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c++qtqgraphicsviewqgraphicsitem

How to draw a triangle by using QGraphicsView's QGraphicsItem class

I want to draw a triangular object in QGraphicsView by using QGraphicsItem. But I don't know how to implement bounding rect according to triangler.

Solution

  • You could use a QGraphicsPolygonItem.

    You just have to describe a triangle polygon with QPolygonF and then add it to your scene with QGraphicsScene::addPolygon().

    // Describe a closed triangle
QPolygonF Triangle;
Triangle.append(QPointF(-10.,0));
Triangle.append(QPointF(0.,-10));
Triangle.append(QPointF(10.,0));
Triangle.append(QPointF(-10.,0));

// Add the triangle polygon to the scene
QGraphicsPolygonItem* pTriangleItem = pScene->addPolygon(Triangle);

    This way, everything is handled by Qt, you don't have to worry about bounding rect.