The function QGraphicsScene::itemAt problem

[yaseminyilmaz]

Hi all,

I've created a custom class (named as Flow) inherited by QGraphicsItem. It's composing of an arrow and curve. I've used the function itemAt to determine which item has selected when QGraphicsScene::mousePressEvent is called. But it does not always return correct item. Otherwise I've written the folllowing function for manual detection. It's working correctly. But I want to learn why sometimes QGraphicsScene can not detect item selected by pressing mouse? Is there a more sensible method than manual point control?

int getMatchedFlow(QPointF pos)
{
    int fID = -1;
    QList<Flow*> mFlowList = mGroupStore.keys();
    QList<Flow*>::iterator i;
    Flow *pFlow;
 
    for (i = mFlowList.begin(); i != mFlowList.end(); ++i)
    {
        pFlow = (Flow*)*i;
        if (pFlow->checkPointSet(pos))
        {
            fID = pFlow->getID();
            break;
        }
    }
 
    return fID;
}
 
bool Flow::checkPointSet(QPointF point)
{
    bool rc = false;
 
    if (mBoundingPath.contains(point))
    {
        rc = true;
    }
 
    return rc;
}

int getMatchedFlow(QPointF pos)
{
    int fID = -1;
    QList<Flow*> mFlowList = mGroupStore.keys();
    QList<Flow*>::iterator i;
    Flow *pFlow;

    for (i = mFlowList.begin(); i != mFlowList.end(); ++i)
    {
        pFlow = (Flow*)*i;
        if (pFlow->checkPointSet(pos))
        {
            fID = pFlow->getID();
            break;
        }
    }

    return fID;
}

bool Flow::checkPointSet(QPointF point)
{
    bool rc = false;

    if (mBoundingPath.contains(point))
    {
        rc = true;
    }

    return rc;
}

To copy to clipboard, switch view to plain text mode 

Thanks a lot for your helps,

[wysota]

How did you implement boundingRect() and shape() for your item?

[yaseminyilmaz]

I've implemented as following. I've noticed that sometimes getMatchedFlow has not detect when I click the arrow in addition to the function QGraphicsScene::itemAt. What can the problem be?

QPainterPath Flow::shape() const
{
    return mBoundingPath;
}
 
QRectF Flow::boundingRect() const
{
    return mRectF;
}
 
void Flow::updateBoundingRect()
{
    prepareGeometryChange();
 
    mBoundingPath = QPainterPath();
 
    addArrow();  // it adds arrow polygon to mBoundingPath
    addCurve();  // it adds curve path to mBoundingPath
 
    mRectF = mBoundingPath.boundingRect();
 
    updateScene();
}

QPainterPath Flow::shape() const
{
    return mBoundingPath;
}

QRectF Flow::boundingRect() const
{
    return mRectF;
}

void Flow::updateBoundingRect()
{
    prepareGeometryChange();

    mBoundingPath = QPainterPath();

    addArrow();  // it adds arrow polygon to mBoundingPath
    addCurve();  // it adds curve path to mBoundingPath

    mRectF = mBoundingPath.boundingRect();

    updateScene();
}

To copy to clipboard, switch view to plain text mode 

[wysota]

Do you have overlapping items? If so, do you have different zorder set for them?