ChartDirector 6.0 (C++ Edition)

XY Zooming and Scrolling (QT)




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

This example demonstrates zooming and scrolling in both horizontal and vertical directions. In addition to using mouse click and drag, this example demonstrates using a slider, the mouse wheel and a QViewPortControl to control scrolling and zooming. This example also includes a crosshair track cursor with dynamic labels on the x-axis and y-axis showing the mouse cursor position, and an image map for data point tooltips. A save button is included to save the chart in PNG, JPG, GIF, BMP, SVG or PDF.

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/xyzoomscroll".

[File: qtdemo/xyzoomscroll/xyzoomscroll.cpp]
#include <QApplication>
#include <QButtonGroup>
#include <QMouseEvent>
#include <QFileDialog>
#include "xyzoomscroll.h"
#include "hotspotdialog.h"
#include <sstream>
#include <algorithm>

using namespace std;


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


XYZoomScroll::XYZoomScroll(QWidget *parent) :
    QDialog(parent)
{
    setWindowTitle("XY Zooming and Scrolling");
    setFixedSize(644, 488);

    QFrame *frame = new QFrame(this);
    frame->setGeometry(4, 4, 120, 481);
    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->setGeometry(4, 64, 112, 28);
    zoomOutPB->setStyleSheet("QPushButton { text-align:left; padding:5px}");
    zoomOutPB->setCheckable(true);

    // Save push button
    QPushButton *savePB = new QPushButton(QIcon(":/save.png"), "Save", frame);
    savePB->setStyleSheet("QPushButton { text-align:left; padding:5px}");
    savePB->setGeometry(4, 120, 112, 28);
    connect(savePB, SIGNAL(clicked(bool)), SLOT(onSave(bool)));

    // 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)));

    // Zoom Mode label
    QLabel *zoomModeLabel = new QLabel("Zoom Level", frame);
    zoomModeLabel->setGeometry(6, 180, 110, 18);
    zoomModeLabel->setAlignment(Qt::AlignHCenter);

    // Zoom level bar
    m_ZoomBar = new QSlider(Qt::Horizontal, frame);
    m_ZoomBar->setGeometry(12, 205, 102, 41);
    m_ZoomBar->setRange(1, 100);
    m_ZoomBar->setTickPosition(QSlider::TicksBothSides);
    m_ZoomBar->setInvertedAppearance(true);
    connect(m_ZoomBar, SIGNAL(valueChanged(int)), SLOT(onZoomBarChanged(int)));

    // Viewport Control
    m_ViewPortControl = new QViewPortControl(frame);
    m_ViewPortControl->setGeometry(QRect(5, 334, 112, 112));

    // Chart Viewer
    m_ChartViewer = new QChartViewer(this);
    m_ChartViewer->setGeometry(QRect(136, 4, 500, 480));
    connect(m_ChartViewer, SIGNAL(viewPortChanged()), SLOT(onViewPortChanged()));
    connect(m_ChartViewer, SIGNAL(mouseMovePlotArea(QMouseEvent*)), SLOT(onMouseMovePlotArea(QMouseEvent*)));
    connect(m_ChartViewer, SIGNAL(clicked(QMouseEvent*)), SLOT(onClickChart(QMouseEvent*)));

    //
    // Initialize member variables
    //

    // Set initial zoom/scroll direction
    m_ChartViewer->setScrollDirection(Chart::DirectionHorizontalVertical);
    m_ChartViewer->setZoomDirection(Chart::DirectionHorizontalVertical);

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

    // Enable mouse wheel zooming by setting the zoom ratio to 1.1 per wheel event
    m_ChartViewer->setMouseWheelZoomRatio(1.1);

    // Load the data
    loadData();

    // Can update chart now
    m_ChartViewer->updateViewPort(true, true);

    // Configure the CViewPortControl to use transparent black for region outside the viewport,
    // that is, to darken the outside region.
    m_ViewPortControl->setViewPortExternalColor(0x7f000000);
    m_ViewPortControl->setViewPortBorderColor(0x7fffffff);
    m_ViewPortControl->setSelectionBorderColor(0x7fffffff); 

    // Draw and display the full chart in the QViewPortControl
    drawFullChart(m_ViewPortControl, m_ChartViewer);

