GUI freezing despite using incubateObject

alexcrist

Hello,

I'm using QML Shape and ShapePath to draw a basic chart. This works just fine with a few tens or hundreds of items. But my model can sometimes contain more than 10-12.000 items.

The code looks like this:

Shape {
    property var item

    anchors.fill: parent
    asynchronous: true

    ShapePath {
        id: path
        startX: 0
        startY: parent.height
    }

    onItemChanged: {
        var elements = [];
        var currentTrack = item.track;
        var maxSpeed = item.maxSpeed.value + 10;

        for (var i = 0; i < currentTrack.length; i++)
        {
            var point = currentTrack[i];
            var pathLine = Qt.createQmlObject('import QtQuick 2.15; PathLine {}', speedPath);

            pathLine.x = speedChart.width / (currentTrack.length - 1) * i;
            pathLine.y = speedChart.height - (speedChart.height / maxSpeed * point.speed.value);
            elements.push(pathLine);
        }

        path.pathElements = elements;
    }
}

The code works fine placed either on the QML page itself, either created using an incubator like so:

var shapeFactory = Qt.createComponent("shape.qml");
            chart.data = [];
            var incubator = shapeFactory.incubateObject(chart, { item: <some_item> }, Qt.Asynchronous);

            if (incubator.status !== Component.Ready)
            {
                incubator.onStatusChanged = function(status) {
                    if (status === Component.Ready)
                    {
                        console.log("done!");
                        chart.data.push(incubator.object);
                    }
                }
            } else {
                chart.data.push(incubator.object);
            }

However, both approaches lead to GUI freezes for 12 seconds (without the incubator), and 8 seconds (with the incubator), for a data set of 12.000 points.

The slight improvement offered by the incubator doesn't make sense to me. Shouldn't everything be done async? What am I missing or doing wrong about it? :(

Thanks!