- Qt 5.15
- Qt Charts
- Qt Charts Examples
- Qml F1 Legends
- Qt Charts | Commercial or GPLv3

# Qml F1 Legends

This application demonstrates how to use XmlListModel as a datasource for a Chart.

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

#### Using List Models as Data Sources

Let's define an empty ChartView first:

     ChartView {
         id: chartView
         title: "Driver Speeds, lap 1"
         anchors.fill: parent
         legend.alignment: Qt.AlignTop
         animationOptions: ChartView.SeriesAnimations
         antialiasing: true
     }

Our XmlListModel uses hard-coded test data. In a real application the data source would be a timing system.

     XmlListModel {
         // Hard-coded test data
         xml: "<results><row><speedTrap>0</speedTrap><driver>Fittipaldi</driver><speed>104.12</speed></row>"
             +"<row><speedTrap>0</speedTrap><driver>Stewart</driver><speed>106.12</speed></row>"
             +"<row><speedTrap>0</speedTrap><driver>Hunt</driver><speed>106.12</speed></row>"
         ...
         query: "/results/row"

         XmlRole { name: "speedTrap"; query: "speedTrap/string()" }
         XmlRole { name: "driver"; query: "driver/string()" }
         XmlRole { name: "speed"; query: "speed/string()" }
     }
     // An example XmlListModel containing F1 legend drivers' speeds at speed traps
     SpeedsXml {
         id: speedsXml
         onStatusChanged: {
             if (status == XmlListModel.Ready) {
                 timer.start();
             }
         }
     }

The data is parsed with a timer. The line series representing each driver are created on the fly.

     // A timer to mimic refreshing the data dynamically
     Timer {
         id: timer
         interval: 700
         repeat: true
         triggeredOnStart: true
         running: false
         onTriggered: {
             currentIndex++;
             if (currentIndex < speedsXml.count) {
                 // Check if there is a series for the data already
                 // (we are using driver name to identify series)
                 var lineSeries = chartView.series(speedsXml.get(currentIndex).driver);
                 if (!lineSeries) {
                     lineSeries = chartView.createSeries(ChartView.SeriesTypeLine,
                                                         speedsXml.get(currentIndex).driver);
                     chartView.axisY().min = 0;
                     chartView.axisY().max = 250;
                     chartView.axisY().tickCount = 6;
                     chartView.axisY().titleText = "speed (kph)";
                     chartView.axisX().titleText = "speed trap";
                     chartView.axisX().labelFormat = "%.0f";
                 }
                 lineSeries.append(speedsXml.get(currentIndex).speedTrap,
                                   speedsXml.get(currentIndex).speed);

                 if (speedsXml.get(currentIndex).speedTrap > 3) {
                     chartView.axisX().max = Number(speedsXml.get(currentIndex).speedTrap) + 1;
                     chartView.axisX().min = chartView.axisX().max - 5;
                 } else {
                     chartView.axisX().max = 5;
                     chartView.axisX().min = 0;
                 }
                 chartView.axisX().tickCount = chartView.axisX().max - chartView.axisX().min + 1;
             } else {
                 // No more data, change x-axis range to show all the data
                 timer.stop();
                 chartView.animationOptions = ChartView.AllAnimations;
                 chartView.axisX().min = 0;
                 chartView.axisX().max = speedsXml.get(currentIndex - 1).speedTrap;
             }
         }
     }

Example project @ code.qt.io