CODEWITHSUNDEEP
c++qtgraphicsqgraphicssceneqgraphicsitem
CharlieKeith
CharlieKeith

Reputation: 55

QGraphicsItems not showing up QGraphicsScene

I'm trying to build a custom widget with a QGraphicsScene inside it.

class Graphics:public QWidget{
  public:
 Graphis();
}

Graphics::Graphics(){
 QGraphicsScene* scene = new QGraphicsScene(this);
    
    
    QGridLayout* grid = new QGridLayout;

    
    
    QGraphicsView* view = new QGraphicsView(this);
    
    
    QGraphicsLineItem* y = new QGraphicsLineItem(scene->width()/2, 0, scene->width() / 2, scene->height());
    QGraphicsLineItem* x = new QGraphicsLineItem(0, scene->height() / 2, scene->width(), scene->height() / 2);
    scene->addItem(y);
    scene->addItem(x);
    
    

    grid->addWidget(view, 0, 0, 1, 1);
    setLayout(grid);

    view->setScene(scene);
    view->show();
}

But when I run the widget, only an empty scene shows up in the QGraphicsView widget inside the main widget.

Upvotes: 0

Views: 671

Answers (1)

Jeremy Friesner
Jeremy Friesner

Reputation: 73304

Try it like this instead; I think one problem is that scene->width() and scene->height() are very likely both returning 0, at least on your first call to them, since sceneRect() defaults to returning a QRect big enough to fit the current contents of the scene (which is initially empty):

Graphics::Graphics(){
    QGraphicsScene* scene = new QGraphicsScene(this);
    QGridLayout* grid = new QGridLayout(this);
    QGraphicsView* view = new QGraphicsView(scene, this);

    scene->setSceneRect(0, 0, 200, 200);
    QGraphicsLineItem* y = new QGraphicsLineItem(scene->width()/2, 0, scene->width() / 2, scene->height());
    QGraphicsLineItem* x = new QGraphicsLineItem(0, scene->height() / 2, scene->width(), scene->height() / 2);
    scene->addItem(y);
    scene->addItem(x);

    grid->addWidget(view, 0, 0, 1, 1);
}

Upvotes: 1

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