Controlling number of boxes in box plot with Qt Chart - qt

Question

I am trying to figure out how to control number of boxes (or box sets) in the box plot with Qt chart, and use scrollbar to scroll through the whole chart. It's similar to this example (http://www.advsofteng.com/doc/cdcppdoc/zoomscrolltrackqt.htm).
The code below is what I did, and it populates all the boxes in the chartview, no matter how many. I selected 'ScrollBarAsNeeded' for the vertical and horizontal scroll bar policies in Qt designer.
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QChartView>
#include <QBoxPlotSeries>
#include <QBoxSet>
#include <QValueAxis>
#include <QBarCategoryAxis>
#include <QtSql>
#include <QSqlDatabase>
#include <QSqlQuery>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");
db.setHostName("192.168.2.103");
db.setPort(5433);
db.setUserName("vorlket");
db.setPassword("K1156312j");
db.setDatabaseName("fxproj");
QBoxPlotSeries *bidaskSeries = new QBoxPlotSeries(this);
bidaskSeries->setName("bidask");
QStringList categories;
if (db.open())
{
QSqlQuery query;
if (query.exec("SELECT EXTRACT(YEAR FROM month), EXTRACT(MONTH FROM month), bid_low, bid_lowquartile, bid_median, bid_upquartile, bid_high FROM audusd.ts_month_quotebid ORDER BY month"))
{
while (query.next())
{
categories << query.value(0).toString() + "-" + query.value(1).toString();
QBoxSet *set = new QBoxSet();
set->setValue(QBoxSet::LowerExtreme, query.value(2).toDouble());
set->setValue(QBoxSet::LowerQuartile, query.value(3).toDouble());
set->setValue(QBoxSet::Median, query.value(4).toDouble());
set->setValue(QBoxSet::UpperQuartile, query.value(5).toDouble());
set->setValue(QBoxSet::UpperExtreme, query.value(6).toDouble());
bidaskSeries->append(set);
}
}
db.close();
}
QChart *chart = new QChart();
chart->legend()->hide();
chart->addSeries(bidaskSeries);
QBarCategoryAxis * axisX = new QBarCategoryAxis();
axisX->append(categories);
chart->addAxis(axisX, Qt::AlignBottom);
chart->setAxisX(axisX, bidaskSeries);
QValueAxis *axisY = new QValueAxis();
chart->addAxis(axisY, Qt::AlignLeft);
chart->setAxisY(axisY, bidaskSeries);
axisY->setRange(0.65, 1.15);
ui->chartview->setChart(chart);
ui->chartview->setRenderHint(QPainter::Antialiasing);
}
MainWindow::~MainWindow()
{
delete ui;
}

Answer 1

Maybe I need to use QGraphicsScene, instead of QChartView.
http://doc.qt.io/qt-5/qchartview.html#details:
QChartView is a standalone widget that can display charts. It does not require separate QGraphicsScene to work. If you want to display a chart in your existing QGraphicsScene, you need to use the QChart (or QPolarChart) class instead.
http://doc.qt.io/qt-5/qgraphicsscene.html#details:
The QGraphicsScene class provides a surface for managing a large number of 2D graphical items.
The class serves as a container for QGraphicsItems. It is used together with QGraphicsView for visualizing graphical items, such as lines, rectangles, text, or even custom items, on a 2D surface. QGraphicsScene is part of the Graphics View Framework.
QGraphicsScene also provides functionality that lets you efficiently determine both the location of items, and for determining what items are visible within an arbitrary area on the scene. With the QGraphicsView widget, you can either visualize the whole scene, or zoom in and view only parts of the scene.