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(C++) QGraphicsSimpleTextItemExample3

 

QtQt CreatorLubuntu

 

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.

 

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: ./CppQGraphicsSimpleTextItemExample3/CppQGraphicsSimpleTextItemExample3.pro

 

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

 

#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

 

#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

 

#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

 

#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

 

#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);
}

 

 

 

 

 

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