ChartDirector 6.0 (C++ Edition)

Zooming and Scrolling with Track Line (1) (QT)




NOTE: This section describes Zooming and Scrolling with Track Line (1) for QT only. For MFC, please refer to Zooming and Scrolling with Track Line (1) (MFC).

In addition to using mouse click and drag, this example demonstrates using a scroll bar for scrolling and mouse wheel for zooming. It also includes a track cursor that updates the legend dynamically to display the data values as the mouse cursor moves over the chart.

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/zoomscrolltrack".

[File: qtdemo/zoomscrolltrack/zoomscrolltrack.cpp]
#include <QApplication>
#include <QPushButton>
#include <QButtonGroup>
#include <QMouseEvent>
#include <math.h>
#include <sstream>
#include <algorithm>
#include "zoomscrolltrack.h"

using namespace std;


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

ZoomScrollTrack::ZoomScrollTrack(QWidget *parent) :
    QDialog(parent)
{
    //
    // Set up the GUI
    //

    setFixedSize(782, 376);
    setWindowTitle("Zooming and Scrolling with Track Line (1)");

    // The frame on the left side
    QFrame *frame = new QFrame(this);
    frame->setGeometry(4, 4, 120, 370);
    frame->setFrameShape(QFrame::StyledPanel);

    // 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}");
    pointerPB->setCheckable(true);

    // 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}");
    zoomInPB->setCheckable(true);

    // 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);
    zoomOutPB->setCheckable(true);

    // 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*)));

    // Horizontal scroll bar
    m_HScrollBar = new QScrollBar(Qt::Horizontal, this);
    m_HScrollBar->setGeometry(128, 356, 650, 17);
    connect(m_HScrollBar, SIGNAL(valueChanged(int)), SLOT(onHScrollBarChanged(int)));

    //
    // Initialize the chart
    //

    // Load the data
    loadData();

    // Initialize the QChartViewer
    initChartViewer(m_ChartViewer);

    // Initially set the mouse to drag to scroll mode
    pointerPB->click();

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

ZoomScrollTrack::~ZoomScrollTrack()
{
    delete m_ranSeries;
    delete m_ChartViewer->getChart();
}

//
// Load the data
//
void ZoomScrollTrack::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 ZoomScrollTrack::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->setViewPortWidth(0.2);
    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 ZoomScrollTrack::onViewPortChanged()
{
    // In addition to updating the chart, we may also need to update other controls that
    // changes based on the view port.
    updateControls(m_ChartViewer);

    // Update chart if necessary
    if (m_ChartViewer->needUpdateChart())
        drawChart(m_ChartViewer);
}

//
// Update controls in the user interface when the view port changed
//
void ZoomScrollTrack::updateControls(QChartViewer *viewer)
{
    // The logical length of the scrollbar. It can be any large value. The actual value does
    // not matter.
    const int scrollBarLen = 1000000000;

    // Update the horizontal scroll bar
    m_HScrollBar->setEnabled(viewer->getViewPortWidth() < 1);
    m_HScrollBar->setPageStep((int)ceil(viewer->getViewPortWidth() * scrollBarLen));
    m_HScrollBar->setSingleStep(min(scrollBarLen / 100, m_HScrollBar->pageStep()));
    m_HScrollBar->setRange(0, scrollBarLen - m_HScrollBar->pageStep());
    m_HScrollBar->setValue((int)(0.5 + viewer->getViewPortLeft() * scrollBarLen));
}

//
// Draw the chart and display it in the given viewer
//
void ZoomScrollTrack::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() +
        viewer->getViewPortWidth());

    // 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(m_timeStamps.data + startIndex, noOfPoints);
    DoubleArray viewPortDataSeriesA = DoubleArray(m_dataSeriesA.data + startIndex, noOfPoints);
    DoubleArray viewPortDataSeriesB = DoubleArray(m_dataSeriesB.data + startIndex, noOfPoints);
    DoubleArray viewPortDataSeriesC = DoubleArray(m_dataSeriesC.data + 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 of size 650 x 350 pixels, with a white (ffffff) background and grey
    // (aaaaaa) border
    XYChart *c = new XYChart(650, 350, 0xffffff, 0xaaaaaa);

    // Set the plotarea at (55, 55) with width 90 pixels less than chart width, and height 90 pixels
    // less than chart height. Use a vertical gradient from light blue (f0f6ff) to sky blue (a0c0ff)
    // as background. Set border to transparent and grid lines to white (ffffff).
    c->setPlotArea(55, 55, c->getWidth() - 90, c->getHeight() - 90, c->linearGradientColor(0, 55, 0,
        c->getHeight() - 35, 0xf0f6ff, 0xa0c0ff), -1, Chart::Transparent, 0xffffff, 0xffffff);

    // As the data can lie outside the plotarea in a zoomed chart, we need enable clipping.
    c->setClipping();

    // Add a title to the chart using 18 pts Times New Roman Bold Italic font
    c->addTitle("   Zooming and Scrolling with Track Line (1)", "timesbi.ttf", 18);

