[SailfishDevel] QQmlComponent: Cannot create new component instance before completing the previous

[Krisztian Olah]

Hi all, I've just introduced a bug that could cause segfault. It is unknown
to me what conditions trigger the bug exactly. I'm clueless as to why it
happens, I would be greatful for any kind of help.

I attached the error in a txt file I got in console when it crashed.
Basically a lot of: "QQmlComponent: Cannot create new component instance
before completing the previous"
and underneath "speed: $SOMEDOUBLE" was the result of:


Component.onCompleted: {

                console.log("**** speed: " +
(messageLabel.paintedWidth - self.width) )

}

in messageLabel. So for some reason it wanted to construct a whole bunch of
Labels until it ran out of stack memory.

When the code works as expected I still get this warning/error msg just not
as many and don't crash:
"QQmlComponent: Cannot create new component instance before completing the
previous"

Here is the code in question:
RunningText is in StopHeader which is in turn a headerItem of a
SilicaListView the bug occurs(given unknown conditions which are rare) when
pushing the Page containig this SilicaListView
for a greater context see: https://github.com/KrisztianOlah/london-sail/


//RunnungText.qml

Item {

    id: self

    property color backgroundColor: Theme.highlightColor

    property double backgroundOpacity: 0.4

    property color textColor: Theme.highlightDimmerColor


    state: (messageLabel.text === "") ? "invisible" : "visible"

    Connections {

        target: arrivalsData

        onCurrentStopMessagesChanged: {

            messageLabel.text = arrivalsData.getCurrentStopMessages()

        }

    }


    Rectangle {

        id: shade

        color: backgroundColor

        opacity: backgroundOpacity

        anchors.fill: parent

        Label {

            id: messageLabel

            color: textColor

            clip: true

            text: arrivalsData.getCurrentStopMessages()

            anchors.verticalCenter: parent.verticalCenter

            onTextChanged: {

                state = (messageLabel.text === "") ? "invisible" : "visible"

                arrivalsData.refreshArrivalsModel()

            }

        }

        NumberAnimation {

            id: animation

            target: messageLabel

            from: parent.width

            to: 0 - messageLabel.paintedWidth

            //should have the same speed for any length text

            duration: (messageLabel.paintedWidth + self.width) * 5

            property: "x"

            running: true

            loops: Animation.Infinite

        }


    }

    OpacityRampEffect {

        sourceItem: shade

        direction: OpacityRamp.RightToLeft

        slope: 0.5

        offset: 0.001

    }

    states: [

        State {

            name: "visible"

            PropertyChanges {

                target: self

                height: 50

            }

        },

        State {

            name: "invisible"

            PropertyChanges {

                target: self

                height: 0

            }

        }


    ]

}


//StopHeader.qml

Item {

    id: self

    property Stop currentStop: arrivalsData.getCurrentStop()

    property string stopPointIndicator: currentStop.getStopPointIndicator()

    property string direction: currentStop.getTowards()

    property alias distance: distanceLabel.text

    property string message: ""

    property string stopCode: currentStop.getID()

    property int type: currentStop.getType()

    property string title: currentStop.getName()

    property bool isFavorite: arrivalsData.isStopFavorite(stopCode)

    property double headerOpacity: Theme.highlightBackgroundOpacity


    Connections {

        target: self.currentStop

        onDataChanged: {

            self.stopPointIndicator = currentStop.getStopPointIndicator()

            self.direction = currentStop.getTowards()

            self.distance = distanceLabel.text

            self.stopCode = currentStop.getID()

            self.type = currentStop.getType()

            self.title = currentStop.getName()

            self.isFavorite = arrivalsData.isStopFavorite(stopCode)


        }

    }


    anchors {

        left: parent.left

        right: parent.right

    }

    height: pageHeader.height + stopHeader.height + messageBox.height
+ Theme.paddingMedium*4


    Label {

        id: pageHeader

        text: title

        font.pixelSize: Theme.fontSizeLarge

        color: Theme.highlightColor

        horizontalAlignment: Text.AlignRight

        wrapMode: Text.WordWrap

        anchors {

            top: parent.top

            topMargin: Theme.paddingMedium*2

            right: parent.right

            rightMargin: Theme.paddingLarge

            left: parent.left

            leftMargin: 130

        }

    }

    RunningText {

        id: messageBox

        anchors {

            top: pageHeader.bottom

            topMargin: Theme.paddingMedium*2

            left: parent.left

            right: parent.right

        }

    }


    Rectangle {

        id: stopHeader

        height: directionLabel.paintedHeight + Theme.paddingMedium*2

        color: Theme.highlightBackgroundColor

        opacity: headerOpacity

        anchors {

            top: messageBox.bottom

            left: parent.left

            right: parent.right

        }

    }

    StopIcon {

        id: icon

        stopPointIndicator: self.stopPointIndicator

        type: self.type

        anchors {

            verticalCenter: stopHeader.verticalCenter

            left: stopHeader.left

            leftMargin: Theme.paddingSmall

        }

    }

    IconButton {

        id: favoriteButton

        icon.source: isFavorite ? "image://theme/icon-l-favorite" :
"image://theme/icon-l-star"

        anchors {

            right: stopHeader.right

            verticalCenter: stopHeader.verticalCenter

        }

        onClicked: {

            if (!isFavorite) {

                self.currentStop.addToDb(true)//won't do anything if
record is already in db

                arrivalsData.favorStop(stopCode, true)//make sure it
is favorite in case record was already in db

                isFavorite = arrivalsData.isStopFavorite(stopCode)

