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(C++) QGraphicsRectItemExample4

 

QtQt CreatorLubuntu

 

QGraphicsRectItem example 4: varying pen widths is a QGraphicsRectItem example that displays multiple QGraphicsRectItems. These items are movable and selectable. Additionally, the items display their width, height and pen width, on a linear gradient.

 

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Qt project file: ./CppQGraphicsRectItemExample4/CppQGraphicsRectItemExample4.pro

 

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

SOURCES += \
    qtmain.cpp \
    qtwidget.cpp \
    qtrectitem.cpp

HEADERS += \
    qtwidget.h \
    qtrectitem.h

 

 

 

 

 

./CppQGraphicsRectItemExample4/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 <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();
}

 

 

 

 

 

./CppQGraphicsRectItemExample4/qtrectitem.h

 

#ifndef QTRECTITEM_H
#define QTRECTITEM_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 <QGraphicsRectItem>
#pragma GCC diagnostic pop

struct QtRectItem : public QGraphicsRectItem
{
  QtRectItem(QGraphicsItem *parent = 0);

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

#endif // QTRECTITEM_H

 

 

 

 

 

./CppQGraphicsRectItemExample4/qtrectitem.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 "qtrectitem.h"

#include <cassert>
#include <sstream>
#include <QGraphicsScene>
#include <QLinearGradient>
#include <QPainter>
#pragma GCC diagnostic pop

QtRectItem::QtRectItem(QGraphicsItem *parent)
: QGraphicsRectItem(parent)
{
  this->setFlags(
      QGraphicsItem::ItemIsFocusable
    | QGraphicsItem::ItemIsMovable
    | QGraphicsItem::ItemIsSelectable
  );
}

void QtRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{

  //Resize the rect to the text its size (using QFontMetrics to find this out)
  QFontMetrics q(painter->font());
  const double width = q.width("(9999x9999x123456.7890)");
  const double height = q.height();
  const QRectF text_rect(-0.5 * width, -0.5 * height, width, height);
  const double padding = 4.0;
  this->setRect(text_rect.adjusted(-padding,-padding,padding,padding));

  {
    QLinearGradient g(this->rect().topLeft(),this->rect().bottomRight());
    g.setColorAt(0.0,QColor(128,128,128));
    g.setColorAt(1.0,QColor(240,240,240));
    this->setBrush(g);
  }

  //Let QGraphicsRectItem handle the default painting
  QGraphicsRectItem::paint(painter,option,widget);

  //Create the initial
  std::stringstream s;
  s << "(" << rect().width()
    << " x " << rect().height() << "), "
    << this->pen().widthF()
  ;
  const std::string t = s.str();

  //Draw the text on the drawn rectangle
  painter->drawText(text_rect,t.c_str());
}

 

 

 

 

 

./CppQGraphicsRectItemExample4/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

///The widget holding the items
struct QtWidget : public QGraphicsView
{
  QtWidget(QWidget *parent = 0);
};

#endif // QTWIDGET_H

 

 

 

 

 

./CppQGraphicsRectItemExample4/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 "qtwidget.h"
#include <QGraphicsScene>
#include "qtrectitem.h"
#pragma GCC diagnostic pop

QtWidget::QtWidget(QWidget *parent)
  : QGraphicsView(new QGraphicsScene,parent)
{
  const int n_items = 20;
  for (int i=0; i!=n_items; ++i)
  {
    const double x = static_cast<double>(i % 2) * 200.0;
    const double y = static_cast<double>(i / 2) * 40;
    QPen pen;
    pen.setWidth(i);
    QtRectItem * const item = new QtRectItem;
    item->setPos(x,y);
    item->setPen(pen);
    scene()->addItem(item);
  }
}

 

 

 

 

 

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