Question

I’ve created an object Chartblock that implements QGraphicsItem. My goal is to create a grid of these objects, and when the mouse button is pressed (and held) and is drug over each block, perform something on each block as the cursor enters it.

Since a QGraphicsItem grabs the mouse events when it is clicked within it, other Items will not fire for the mouseMoveEvent. I then created an object based on the QGraphicsItemGroup to handle all the mouse events, but then I would need some way to pass mousePressEvent/mouseReleaseEvent as well as mouseMoveEvent to each child that the cursor is over.

Am I overthinking how to do this? It seems like such a simple action shouldn’t be that difficult to create, but with QGraphicsItems holding onto the mouse events for itself, I’m not sure how to get around it. I’ve read similar situations, but nothing seems to give a straightforward answer.

Edit: I suppose a way to do this would keep track of the coordinates/sizes of every single QGraphicsItem I create in an array, then get the position of the cursor in the Group mouseMoveEvent, and see if there’s a hit..

Answer 1

I was able to pull together a few similar answers to create a solution; I dropped the idea of placing all my QGraphicItem’s in a Group, and placed them directly on a scene. With the scene grabbing all mouse events, I have the mouseMoveEvent check to see if the current position is on top of a QGraphicsItem – if so, perform something.

I still need to try and get itemAt() to work for my own classes that implement QGraphicsItem, as itemAt returns only QGraphicsItem’s, but I’m sure some cast should get it working.

void ChartScene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
    QPointF mousePosition = event->scenePos();
    QGraphicsItem* pItem = this->itemAt(mousePosition.x(), mousePosition.y());
}