ChartDirector 6.0 (C++ Edition)

Simple Zooming and Scrolling (QT)

NOTE: This section describes Simple Zooming and Scrolling for QT only. For MFC, please refer to Simple Zooming and Scrolling (MFC).

This sample program demonstrates simple zoomable and scrollable chart with tooltips, using mouse click and drag to control zooming and scrolling.

The main source code listing of this sample program is included at the end of this section. The code consists of the following main parts:

Source Code Listing

The following is the main source code of this demo. The complete QT project is in "qtdemo/simplezoomscroll".

[File: qtdemo/simplezoomscroll/simplezoomscroll.cpp]
#include <QApplication>
#include <QPushButton>
#include <QButtonGroup>
#include <math.h>
#include "simplezoomscroll.h"

int main(int argc, char *argv[])
    QApplication app(argc, argv);
    app.setStyleSheet("* {font-family:arial;font-size:11px}");
    SimpleZoomScroll demo;;
    return app.exec();

SimpleZoomScroll::SimpleZoomScroll(QWidget *parent) :
    // Set up the GUI

    setFixedSize(732, 308);
    setWindowTitle("Simple Zooming and Scrolling");

    // The frame on the left side
    QFrame *frame = new QFrame(this);
    frame->setGeometry(4, 4, 120, 300);

    // Pointer push button
    QPushButton *pointerPB = new QPushButton(QIcon(":/pointer.png"), "Pointer", frame);
    pointerPB->setGeometry(4, 8, 112, 28);
    pointerPB->setStyleSheet("QPushButton { text-align:left; padding:5px}");

    // Zoom In push button
    QPushButton *zoomInPB = new QPushButton(QIcon(":/zoomin.png"), "Zoom In", frame);
    zoomInPB->setGeometry(4, 36, 112, 28);
    zoomInPB->setStyleSheet("QPushButton { text-align:left; padding:5px}");

    // Zoom Out push button
    QPushButton *zoomOutPB = new QPushButton(QIcon(":/zoomout.png"), "Zoom Out", frame);
    zoomOutPB->setStyleSheet("QPushButton { text-align:left; padding:5px}");
    zoomOutPB->setGeometry(4, 64, 112, 28);

    // The Pointer/Zoom In/Zoom Out buttons form a button group
    QButtonGroup *mouseUsage = new QButtonGroup(frame);
    mouseUsage->addButton(pointerPB, Chart::MouseUsageScroll);
    mouseUsage->addButton(zoomInPB, Chart::MouseUsageZoomIn);
    mouseUsage->addButton(zoomOutPB, Chart::MouseUsageZoomOut);
    connect(mouseUsage, SIGNAL(buttonPressed(int)), SLOT(onMouseUsageChanged(int)));

    // Chart Viewer
    m_ChartViewer = new QChartViewer(this);
    m_ChartViewer->setGeometry(128, 4, 650, 350);
    connect(m_ChartViewer, SIGNAL(viewPortChanged()), SLOT(onViewPortChanged()));
    connect(m_ChartViewer, SIGNAL(mouseMovePlotArea(QMouseEvent*)), SLOT(onMouseMovePlotArea(QMouseEvent*)));
    connect(m_ChartViewer, SIGNAL(mouseWheel(QWheelEvent*)), SLOT(onMouseWheelChart(QWheelEvent*)));

    // Initialize the chart

    // Load the data

    // Initialize the QChartViewer

    // Initially set the mouse to drag to scroll mode

    // Trigger the ViewPortChanged event to draw the chart
    m_ChartViewer->updateViewPort(true, true);

    delete m_ranSeries;
    delete m_ChartViewer->getChart();

// Load the data
void SimpleZoomScroll::loadData()
    // In this example, we just use random numbers as data.
    m_ranSeries = new RanSeries(127);
    m_timeStamps = m_ranSeries->getDateSeries(1827, Chart::chartTime(2007, 1, 1), 86400);
    m_dataSeriesA = m_ranSeries->getSeries(1827, 150, -10, 10);
    m_dataSeriesB = m_ranSeries->getSeries(1827, 200, -10, 10);
    m_dataSeriesC = m_ranSeries->getSeries(1827, 250, -8, 8);

// Initialize the QChartViewer
void SimpleZoomScroll::initChartViewer(QChartViewer *viewer)
    // Set the full x range to be the duration of the data
    viewer->setFullRange("x", m_timeStamps[0], m_timeStamps[m_timeStamps.len - 1]);

    // Initialize the view port to show the latest 20% of the time range
    viewer->setViewPortLeft(1 - viewer->getViewPortWidth());

    // Set the maximum zoom to 10 points
    viewer->setZoomInWidthLimit(10.0 / m_timeStamps.len);

