(C++) QGraphicsProxyWidget example 6

QGraphicsProxyWidget example 6 is a QGraphicsProxyWidget example.

This example shows to be able to move the MyItem, even when MyItem has a focusable QLineEdit.

Technical facts

Application type(s)

Desktop application

Operating system(s) or programming environment(s)

Lubuntu 12.10 (quantal)

IDE(s):

Qt Creator 2.5.2

Project type:

GUI application

C++ standard:

C++11

Compiler(s):

G++ 4.7.2

Libraries used:

Qt: version 4.8.3 (32 bit)
STL: GNU ISO C++ Library, version 4.7.2

Qt project file: CppQGraphicsProxyWidgetExample6.pro


QT       += core

QT       += gui

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

TARGET = CppQGraphicsProxyWidgetExample6

CONFIG   += console

CONFIG   -= app_bundle

TEMPLATE = app

SOURCES += main.cpp \

    myitem.cpp \

    myview.cpp



HEADERS += \

    myitem.h \

    myview.h

main.cpp


#ifdef _WIN32

//See http://www.richelbilderbeek.nl/CppCompileErrorSwprintfHasNotBeenDeclared.htm

#undef __STRICT_ANSI__

#endif



#pragma GCC diagnostic ignored "-Weffc++"

#include <QApplication>

#include <QDesktopWidget>

#pragma GCC diagnostic pop



#include "myview.h"



int main(int argc, char **argv)

{

  //Create the application

  QApplication app(argc, argv);

  MyView view;

  view.setGeometry(0,0,800,600);

  {

    //Put the dialog in the screen center

    const QRect screen = QApplication::desktop()->screenGeometry();

    view.move( screen.center() - view.rect().center() );

  }

  view.show();

  return app.exec();

}

myitem.h


#ifndef MYITEM_H

#define MYITEM_H



#include <QWidget>

#include <boost/signals2.hpp>



struct QLabel;

struct QLineEdit;



class MyItem : public QWidget

{

  Q_OBJECT



  public:

  explicit MyItem(QWidget *parent = 0, Qt::WindowFlags f = 0);

  boost::signals2::signal<void (MyItem*)> m_signal_mouse_press;

  boost::signals2::signal<void (MyItem*)> m_signal_lose_focus;

  protected:

  void mousePressEvent(QMouseEvent * event);

  void mouseDoubleClickEvent(QMouseEvent * event);

  public slots:

  void LoseFocus();



  public:

  QLineEdit * const m_edit;

  QLabel * const m_label;

};



#endif // MYITEM_H

myitem.cpp


#ifdef _WIN32

//See http://www.richelbilderbeek.nl/CppCompileErrorSwprintfHasNotBeenDeclared.htm

#undef __STRICT_ANSI__

#endif



//#include own header file as first substantive line of code, from:

// * John Lakos. Large-Scale C++ Software Design. 1996. ISBN: 0-201-63362-0. Section 3.2, page 110

#include "myitem.h"



#pragma GCC diagnostic ignored "-Weffc++"

#include <QLineEdit>

#include <QLabel>

#include <QVBoxLayout>

#pragma GCC diagnostic pop



#include "myitem.h"



MyItem::MyItem(QWidget *parent, Qt::WindowFlags f)

  : QWidget(parent,f),

    m_edit(new QLineEdit(this)),

    m_label(new QLabel(this))

{

  assert(!this->layout());

  QVBoxLayout * const layout = new QVBoxLayout(this);

  this->setLayout(layout);

  layout->addWidget(m_label);

  layout->addWidget(m_edit);

  QObject::connect(m_edit,SIGNAL(returnPressed()),this,SLOT(LoseFocus()));

}



void MyItem::LoseFocus()

{

  //Really get rid of the focus

  this->clearFocus();

  this->setEnabled(false);

  m_signal_lose_focus(this);

  //Enable the item again

  this->setEnabled(true);

}



void MyItem::mousePressEvent(QMouseEvent * event)

{

  m_signal_mouse_press(this);

  QWidget::mousePressEvent(event);

}





void MyItem::mouseDoubleClickEvent(QMouseEvent *)

{

  LoseFocus();