    // Bind the QChartViewer to the QViewPortControl
    m_ViewPortControl->setViewer(m_ChartViewer);
}

XYZoomScroll::~XYZoomScroll()
{
    delete m_ChartViewer->getChart();
    delete m_ViewPortControl->getChart();
}

//
// 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
// QChartViewer.updateViewPort.
//
void XYZoomScroll::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 and image map if necessary
    //
    if (m_ChartViewer->needUpdateChart())
        drawChart(m_ChartViewer);
    if (m_ChartViewer->needUpdateImageMap())
        updateImageMap(m_ChartViewer);
}

//
// Update other controls that may be affected by the viewport.
//
void XYZoomScroll::updateControls(QChartViewer *viewer)
{
    //
    // Update the Zoom slider to reflect the current zoom level of the view port
    //
    double smallerSide = viewer->getViewPortWidth() > viewer->getViewPortHeight()
        ? viewer->getViewPortHeight() : viewer->getViewPortWidth();
    m_ZoomBar->setValue((int)(smallerSide * m_ZoomBar->maximum() + 0.5));
}

//
// Load the data
//
void XYZoomScroll::loadData()
{
    //
    // For simplicity, in this demo, we just use hard coded data.
    //
    double X0[] = {10, 15, 6, -12, 14, -8, 13, -3, 16, 12, 10.5, -7, 3, -10, -5, 2, 5};
    double Y0[] = {130, 150, 80, 110, -110, -105, -130, -15, -170, 125,  125, 60, 25, 150,
        150, 15, 120};
    double X1[] = {6, 7, -4, 3.5, 7, 8, -9, -10, -12, 11, 8, -3, -2, 8, 4, -15, 15};
    double Y1[] = {65, -40, -40, 45, -70, -80, 80, 10, -100, 105, 60, 50, 20, 170, -25,
        50, 75};
    double X2[] = {-10, -12, 11, 8, 6, 12, -4, 3.5, 7, 8, -9, 3, -13, 16, -7.5, -10, -15};
    double Y2[] = {65, -80, -40, 45, -70, -80, 80, 90, -100, 105, 60, -75, -150, -40, 120,
        -50, -30};

    dataX0.assign(X0, X0 + sizeof(X0) / sizeof(*X0));
    dataY0.assign(Y0, Y0 + sizeof(Y0) / sizeof(*Y0));
    dataX1.assign(X1, X1 + sizeof(X1) / sizeof(*X1));
    dataY1.assign(Y1, Y1 + sizeof(Y1) / sizeof(*Y1));
    dataX2.assign(X2, X2 + sizeof(X2) / sizeof(*X2));
    dataY2.assign(Y2, Y2 + sizeof(Y2) / sizeof(*Y2));
}

//
// Draw the chart and display it in the given viewer
//
void XYZoomScroll::drawChart(QChartViewer *viewer)
{
    // Create an XYChart object 500 x 480 pixels in size, with the same background color
    // as the container
    QColor bgColor = palette().color(backgroundRole()).rgb();
    XYChart *c = new XYChart(500, 480, (bgColor.red() << 16) + (bgColor.green() << 8) + bgColor.blue());

    // Set the plotarea at (50, 40) and of size 400 x 400 pixels. Use light grey (c0c0c0)
    // horizontal and vertical grid lines. Set 4 quadrant coloring, where the colors of 
    // the quadrants alternate between lighter and deeper grey (dddddd/eeeeee). 
    c->setPlotArea(50, 40, 400, 400, -1, -1, -1, 0xc0c0c0, 0xc0c0c0
        )->set4QBgColor(0xdddddd, 0xeeeeee, 0xdddddd, 0xeeeeee, 0x000000);

    // Enable clipping mode to clip the part of the data that is outside the plot area.
    c->setClipping();

    // Set 4 quadrant mode, with both x and y axes symetrical around the origin
    c->setAxisAtOrigin(Chart::XYAxisAtOrigin, Chart::XAxisSymmetric + Chart::YAxisSymmetric);

    // Add a legend box at (450, 40) (top right corner of the chart) with vertical layout
    // and 8 pts Arial Bold font. Set the background color to semi-transparent grey.
    LegendBox *legendBox = c->addLegend(450, 40, true, "arialbd.ttf", 8);
    legendBox->setAlignment(Chart::TopRight);
    legendBox->setBackground(0x40dddddd);