// The ViewPortChanged event handler. This event occurs if the user scrolls or zooms in
// or out the chart by dragging or clicking on the chart. It can also be triggered by
// calling WinChartViewer.updateViewPort.
void SimpleZoomScroll::onViewPortChanged()
    if (m_ChartViewer->needUpdateChart())
    if (m_ChartViewer->needUpdateImageMap())

// Draw the chart and display it in the given viewer
void SimpleZoomScroll::drawChart(QChartViewer *viewer)
    // Get the start date and end date that are visible on the chart.
    double viewPortStartDate = viewer->getValueAtViewPort("x", viewer->getViewPortLeft());
    double viewPortEndDate = viewer->getValueAtViewPort("x", viewer->getViewPortLeft() +

    // Get the array indexes that corresponds to the visible start and end dates
    int startIndex = (int)floor(Chart::bSearch(m_timeStamps, viewPortStartDate));
    int endIndex = (int)ceil(Chart::bSearch(m_timeStamps, viewPortEndDate));
    int noOfPoints = endIndex - startIndex + 1;

    // Extract the part of the data array that are visible.
    DoubleArray viewPortTimeStamps = DoubleArray( + startIndex, noOfPoints);
    DoubleArray viewPortDataSeriesA = DoubleArray( + startIndex, noOfPoints);
    DoubleArray viewPortDataSeriesB = DoubleArray( + startIndex, noOfPoints);
    DoubleArray viewPortDataSeriesC = DoubleArray( + startIndex, noOfPoints);

    // At this stage, we have extracted the visible data. We can use those data to plot the chart.

    // Configure overall chart appearance.

    // Create an XYChart object 600 x 300 pixels in size, with pale blue (0xf0f0ff) background,
    // black (000000) rounded border, 1 pixel raised effect.
    XYChart *c = new XYChart(600, 300, 0xf0f0ff, 0, 1);
    QColor bgColor = palette().color(backgroundRole()).rgb();
    c->setRoundedFrame(( << 16) + ( << 8) +;

    // Set the plotarea at (52, 60) and of size 520 x 205 pixels. Use white (ffffff) background.
    // Enable both horizontal and vertical grids by setting their colors to grey (cccccc). Set
    // clipping mode to clip the data lines to the plot area.
    c->setPlotArea(52, 60, 520, 205, 0xffffff, -1, -1, 0xcccccc, 0xcccccc);

    // As the data can lie outside the plotarea in a zoomed chart, we need to enable clipping.

    // Add a top title to the chart using 15 pts Times New Roman Bold Italic font, with a light blue
    // (ccccff) background, black (000000) border, and a glass like raised effect.
    c->addTitle("Simple Zooming and Scrolling", "timesbi.ttf", 15
        )->setBackground(0xccccff, 0x0, Chart::glassEffect());

    // Add a legend box at the top of the plot area with 9pts Arial Bold font with flow layout.
    c->addLegend(50, 33, false, "arialbd.ttf", 9)->setBackground(Chart::Transparent, Chart::Transparent);

    // Set axes width to 2 pixels

    // Add a title to the y-axis
    c->yAxis()->setTitle("Price (USD)", "arialbd.ttf", 9);

    // Add data to chart

    // In this example, we represent the data by lines. You may modify the code below to use other
    // representations (areas, scatter plot, etc).

    // Add a line layer for the lines, using a line width of 2 pixels
    LineLayer *layer = c->addLineLayer();

    // In this demo, we do not have too many data points. In real code, the chart may contain a lot
    // of data points when fully zoomed out - much more than the number of horizontal pixels in this
    // plot area. So it is a good idea to use fast line mode.

    // Now we add the 3 data series to a line layer, using the color red (ff0000), green
    // (00cc00) and blue (0000ff)
    layer->addDataSet(viewPortDataSeriesA, 0xff0000, "Product Alpha");
    layer->addDataSet(viewPortDataSeriesB, 0x00cc00, "Product Beta");
    layer->addDataSet(viewPortDataSeriesC, 0x0000ff, "Product Gamma");

    // Configure axis scale and labelling

    // Set the x-axis as a date/time axis with the scale according to the view port x range.
    viewer->syncDateAxisWithViewPort("x", c->xAxis());

    // In this demo, we rely on ChartDirector to auto-label the axis. We ask ChartDirector to ensure
    // the x-axis labels are at least 75 pixels apart to avoid too many labels.

    // Output the chart

    delete viewer->getChart();

// Update the image map
void SimpleZoomScroll::updateImageMap(QChartViewer *viewer)
    // Include tool tip for the chart
    if (0 == viewer->getImageMapHandler())
        viewer->setImageMap(viewer->getChart()->getHTMLImageMap("", "",
            "title='[{dataSetName}] {x|mmm dd, yyyy}: USD {value|2}'"));

// The Pointer, Zoom In or Zoom out button is pressed
void SimpleZoomScroll::onMouseUsageChanged(int mouseUsage)