QScatterSeries + QChartView scaling issue

[ZNohre]

All,

I'm running into (what I assume is) a novice issue when adding some charts to the dashboard of my desktop app.

When running tests with QScatterSeries with a QDateTimeAxis (X) and QValueAxis (Y) the default axis scaling is putting the oldest and newest points right in the corners of the chart. Is there a preferred method of more appropriately displaying these points (i.e. with some padding to the X- and Y-axis)?

Reviewing the documentation for QChart and QScatterSeries I tried chart->zoomOut() to no avail. I also saw setMin(const QDateTime &min) and setMax(const QDateTime &max) but wasn't sure if this needed to be added manually, or if there was a more elegant solution?

    QChartView *chartView = new QChartView(this);
    chartView->chart()->setTitle("Chart Title");

    QScatterSeries *series = new QScatterSeries(chartView->chart());
    series->setName("Series A");
    series->setMarkerShape(QScatterSeries::MarkerShapeStar);

    QDateTime dateTime1 = QDateTime::fromString("2024-01-15 10:00:00", "yyyy-MM-dd hh:mm:ss");
    QDateTime dateTime2 = QDateTime::fromString("2024-01-16 14:30:00", "yyyy-MM-dd hh:mm:ss");
    QDateTime dateTime3 = QDateTime::fromString("2024-01-17 14:30:00", "yyyy-MM-dd hh:mm:ss");

    series->append(dateTime1.toMSecsSinceEpoch(), 15);
    series->append(dateTime2.toMSecsSinceEpoch(), 25);
    series->append(dateTime3.toMSecsSinceEpoch(), 35);

    chartView->chart()->addSeries(series);

    //X axis
    QDateTimeAxis *axisX = new QDateTimeAxis();
    axisX->setFormat("yyyy-MM-dd hh:mm");
    chartView->chart()->addAxis(axisX, Qt::AlignBottom);
    series->attachAxis(axisX);

    //Y axis
    QValueAxis *axisY = new QValueAxis();
    chartView->chart()->addAxis(axisY, Qt::AlignLeft);
    series->attachAxis(axisY);

    ui->chartGroup1->layout()->addWidget(chartView);

Thanks

[ZNohre]

Maybe there is a more elegant solution out there but after some more digging I ended up implementing a simple min/max call here for each axis which is working fine.

    //Axis margins
    int x = 5;
    int y = 5;

    //X axis margin
    axisX->setMin(axisX->min().addDays(-x));
    axisX->setMax(axisX->max().addDays(x));

    //Y axis margin
    axisY->setMin(axisY->min()-y);
    axisY->setMax(axisY->max()+y);

[A.A.SEZEN]

I use the same method to place candles. I considered sharing it for you, but I decided against it because it might be a more practical solution or might be too complicated. I'm sharing it for variety and to provide the code, as I use it.

   auto axis = dynamic_cast<QDateTimeAxis *>(a);
   QDateTime min, max; 
   const unsigned long long imsec = classes->settingsManager->intervalMsec(klines->interval()) / 2;
   using namespace std::chrono;
   time_t timeLast = (static_cast<long>(klines->lastDate() + imsec)) / 1000;
   time_t timeFirst = (static_cast<long>(klines->firstDate() + imsec)) / 1000;
   min = QDateTime::fromString(ctime(&timeFirst));
   max = QDateTime::fromString(ctime(&timeLast));
   if (min != axis->min() || max != axis->max()) {
       axis->setMin(min);
       axis->setMax(max);
       axis->setRange(min, max);
   }