    // Add a titles to axes
    c->xAxis()->setTitle("Alpha Index");
    c->yAxis()->setTitle("Beta Index");

    // Set axes width to 2 pixels
    c->xAxis()->setWidth(2);
    c->yAxis()->setWidth(2);

    // The default ChartDirector settings has a denser y-axis grid spacing and less-dense
    // x-axis grid spacing. In this demo, we want the tick spacing to be symmetrical.
    // We use around 50 pixels between major ticks and 25 pixels between minor ticks.
    c->xAxis()->setTickDensity(50, 25);
    c->yAxis()->setTickDensity(50, 25);

    //
    // In this example, we represent the data by scatter points. If you want to represent
    // the data by somethings else (lines, bars, areas, floating boxes, etc), just modify
    // the code below to use the layer type of your choice. 
    //

    // Add scatter layer, using 11 pixels red (ff33333) X shape symbols
    c->addScatterLayer(vectorToArray(dataX0), vectorToArray(dataY0), "Group A", 
        Chart::Cross2Shape(), 11, 0xff3333);

    // Add scatter layer, using 11 pixels green (33ff33) circle symbols
    c->addScatterLayer(vectorToArray(dataX1), vectorToArray(dataY1), "Group B", 
        Chart::CircleShape, 11,  0x33ff33);

    // Add scatter layer, using 11 pixels blue (3333ff) triangle symbols
    c->addScatterLayer(vectorToArray(dataX2), vectorToArray(dataY2), "Group C", 
        Chart::TriangleSymbol, 11, 0x3333ff);

    //
    // In this example, we have not explicitly configured the full x and y range. In this case, 
    // the first time syncLinearAxisWithViewPort is called, ChartDirector will auto-scale the axis
    // and assume the resulting range is the full range. In subsequent calls, ChartDirector will 
    // set the axis range based on the view port and the full range.
    //
    viewer->syncLinearAxisWithViewPort("x", c->xAxis());
    viewer->syncLinearAxisWithViewPort("y", c->yAxis());
    
    // 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()) && viewer->isMouseOnPlotArea())
        crossHair(c, viewer->getPlotAreaMouseX(), viewer->getPlotAreaMouseY());

    // Set the chart image to the QChartViewer
    delete viewer->getChart();
    viewer->setChart(c);
}

//
// Draw the full thumbnail chart and display it in the given CViewPortControl
//
void XYZoomScroll::drawFullChart(QViewPortControl *vpc, QChartViewer *viewer)
{
    // Create an XYChart object 110 x 110 pixels in size
    XYChart *c = new XYChart(110, 110);

    // Set the plotarea to cover the entire chart. Disable grid lines by setting their colors
    // to transparent. Set 4 quadrant coloring, where the colors of the quadrants alternate
    // between lighter and deeper grey (dddddd/eeeeee).
    c->setPlotArea(0, 0, c->getWidth() - 1, c->getHeight() - 1, -1, -1, -1, Chart::Transparent,
        Chart::Transparent)->set4QBgColor(0xdddddd, 0xeeeeee, 0xdddddd, 0xeeeeee, 0x000000);

    // Set 4 quadrant mode, with both x and y axes symetrical around the origin
    c->setAxisAtOrigin(Chart::XYAxisAtOrigin, Chart::XAxisSymmetric + Chart::YAxisSymmetric);

    // The x and y axis scales reflect the full range of the view port
    c->xAxis()->setLinearScale(viewer->getValueAtViewPort("x", 0), viewer->getValueAtViewPort(
        "x", 1), Chart::NoValue);
    c->yAxis()->setLinearScale(viewer->getValueAtViewPort("y", 0), viewer->getValueAtViewPort(
        "y", 1), Chart::NoValue);

    // Add scatter layer, using 11 pixels red (ff33333) X shape symbols
    c->addScatterLayer(vectorToArray(dataX0), vectorToArray(dataY0), "", Chart::Cross2Shape(),
        3, 0xff3333, 0xff3333);