    // Set legend icon style to use line style icon, sized for 8pt font
    c->getLegend()->setLineStyleKey();
    c->getLegend()->setFontSize(8);

    // Set the axis stem to transparent
    c->xAxis()->setColors(Chart::Transparent);
    c->yAxis()->setColors(Chart::Transparent);

    // Add axis title using 10pts Arial Bold Italic font
    c->yAxis()->setTitle("Ionic Temperature (C)", "arialbi.ttf", 10);

    ///////////////////////////////////////////////////////////////////////////////////////
    // 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();
    layer->setLineWidth(2);

    // 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.
    layer->setFastLineMode();

    // Now we add the 3 data series to a line layer, using the color red (ff0000), green
    // (00cc00) and blue (0000ff)
    layer->setXData(viewPortTimeStamps);
    layer->addDataSet(viewPortDataSeriesA, 0xff3333, "Alpha");
    layer->addDataSet(viewPortDataSeriesB, 0x008800, "Beta");
    layer->addDataSet(viewPortDataSeriesC, 0x3333CC, "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, the time range can be from a few years to a few days. We demonstrate how to set
    // up different date/time format based on the time range.
    //

    // If all ticks are yearly aligned, then we use "yyyy" as the label format.
    c->xAxis()->setFormatCondition("align", 360 * 86400);
    c->xAxis()->setLabelFormat("{value|yyyy}");

    // If all ticks are monthly aligned, then we use "mmm yyyy" in bold font as the first
    // label of a year, and "mmm" for other labels.
    c->xAxis()->setFormatCondition("align", 30 * 86400);
    c->xAxis()->setMultiFormat(Chart::StartOfYearFilter(), "<*font=bold*>{value|mmm yyyy}",
        Chart::AllPassFilter(), "{value|mmm}");

    // If all ticks are daily algined, then we use "mmm dd<*br*>yyyy" in bold font as the
    // first label of a year, and "mmm dd" in bold font as the first label of a month, and
    // "dd" for other labels.
    c->xAxis()->setFormatCondition("align", 86400);
    c->xAxis()->setMultiFormat(Chart::StartOfYearFilter(),
        "<*block,halign=left*><*font=bold*>{value|mmm dd<*br*>yyyy}",
        Chart::StartOfMonthFilter(), "<*font=bold*>{value|mmm dd}");
    c->xAxis()->setMultiFormat(Chart::AllPassFilter(), "{value|dd}");

    // For all other cases (sub-daily ticks), use "hh:nn<*br*>mmm dd" for the first label of
    // a day, and "hh:nn" for other labels.
    c->xAxis()->setFormatCondition("else");
    c->xAxis()->setMultiFormat(Chart::StartOfDayFilter(),
        "<*font=bold*>{value|hh:nn<*br*>mmm dd}", Chart::AllPassFilter(), "{value|hh:nn}");

    ///////////////////////////////////////////////////////////////////////////////////////
    // Output the chart
    ///////////////////////////////////////////////////////////////////////////////////////

    // We need to update the track line too. If the mouse is moving on the chart (eg. if 
    // the user drags the mouse on the chart to scroll it), the track line will be updated
    // in the MouseMovePlotArea event. Otherwise, we need to update the track line here.
    if (!viewer->isInMouseMoveEvent()) 
    {
        trackLineLegend(c, (0 == viewer->getChart()) ? c->getPlotArea()->getRightX() :
            viewer->getPlotAreaMouseX()); 
    }

    delete viewer->getChart();
    viewer->setChart(c);
}

//
// The Pointer, Zoom In or Zoom out button is pressed
//
void ZoomScrollTrack::onMouseUsageChanged(int mouseUsage)
{
    m_ChartViewer->setMouseUsage(mouseUsage);
}

//
// User clicks on the the horizontal scroll bar
//
void ZoomScrollTrack::onHScrollBarChanged(int value)
{
    if (!m_ChartViewer->isInViewPortChangedEvent())
    {
        // Set the view port based on the scroll bar
        int scrollBarLen = m_HScrollBar->maximum() + m_HScrollBar->pageStep();
        m_ChartViewer->setViewPortLeft(value / (double)scrollBarLen);

        // Update the chart display without updating the image maps. (We can delay updating
        // the image map until scrolling is completed and the chart display is stable.)
        m_ChartViewer->updateViewPort(true, false);
    }
}

//
// When the mouse enters the chart, we will generate an image map for hot spots and tooltips
// support if it has not already been generated.
//
void ZoomScrollTrack::onMouseWheelChart(QWheelEvent *event)
{
    // Process the mouse wheel only if the mouse is over the plot area
    if (!m_ChartViewer->isMouseOnPlotArea())
    {
        event->ignore();
        return;
    }

    // We zoom in or out by 10% depending on the mouse wheel direction.
    double newVpWidth = m_ChartViewer->getViewPortWidth() * (event->delta() > 0 ? 0.9 : 1 / 0.9);
    double newVpHeight = m_ChartViewer->getViewPortHeight() * (event->delta() > 0 ? 0.9 : 1 / 0.9);