}

myview.h


#ifndef MYVIEW_H

#define MYVIEW_H



#include <QGraphicsView>





#include "myitem.h"



struct MyItem;

struct QGraphicsScene;



class MyView : public QGraphicsView

{

  Q_OBJECT



  public:

  explicit MyView(QWidget *parent = 0);



  protected:

  void mouseMoveEvent(QMouseEvent *event);

  void mouseReleaseEvent(QMouseEvent *);



  private:

  QGraphicsScene * const m_scene;

  MyItem * m_drag_item;

  std::map<MyItem *,QGraphicsProxyWidget *> m_m;



  //My own added method

  void OnMousePress(MyItem * item);

  //An item wants to get rid of its focus

  void OnItemNoFocus(MyItem * item);

};



#endif // MYVIEW_H

myview.cpp


#ifdef _WIN32

//See http://www.richelbilderbeek.nl/CppCompileErrorSwprintfHasNotBeenDeclared.htm

#undef __STRICT_ANSI__

#endif



//#include own header file as first substantive line of code, from:

// * John Lakos. Large-Scale C++ Software Design. 1996. ISBN: 0-201-63362-0. Section 3.2, page 110

#include "myview.h"





#include <cassert>

#include <cmath>



#pragma GCC diagnostic ignored "-Weffc++"

#include <QGraphicsProxyWidget>

#include <QGraphicsScene>

#include <QLabel>

#include <QLineEdit>

#include <QDialog>

#include <QGraphicsSceneMouseEvent>

#pragma GCC diagnostic pop





MyView::MyView(QWidget *parent)

  : QGraphicsView(parent),

    m_scene(new QGraphicsScene(this)),

    m_drag_item(nullptr)

{

  this->setScene(m_scene);

  //Create the QLineEdit instances

  const int sz = 10;

  std::vector<QGraphicsProxyWidget *> proxies;

  for (int i=0; i!=sz; ++i)

  {

    MyItem * const item = new MyItem;

    item->setGeometry(0,0,100,22);

    item->m_label->setText(QString("#") + QString::number(i));

    item->m_edit->setText(QString("Text ") + QString::number(i));

    item->m_signal_mouse_press.connect(

      boost::bind(

        &MyView::OnMousePress,

        this,_1)); //_1 because the signal contains an argument

    item->m_signal_lose_focus.connect(

      boost::bind(

        &MyView::OnItemNoFocus,

        this,_1)); //_1 because the signal contains an argument

    //Add the QWidget and obtain its proxy

    QGraphicsProxyWidget * const proxy = m_scene->addWidget(item);

    proxies.push_back(proxy);

    m_m[item] = proxy;

  }



  const double ray = 200.0; //pixels

  for (int i=0; i!=sz; ++i)

  {

    const double angle = 2.0 * M_PI * static_cast<double>(i) / static_cast<double>(sz);

    const int x = static_cast<int>(0.0 + (std::sin(angle) * ray));

    const int y = static_cast<int>(0.0 - (std::cos(angle) * ray));

    QGraphicsProxyWidget * const proxy = proxies[i];

    proxy->setRotation(angle * 360.0 / (2.0 * M_PI));

    proxy->setPos(x,y);

    proxy->setFlag(QGraphicsItem::ItemIsMovable,true); //No need to set this flag

  }

}



void MyView::OnMousePress(MyItem * item)

{

  assert(item);

  m_drag_item = item;

  //item->m_edit->setText("Gotcha!");

}



void MyView::OnItemNoFocus(MyItem * item)

{

  assert(item);

  //item->m_edit->setText("Lost focus");

  this->setFocus();

  m_drag_item = nullptr;

  assert(!m_drag_item);

}



void MyView::mouseMoveEvent(QMouseEvent *event)

{

  if (m_drag_item)

  {

    //Convert the position clicked to the QGraphicsView coordinat

    const QPointF p = this->mapToScene(event->pos());

    //Let the item follow the mouse cursor

    m_m[m_drag_item]->setPos(p);

  }

}



void MyView::mouseReleaseEvent(QMouseEvent *)

{

  m_drag_item = nullptr;

}

crosscompiletowindows.sh


#!/bin/sh

#From http://richelbilderbeek.nl/CppQtCrosscompileToWindowsExample15.htm



echo "Cross compiling to Windows"



echo "1/2: Creating Windows makefile"

i686-pc-mingw32-qmake CppQGraphicsProxyWidgetExample6.pro



echo "2/2: making makefile"



make



echo "Done"

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