Go back to Richel Bilderbeek's homepage.

Go back to Richel Bilderbeek's C++ page.

 

 

 

 

 

(C++) QGraphicsPixmapItemExample5

 

QGraphicsPixmapItem example 5: respond to cursor moving over pixmap is a QGraphicsPixmapItem example. This example shows how to let the QGraphicsPixmapItem emit a (Boost) signal so that the QGraphicsView can rotate it. It is usefull to be able to send signals to the QGraphicsView, because QGraphicsView is a QObject, where QGraphicsPixmapItem is not. Due to this, the item cannot work with Qt signals, but the view can (note that QGraphicsObject is a QGraphicsItem that can work with signals and slots).

 

 

QGraphicsPixmapItem example 5: respond to cursor moving over pixmap is the predecessor of QGraphicsPixmapItem example 6: let the view respond to cursor moving over pixmap, which is the predecessor of QGraphicsPixmapItem example 7: respond to cursor moving over pixmap while holding the cursor still.

Technical facts

 

Application type(s)

Operating system(s) or programming environment(s)

IDE(s):

Project type:

C++ standard:

Compiler(s):

Libraries used:

 

 

 

 

 

Qt project file: ./CppQGraphicsPixmapItemExample5/CppQGraphicsPixmapItemExample5.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 += \
    CppQGraphicsPixmapItemExample5.qrc

 

 

 

 

 

./CppQGraphicsPixmapItemExample5/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 the cursor moves over this item
  boost::signals2::signal<void (QtItem*)> m_signal_move_over;


  protected:
  void hoverMoveEvent(QGraphicsSceneHoverEvent *event);

  void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

};

#endif // QTITEM_H

 

 

 

 

 

./CppQGraphicsPixmapItemExample5/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 <QCursor>
#include <QPainter>
#include "qtitem.h"
#pragma GCC diagnostic pop

QtItem::QtItem(QGraphicsItem *parent)
  : QGraphicsPixmapItem(parent),
    m_signal_move_over{}
{
  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");

  //Let the item have (0.0,0.0) as its center,
  //so it will remain in place when rotating
  this->setOffset(-pixmap().rect().center());

  this->setFlags(
      QGraphicsItem::ItemIsMovable
    | QGraphicsItem::ItemIsSelectable
  );

  //Without this line, hoverMoveEvent will not be called
  this->setAcceptHoverEvents(true);
}

void QtItem::hoverMoveEvent(QGraphicsSceneHoverEvent *)
{
  //Emit the boost signal
  m_signal_move_over(this);
}

void QtItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
  //Let QGraphicsPixmapItem handle most of the painting
  QGraphicsPixmapItem::paint(painter,option,widget);

  //Draw a thick red line around the pixmap when it is selected
  if (this->isSelected())
  {
    painter->setPen(QPen(QColor(255,0,0),3));
    painter->drawRoundedRect(this->boundingRect().adjusted(3.0,3.0,-3.0,-3.0),6.0,6.0);
  }
}

 

 

 

 

 

./CppQGraphicsPixmapItemExample5/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();
}

 

 

 

 

 

./CppQGraphicsPixmapItemExample5/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 OnItemMoveOver(QtItem * const item);
};

#endif // QTWIDGET_H

 

 

 

 

 

./CppQGraphicsPixmapItemExample5/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_signal_move_over.connect(
      boost::bind(
        &QtWidget::OnItemMoveOver,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::OnItemMoveOver(QtItem * const item)
{
  item->setRotation(item->rotation() + 10.0);
}

 

 

 

 

 

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.

 

Valid XHTML 1.0 Strict

This page has been created by the tool CodeToHtml