    // We do not zoom beyond the zoom width or height limits.
    newVpWidth = max(m_ChartViewer->getZoomInWidthLimit(), min(newVpWidth,
        m_ChartViewer->getZoomOutWidthLimit()));
    newVpHeight = max(m_ChartViewer->getZoomInHeightLimit(), min(newVpWidth,
        m_ChartViewer->getZoomOutHeightLimit()));

    if ((newVpWidth != m_ChartViewer->getViewPortWidth()) ||
            (newVpHeight != m_ChartViewer->getViewPortHeight()))
    {
        // Set the view port position and size so that the point under the mouse remains under
        // the mouse after zooming.

        double deltaX = (m_ChartViewer->getPlotAreaMouseX() - m_ChartViewer->getPlotAreaLeft()) *
            (m_ChartViewer->getViewPortWidth() - newVpWidth) / m_ChartViewer->getPlotAreaWidth();
        m_ChartViewer->setViewPortLeft(m_ChartViewer->getViewPortLeft() + deltaX);
        m_ChartViewer->setViewPortWidth(newVpWidth);

        double deltaY = (m_ChartViewer->getPlotAreaMouseY() - m_ChartViewer->getPlotAreaTop()) *
            (m_ChartViewer->getViewPortHeight() - newVpHeight) / m_ChartViewer->getPlotAreaHeight();
        m_ChartViewer->setViewPortTop(m_ChartViewer->getViewPortTop() + deltaY);
        m_ChartViewer->setViewPortHeight(newVpHeight);

        m_ChartViewer->updateViewPort(true, false);
    }
}

//
// Draw track cursor when mouse is moving over plotarea
//
void ZoomScrollTrack::onMouseMovePlotArea(QMouseEvent *)
{
    trackLineLegend((XYChart *)m_ChartViewer->getChart(), m_ChartViewer->getPlotAreaMouseX());
    m_ChartViewer->updateDisplay();
}

//
// Draw track line with data labels
//
void ZoomScrollTrack::trackLineLegend(XYChart *c, int mouseX)
{
    // Clear the current dynamic layer and get the DrawArea object to draw on it.
    DrawArea *d = c->initDynamicLayer();

    // The plot area object
    PlotArea *plotArea = c->getPlotArea();

    // Get the data x-value that is nearest to the mouse, and find its pixel coordinate.
    double xValue = c->getNearestXValue(mouseX);
    int xCoor = c->getXCoor(xValue);

    // Draw a vertical track line at the x-position
    d->vline(plotArea->getTopY(), plotArea->getBottomY(), xCoor, d->dashLineColor(0x000000, 0x0101));

    // Container to hold the legend entries
    vector<string> legendEntries;

    // Iterate through all layers to build the legend array
    for (int i = 0; i < c->getLayerCount(); ++i) {
        Layer *layer = c->getLayerByZ(i);

        // The data array index of the x-value
        int xIndex = layer->getXIndexOf(xValue);

        // Iterate through all the data sets in the layer
        for (int j = 0; j < layer->getDataSetCount(); ++j) {
            DataSet *dataSet = layer->getDataSetByZ(j);

            // We are only interested in visible data sets with names
            const char *dataName = dataSet->getDataName();
            int color = dataSet->getDataColor();
            if (dataName && *dataName && (color != (int)Chart::Transparent)) {
                // Build the legend entry, consist of the legend icon, name and data value.
                double dataValue = dataSet->getValue(xIndex);
                ostringstream legendEntry;
                legendEntry << "<*block*>" << dataSet->getLegendIcon() << " " << dataName << ": " <<
                    ((dataValue == Chart::NoValue) ? "N/A" : c->formatValue(dataValue, "{value|P4}"))
                    << "<*/*>";
                legendEntries.push_back(legendEntry.str());

                // Draw a track dot for data points within the plot area
                int yCoor = c->getYCoor(dataSet->getPosition(xIndex), dataSet->getUseYAxis());
                if ((yCoor >= plotArea->getTopY()) && (yCoor <= plotArea->getBottomY())) {
                    d->circle(xCoor, yCoor, 4, 4, color, color);
                }
            }
        }
    }

    // Create the legend by joining the legend entries
    ostringstream legendText;
    legendText << "<*block,maxWidth=" << plotArea->getWidth() << "*><*block*><*font=arialbd.ttf*>["
        << c->xAxis()->getFormattedLabel(xValue, "mmm dd, yyyy") << "]<*/*>";
    for (int i = ((int)legendEntries.size()) - 1; i >= 0; --i)
        legendText << "        " << legendEntries[i];

    // Display the legend on the top of the plot area
    TTFText *t = d->text(legendText.str().c_str(), "arial.ttf", 8);
    t->draw(plotArea->getLeftX() + 5, plotArea->getTopY() - 3, 0x000000, Chart::BottomLeft);
    t->destroy();
}