[Solved]Problem selecting a QGraphicsItem child.

MaQzma

Hi,

To select a QGraphicsItem child I call child->setSelected(true) in itemChange function every time the selected state changes. But when I release the mouse at the same mouse press point/position, the child item is deselected.

The strange thing is that the child item is no deselected if I move the mouse before I release the mouse:

Press the mouse into the parent item.

Move the mouse (pressing).

Release the mouse (diferent from press point/position).

Child is no deselected, it's selected.

Why is this happening?

Here is the code if you want to try it... :)
@
#include <QtGui>
#include <QtCore>

class Item : public QGraphicsRectItem
{
public:
Item(const QRectF &rect, QGraphicsItem *parent = 0) :
QGraphicsRectItem(rect, parent) {

    // Create the item
    _otherItem = new QGraphicsRectItem(20, 20, 10, 10, this);

    // Configure the item ~ Is selectable
    _otherItem->setPen(QPen(Qt::black));
    _otherItem->setBrush(QBrush(Qt::green));
    _otherItem->setFlag(QGraphicsItem::ItemIsSelectable, true);
}

protected:
QVariant itemChange(GraphicsItemChange change, const QVariant &value) {

    // If the item's selected state changes
    if (change == QGraphicsItem::ItemSelectedChange) {

        // If is selected
        if (value.toBool() == true) {

            // Show _otherItem and select it
            _otherItem->setSelected(true);
        }
        else {
            _otherItem->setSelected(false);
        }
    }

    return QGraphicsRectItem::itemChange(change, value);
}

private:
QGraphicsRectItem *_otherItem;
};

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

QGraphicsScene scene;

// Create and configure the item ~ Is selectable
Item *rect = new Item(QRectF(0, 0, 50, 50));
rect->setPen(QPen(Qt::black));
rect->setBrush(QBrush(Qt::red));
rect->setFlag(QGraphicsItem::ItemIsSelectable, true);
scene.addItem(rect);

QGraphicsView view(&scene);
view.show();

return app.exec&#40;&#41;;

}
@

Thanks.

MaQzma

Hi,

The answer is in qgraphicsitem.cpp file at mouseReleaseEvent function, the comment says:

@
if (event->scenePos() == event->buttonDownScenePos(Qt::LeftButton)) {
// The item didn't move
if (multiSelect) {
setSelected(!isSelected());
} else {
...
// Clear everything but this item. Bypass
// QGraphicsScene::clearSelection()'s default behavior by
// temporarily removing this item from the selection list.
...
scene->clearSelection();
...
}
}
@

Mario.