I’m sure I’m being dense here, but I’m confused about why my QGraphicsItem
subclass is being called with a different instance when the overrides of the
boundingRect() and paint() functions are being called. Here’s the code…
Header:
|class Entity : public QGraphicsObject { Q_OBJECT public: explicit
Entity(const QString& name, const QSizeF& size); QRectF boundingRect() const
override; void paint(QPainter *painter, const QStyleOptionGraphicsItem
*option, QWidget *widget) override; private: QSizeF entity_size; QString
entity_name; }; |
Module:
|Entity::Entity(const QString& name, const QSizeF& size) : entity_name(name),
entity_size(size) { setAcceptHoverEvents(true); setFlag(ItemIsFocusable,
true); setFlag(ItemIsSelectable, true); setFlag(ItemIsMovable, true); } QRectF
Entity::boundingRect() const { return QRectF(QPointF(0,0), entity_size); }
void Entity::paint(QPainter *painter, const QStyleOptionGraphicsItem*
/*option*/, QWidget* /*widget*/) { ... } |
Main:
|... scene = ScenePointer(new QGraphicsScene(-200, -200, 400, 400)); Entity*
entity = new Entity("Box", QSizeF(100, 100)); entities.push_back(entity);
entity->setPos(-150, -130); scene->addItem(entity); view = ViewPointer(new
QGraphicsView(scene.data())); view->setRenderHint(QPainter::Antialiasing);
view->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
view->setBackgroundBrush(QColor(230, 200, 167));
setCentralWidget(view.data()); ... |
…and here’s the problem…
When I enter the constructor, I have a specific ‘this’ pointer that has the
provided ‘size’ argument placed into its ‘entity_size’ member. However, when
Qt subsequently invokes the boundingRect() override function, it’s an entirely
different ‘this’ instance whose ‘entity_size’ has clearly not been initialized.
I’ve looked at several select examples/widgets/graphicsview/ sources, and
those show that this should be working as expected.
I’ve tested this with 5.11.1 and 5.12.3 with the same result, so I’m guessing
this is some kind of pilot error on my part.
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