QGraphicsPixmapItem example 4: pixmap that changes cursor is a QGraphicsPixmapItem example. This example shows how to put multiple movable QGraphicsPixmapItems on screen, let them respond to mouse clicks using a boost::signal, let the user select one or more item (and show this by drawing those items differently) and change the cursor shape when the mouse cursor moves over the item.
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'CppQGraphicsPixmapItemExample4' (zip)
This example is the precedent of QGraphicsObject example 1: basic.
Operating system(s) or programming environment(s)
Lubuntu 15.04 (vivid)
- Qt Creator 3.1.1
- G++ 4.9.2
Libraries used:
Qt project file: ./CppQGraphicsPixmapItemExample4/CppQGraphicsPixmapItemExample4.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 += \ CppQGraphicsPixmapItemExample4.qrc
#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); void hoverMoveEvent(QGraphicsSceneHoverEvent *event); void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget); }; #endif // 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 <cassert> #include <QCursor> #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"); //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 *) { this->setCursor(QCursor(Qt::PointingHandCursor)); } void QtItem::mousePressEvent(QGraphicsSceneMouseEvent *) { //Emit the boost signal m_clicked_signal(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); } }
#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(); }
#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
#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); }