QGraphicsPixmapItem example example 7: respond to cursor moving over pixmap while holding the cursor still is a QGraphicsPixmapItem example. This example shows how to let the QGraphicsView responds to the cursor being moved over the QGraphicsPixmapItem, where the pixmap keeps responding even when the mouse cursor is held still.
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'CppQGraphicsPixmapItemExample7' (zip)
QGraphicsPixmapItem example 6: let the view respond to cursor moving over pixmap is the predecessor of QGraphicsPixmapItem example 7: respond to cursor moving over pixmap while holding the cursor still.
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: ./CppQGraphicsPixmapItemExample7/CppQGraphicsPixmapItemExample7.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 \ qthighlighter.cpp HEADERS += \ qtwidget.h \ qtitem.h \ qthighlighter.h RESOURCES += \ CppQGraphicsPixmapItemExample7.qrc
#ifndef QTHIGHLIGHTER_H #define QTHIGHLIGHTER_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 <QObject> #pragma GCC diagnostic pop struct QGraphicsItem; struct QTimer; class QtHighlighter : public QObject { Q_OBJECT public: QtHighlighter(QObject *parent = 0); ///Set the item to highlight. ///If set with a nullptr, highlighting the current item stops ///If set with the same item twice, nothing new happens void SetItem(QGraphicsItem * const item); private: ///The item being highlighted QGraphicsItem * m_item; ///The timer used for highlighting every 100 ms QTimer * const m_timer; private slots: void OnTimer(); }; #endif // QTHIGHLIGHTER_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 <QGraphicsItem> #include <QTimer> #include "qthighlighter.h" #pragma GCC diagnostic pop QtHighlighter::QtHighlighter(QObject *parent) : QObject(parent), m_item(nullptr), m_timer(new QTimer(this)) { m_timer->setInterval(10); //ms QObject::connect( m_timer,SIGNAL(timeout()), this,SLOT(OnTimer())); } void QtHighlighter::SetItem(QGraphicsItem * const item) { m_item = item; if (m_item) { this->m_timer->start(); } else { this->m_timer->stop(); } } void QtHighlighter::OnTimer() { if (m_item) { m_item->setRotation(m_item->rotation() + 5.0); } }
#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> #pragma GCC diagnostic pop ///A QGraphicsPixmapItem that loads its pixmap from resources ///and is clickable struct QtItem : public QGraphicsPixmapItem { QtItem(QGraphicsItem *parent = 0); protected: 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) { 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); } 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 QtHighlighter; struct QtWidget : public QGraphicsView { QtWidget(); protected: void mouseMoveEvent(QMouseEvent *event); private: ///Class highlighting a QGraphicsItem QtHighlighter * const m_highlighter; }; #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 <iostream> #include <boost/bind.hpp> #include <boost/lambda/bind.hpp> #include <QGraphicsScene> #include <QGraphicsPixmapItem> #include <QMouseEvent> #include "qthighlighter.h" #include "qtitem.h" #include "qtwidget.h" #pragma GCC diagnostic pop QtWidget::QtWidget() : m_highlighter(new QtHighlighter(this)) { 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; //Scatter those items around a bit item->setPos( - 128 + (std::rand() % 256), - 128 + (std::rand() % 256)); scene->addItem(item); } ///Without this line, mouseMoveEvent will not be called this->setMouseTracking(true); } void QtWidget::mouseMoveEvent(QMouseEvent *event) { //Rotate the first item found under the cursor { //Find the items under the cursor QList<QGraphicsItem *> all_items = this->scene()->items(); std::vector<QGraphicsItem *> items; //The items under the cursor const QPointF pos = this->mapToScene(event->pos()); std::for_each(all_items.begin(),all_items.end(), [this,&items,pos](QGraphicsItem * item) { const QRectF rect = item->boundingRect().translated(item->pos()); if (rect.contains(pos)) { items.push_back(item); } } ); //Rotate the possible first item found if (!items.empty()) { m_highlighter->SetItem(items[0]); } else { m_highlighter->SetItem(nullptr); } } //Let QGraphicsView handle the default mouseMoveEvents, for example //the moving of the items QGraphicsView::mouseMoveEvent(event); }