            }

            else {

                arrivalsData.favorStop(stopCode, false)

                isFavorite = arrivalsData.isStopFavorite(stopCode)

            }

        }

    }

    Label {

        id: towardsLabel

        text: (directionLabel.text !== "" && (type === Stop.Bus ||
type === Stop.River)) ? "towards" : ""

        font.pixelSize: Theme.fontSizeTiny

        color: Theme.highlightColor

        anchors {

            left: icon.right

            leftMargin: Theme.paddingExtraLarge

            top: stopHeader.top

            topMargin: Theme.paddingSmall

        }

    }


    Label {

        id: directionLabel

        text: currentStop.getTowards()

        color: Theme.highlightColor

        wrapMode: Text.WordWrap

        anchors {

            top: stopHeader.top

            topMargin: Theme.paddingMedium

            bottom: stopHeader.bottom

            bottomMargin: Theme.paddingMedium

            left: towardsLabel.right

            leftMargin: Theme.paddingSmall

            right: favoriteButton.left

            rightMargin: Theme.paddingLarge

        }

    }


    Label {

        id: distanceLabel

        text: ""

        font.pixelSize: Theme.fontSizeExtraSmall

        color: Theme.highlightColor

        anchors {

            right: stopHeader.right

            bottom: stopHeader.bottom

        }

    }


    states: [


        State {

            name: "invisible"

            PropertyChanges {

                target: self

                opacity: 0

            }

            PropertyChanges {

                target: icon

                opacity: 0

            }

        },

        State {

            name: "visible"

            PropertyChanges {

                target: self

                opacity: 100

            }

            PropertyChanges {

                target: icon

                opacity: 100

            }

        }

    ]

    transitions: [

        Transition {

            from: "invisible"

            to: "visible"

            FadeAnimation {

                target: self

            }

        },

        Transition {

            from: "visible"

            to: "invisible"

            FadeAnimation {

                target: self

            }

        }

    ]

    onTitleChanged: { state = (title === "") ? "invisible" : "visible" }

}
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[D] ArrivalsLogic::stopArrivalsUpdate:468 - updating stopped. 
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
[W] unknown:72 - file:///usr/lib/qt5/qml/Sailfish/Silica/SearchField.qml:72: TypeError: Cannot read property 'activeFocus' of null
QSqlQuery::value: not positioned on a valid record
**** speed: -540
[W] unknown:51 - file:///opt/sdk/harbour-london-sail/usr/share/harbour-london-sail/qml/pages/BusStopPage.qml:51:5: QML Connections: Cannot assign to non-existent property "onDownloadSatateChanged"
**** speed: -960
[D] ArrivalsLogic::fetchArrivalsData:152 - updated 
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
[D] ArrivalsLogic::stopArrivalsUpdate:468 - updating stopped. 
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
**** speed: -540
[W] unknown:51 - file:///opt/sdk/harbour-london-sail/usr/share/harbour-london-sail/qml/pages/BusStopPage.qml:51:5: QML Connections: Cannot assign to non-existent property "onDownloadSatateChanged"
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 905.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 905.15625
[D] ArrivalsLogic::fetchArrivalsData:152 - updated 
[D] ArrivalsLogic::stopArrivalsUpdate:468 - updating stopped. 
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
**** speed: -540
[W] unknown:51 - file:///opt/sdk/harbour-london-sail/usr/share/harbour-london-sail/qml/pages/BusStopPage.qml:51:5: QML Connections: Cannot assign to non-existent property "onDownloadSatateChanged"
**** speed: -960
[D] ArrivalsLogic::fetchArrivalsData:152 - updated 
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
[D] ArrivalsLogic::fetchArrivalsData:152 - updated 
[D] ArrivalsLogic::stopArrivalsUpdate:468 - updating stopped. 
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
**** speed: -540
[W] unknown:51 - file:///opt/sdk/harbour-london-sail/usr/share/harbour-london-sail/qml/pages/BusStopPage.qml:51:5: QML Connections: Cannot assign to non-existent property "onDownloadSatateChanged"
**** speed: -960
[D] ArrivalsLogic::fetchArrivalsData:152 - updated 
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
[W] unknown:-1 - file:///usr/lib/qt5/qml/Sailfish/Silica/private/HighlightImage.qml: RangeError: Maximum call stack size exceeded
**** speed: 485.15625
QQmlComponent: Cannot create new component instance before completing the previous
Remote application crashed: Process killed by signal