwidget.h \

    qtitem.h



RESOURCES += \

    CppQGraphicsPixmapItemExample2.qrc

./CppQGraphicsPixmapItemExample2/qtitem.h


#ifndef QTITEM_H

#define QTITEM_H



#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Weffc++"

#pragma GCC diagnostic ignored "-Wunused-local-typedefs"

#pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

#include <QGraphicsPixmapItem>

#include <boost/signals2.hpp>

#pragma GCC diagnostic pop



///A QGraphicsPixmapItem that loads its pixmap from resources

///and is clickable

struct QtItem : public QGraphicsPixmapItem

{

  QtItem(QGraphicsItem *parent = 0);



  ///Signal emitted when clicked

  boost::signals2::signal<void (QtItem*)> m_clicked_signal;



  protected:

  void mousePressEvent(QGraphicsSceneMouseEvent *event);

};



#endif // QTITEM_H

./CppQGraphicsPixmapItemExample2/qtitem.cpp


#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Weffc++"

#pragma GCC diagnostic ignored "-Wunused-local-typedefs"

#pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

#include <cassert>

#include <QPainter>

#include "qtitem.h"

#pragma GCC diagnostic pop



QtItem::QtItem(QGraphicsItem *parent)

  : QGraphicsPixmapItem(parent),

    m_clicked_signal{}

{

  assert(this->pixmap().isNull()

    && "Assume no pixmap loaded yet");



  //Load the pixmap from resources

  this->setPixmap(QPixmap(":/images/PicR.png"));



  assert(!this->pixmap().isNull()

    && "Assume pixmap is loaded successfully");



  this->setFlags(QGraphicsItem::ItemIsMovable);

}



void QtItem::mousePressEvent(QGraphicsSceneMouseEvent *)

{

  m_clicked_signal(this);

}

./CppQGraphicsPixmapItemExample2/qtmain.cpp


#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Weffc++"

#pragma GCC diagnostic ignored "-Wunused-local-typedefs"

#pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

#include <QApplication>

#include "qtwidget.h"

#pragma GCC diagnostic pop



int main(int argc, char *argv[])

{

  QApplication a(argc, argv);

  QtWidget w;

  w.setGeometry(100,100,400,400);

  w.show();

  return a.exec();

}

./CppQGraphicsPixmapItemExample2/qtwidget.h


#ifndef QTWIDGET_H

#define QTWIDGET_H



#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Weffc++"

#pragma GCC diagnostic ignored "-Wunused-local-typedefs"

#pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

#include <QGraphicsView>

#pragma GCC diagnostic pop



///Forward declaration

struct QtItem;



struct QtWidget : public QGraphicsView

{

  QtWidget();



  ///Respond to a click on a QtItem

  void OnItemClick(QtItem * const item);

};



#endif // QTWIDGET_H

./CppQGraphicsPixmapItemExample2/qtwidget.cpp


#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Weffc++"

#pragma GCC diagnostic ignored "-Wunused-local-typedefs"

#pragma GCC diagnostic ignored "-Wunused-but-set-parameter"

#include <cassert>



#include <boost/bind.hpp>

#include <boost/lambda/bind.hpp>



#include <QGraphicsScene>

#include <QGraphicsPixmapItem>



#include "qtitem.h"

#include "qtwidget.h"

#pragma GCC diagnostic pop



QtWidget::QtWidget()

{

  QGraphicsScene * const scene = new QGraphicsScene(this);

  this->setScene(scene);



  const int n_items = 8;

  for (int i=0; i!=n_items; ++i)

  {

    QtItem * const item = new QtItem;

    item->m_clicked_signal.connect(

      boost::bind(

        &QtWidget::OnItemClick,this, boost::lambda::_1));

    //Scatter those items around a bit

    item->setPos(

      - 128 + (std::rand() % 256),

      - 128 + (std::rand() % 256));



    scene->addItem(item);

  }

}



void QtWidget::OnItemClick(QtItem * const item)

{

  item->setRotation(item->rotation() + 10.0);

}

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(C++) QGraphicsPixmapItemExample2