[Qt-interest] QGraphicsScene pos

[Sean Harmer]

Hi,

> myScene->setSceneRect( -50.0, -50.0, 50.0, 50.0 );
> on the following event handler, I want the x and y within the scene rect.

> void MyGraphicsScene::mouseDoubleClickEvent ( QGraphicsSceneMouseEvent *
> mouseEvent)
> {
>     QRectF rect = sceneRect();  //this gives -50.0, -50.0, 50.0, 50.0
> 
>     //but the following returns something out of the sceneRect - e.g. 106,
> -91 double-clicking in the top right corner
> 
>     QPointF pointScene = mouseEvent->lastScenePos ();
> 
>     // is it a view related point?
>    QPointF point = this->views()[0]->mapToScene(pointScene.toPoint()); //
> but this returns -51, -183
> }
> 
> The QGraphicsView is added into a layout and the mainWindow is resizable,
> so the size of the widget is not fixed.

By default the scene is displayed in the view at a scale of 1.0. So if your 
view's viewport is larger than 100x100 pixels then it will be displaying 
regions outside of your scenerect so the above code and results looks feasible 
to me.

If you want your scene to fill your view you will need to call 
QGraphicsScene::fitInView() to change the view transformation before you start 
double-clicking.

This type of thing is much easier to visualise if you add a small rect at each 
corner of your scene rect for example.

HTH,

Sean

> 
> 
> 
> thanks
> 
> pm