DropShadow in Qml application causes Debug error. Reproducable 100%

[avkn]

Several days ago I got a "Debug error!" message box while running a QtQuick application, and the following message in Application output:

ASSERT failure in QVector<T>::at: "index out of range", file c:\work\build\qt5_workdir\w\s\qtbase\include\qtcore../../src/corelib/tools/qvector.h, line 393

It took a couple of hours to find out, that it is a DropShadow graphic effect, that cause this issue.

Here is my "minimal application" (only qml files) that reproduces this case. This is a Qt Quick Application project.

main.qml:

import QtQuick 2.3
import QtQuick.Window 2.2

Window {
    id: root
    visible: true

    property int count: 0

    Text {
        id: text
        text: qsTr("loop count: ") + count
        anchors.horizontalCenter: parent
        anchors.top: parent.top
        anchors.topMargin: 10
    }
    Loader {
        id: loader
        anchors.top: text.bottom
        width: root.width
        height: root.height - text.height - 10
        source: "qrc:/one.qml"
    }

    Connections {
        target: loader.item
        onOne:{
            loader.source = "qrc:/two.qml"
        }
        onTwo: {
            loader.source = "qrc:/one.qml"
            count++
        }
    }
}

one.qml:

import QtQuick 2.0
import QtGraphicalEffects 1.0

Item {
    id: root
    signal one ()

    Timer {
        interval: 1000; running: true; repeat: false
        onTriggered: root.one()
    }

    Rectangle {
        id: rect
        width: 100
        height: 100
        anchors.centerIn: root
        color: "red"
        border.color: "black"
        border.width: 3
        radius: 10
    }
    DropShadow {
         anchors.fill: rect
         horizontalOffset: 3
         verticalOffset: 3
         samples: 7
         color: "#80000000"
         source: rect
     }
}

The two.qml file is the same as the one.qml, it differs only in three lines:

signal one () -> signal two ()
onTriggered: root.one() -> onTriggered: root.two ()
color: "red" -> color: "green"

I get error messages short after start.
You can experiment, commenting out DropShadow in one.qml, in two.qml, in both. If you comment out both, the application runs infinite.

My environment:

Qt Creator 3.6.0
Based on Qt 5.5.1 (MSVC 2013, 32 bit)
Built on Dec 15 2015 01:01:38
From revision b52c2f91f5

Kit: Desktop Qt 5.5.1 MSVC2010 32 bit

Maybe someone knows what is happening there, and how can I use DropShadow without this errors?
Thank you in advance!

[SGaist]

Hi,

You should check against a more recent version of Qt to see if it's still reproducible (5.6.1 or 5.7.0). If so then you should take a look a the bug report system to see if it something known. If not please consider opening a new report providing your sample application.

[avkn]

@SGaist

Thank you for your advice.
Have changed to 5.7.0/MS VS 2015, no "Debug error!" enymore. But now it looks the same as if there were no DropShadow at all. I can not see any shadow.

[SGaist]

You may have found a bug then. You should check the bug report system to see if it's something known. If not please consider opening a new report with your sample application.