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Details

Type: Bug
Resolution: Fixed
Priority: P3: Somewhat important
Fix Version/s: 5.15.3, 5.15.5, 6.1.1, 6.2.0 Alpha
Affects Version/s: 5.8.0, 5.12.7, 5.15.0
Component/s: Charts
Labels:
- Reported_by_support_2H20
- Reported_by_support_standard
Environment:
Ubuntu 16.04 and Android

Commits:
d3b5b6c24ae47eaa19d426ff428b8e0f58d4678c e292cd6249b347771006aa9bbeef735391e367ac 1fb4a3ef2bd86d650495e15a23c7efc1e600a59a

Description

The performance of an entire QML application grinds to a halt when changing the min/max values of a ValueAxis in a ChartView often. We have multiple charts where we need to dynamically change these values as data is updated and this seems to be an issue for all of them.

Here is a snippet of code where this issue occurs:

ChartView {
    id: chartView
    anchors.fill: parent
    legend.visible: false
    antialiasing: true
    backgroundColor: "transparent"
    enabled: false // disables mouse input
    margins.top: 0
    margins.bottom: 0
    margins.left: 10
    margins.right: 0

    LineSeries {
        id: series
        axisX: axisX
        axisY: axisY
        color: chartItem.lineColor
        width: 2.0
    }

    LineSeries {
        id: fireSeries
        axisX: axisX
        axisY: axisY
        color: chartItem.lineColor
        width: 2.0
    }

    ValueAxis {
        id: axisX
        min: voltmeterRoot.minimumTime
        max: voltmeterRoot.maximumTime
        tickCount: 2
        gridVisible: false
        labelsVisible: false
        lineVisible: showAxis
    }

    ValueAxis {
        id: axisY
        min: voltmeterRoot.minimumValue
        max: voltmeterRoot.maximumValue
        tickCount: 2
        gridVisible: false
        labelsVisible: false
        lineVisible: showAxis
    }
}

The points of the LineSeries are added dynamically, but the performance is degraded even when no points are added to the LineSeries. It is enough to spam changes to the min/max values of the ValueAxis.

This issue does not occur in previous versions of QtCharts. We have tested the same code with Qt 5.7.0 and Qt 5.7.1 without issues.