QML Dynamically created object lifetime

Question

I'm testing a custom popup menu strategy when I came across some odd behaviour: Requests to delete my dynamically created popup window are ignored.

Window {
    id: window
    width: 400
    height: 400
    color: "red"

    Rectangle {
        id: base
        width: 100
        height: 100
        anchors.centerIn: parent
        color: "green"

        property Window parentWindow: window
        property Window popup: null

        MouseArea {
            anchors.fill: parent
            onClicked: {
                base.popup = popupComp.createObject( null, { "parentWindow": base.parentWindow } );
            }
        }

        Connections {
            target: base.parentWindow
            onClosing: {
                if ( base.popup !== null ) {
                    base.popup.hide();
                    base.popup.destroy(); // 2
                }
            }
        }

        Component {
            id: popupComp

            Window {
                width: 150
                height: 150
                x: parentWindow.x + base.mapToItem( null, 0, 0 ).x
                y: parentWindow.y + base.mapToItem( null, 0, base.height ).y

                flags: Qt.Popup
                color: "blue"
                visible: true

                property Window parentWindow: null

                Component.onCompleted: requestActivate()

                Component.onDestruction: {
                    console.log( "Destroying popup" );
                }

                onActiveChanged: {
                    if ( !active ) {
                        console.log( "Popup inactive" );
                        hide();
                        base.popup = null;
                        destroy(); // 1
                    }
                }
            }
        }
    }
}

I have to create the popup window dynamically because it's the only way to specify no parent, as a subwindow's (i.e. a parented window) QWindow::active state seems to be dependent upon it's parent's.

Once the popup window is closed the popup's destroy() slot is called via the onActiveChanged handler - but object is not destroyed until the parent window's closing() signal is emitted. Here is the debug output from opening and closing the popup twice:

qml: Popup inactive
qml: Popup inactive
// Closing the parent window now
qml: Destroying popup
qml: Destroying popup

Any idea why the destroy() call at 1 is ignored whilst granted at 2?

Mitch Mitch · Accepted Answer · 2014-10-27T16:59:28

I'd say it has something to do with it not being ready to process the call yet.

Along the lines of that guess, enforcing a delay before the destruction occurs seems to be a decent workaround:

thisWindow.destroy(1);

QML Dynamically created object lifetime

1 Answers