    // Add scatter layer, using 11 pixels green (33ff33) circle symbols
    c->addScatterLayer(vectorToArray(dataX1), vectorToArray(dataY1), "", Chart::CircleShape,
        3, 0x33ff33, 0x33ff33);

    // Add scatter layer, using 11 pixels blue (3333ff) triangle symbols
    c->addScatterLayer(vectorToArray(dataX2), vectorToArray(dataY2), "", Chart::TriangleSymbol,
        3, 0x3333ff, 0x3333ff);

    // Set the chart image to the WinChartViewer
    vpc->setChart(c);
}

//
// Update the image map
//
void XYZoomScroll::updateImageMap(QChartViewer *viewer)
{
    if (0 == viewer->getImageMapHandler())
    {
        // no existing image map - creates a new one
        viewer->setImageMap(viewer->getChart()->getHTMLImageMap("clickable", "",
            "title='[{dataSetName}] Alpha = {x}, Beta = {value}'"));
    }
}

//
// User clicks on the QChartViewer
//
void XYZoomScroll::onClickChart(QMouseEvent *)
{
    ImageMapHandler *handler = m_ChartViewer->getImageMapHandler();
    if (0 != handler)
    {
        // Query the ImageMapHandler to see if the mouse is on a clickable hot spot. We
        // consider the hot spot as clickable if its href ("path") parameter is not empty.
        const char *path = handler->getValue("path");
        if ((0 != path) && (0 != *path))
        {
            // In this sample code, we just show all hot spot parameters.
            HotSpotDialog hs;
            hs.setData(handler);
            hs.exec();
        }
    }
}

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

//
// The Save button is pressed
//
void XYZoomScroll::onSave(bool)
{
    QString fileName = QFileDialog::getSaveFileName(this, "Save", "chartdirector_demo",
        "PNG (*.png);;JPG (*.jpg);;GIF (*.gif);;BMP (*.bmp);;SVG (*.svg);;PDF (*.pdf)");

    if (!fileName.isEmpty())
    {
        // Save the chart
        BaseChart *c = m_ChartViewer->getChart();
        if (0 != c)
            c->makeChart(fileName.toUtf8().constData());
    }
}

//
// User moves the Zoom slider control
//
void XYZoomScroll::onZoomBarChanged(int value)
{
    if (!m_ChartViewer->isInViewPortChangedEvent())
    {
        // Remember the center point
        double centerX = m_ChartViewer->getViewPortLeft() +
            m_ChartViewer->getViewPortWidth() / 2;
        double centerY = m_ChartViewer->getViewPortTop() +
            m_ChartViewer->getViewPortHeight() / 2;

        // Aspect ratio and zoom factor
        double aspectRatio = m_ChartViewer->getViewPortWidth() /
            m_ChartViewer->getViewPortHeight();
        double zoomTo = ((double)value) / m_ZoomBar->maximum();

        // Zoom by adjusting ViewPortWidth and ViewPortHeight while maintaining the aspect ratio
        m_ChartViewer->setViewPortWidth(zoomTo * ((aspectRatio < 1) ? 1 : aspectRatio));
        m_ChartViewer->setViewPortHeight(zoomTo * ((aspectRatio > 1) ? 1 : (1 / aspectRatio)));

        // Adjust ViewPortLeft and ViewPortTop to keep center point unchanged
        m_ChartViewer->setViewPortLeft(centerX - m_ChartViewer->getViewPortWidth() / 2);
        m_ChartViewer->setViewPortTop(centerY - m_ChartViewer->getViewPortHeight() / 2);

        // Update the chart image only, but no need to update the image map.
        m_ChartViewer->updateViewPort(true, false);
    }
}

//
// Draw track cursor when mouse is moving over plotarea, and update image map if necessary
//
void XYZoomScroll::onMouseMovePlotArea(QMouseEvent *)
{
    // Draw crosshair track cursor
    crossHair((XYChart *)m_ChartViewer->getChart(), m_ChartViewer->getPlotAreaMouseX(),
        m_ChartViewer->getPlotAreaMouseY());
    m_ChartViewer->updateDisplay();

    // Hide the track cursor when the mouse leaves the plot area
    m_ChartViewer->removeDynamicLayer("mouseLeavePlotArea");

    // Update image map if necessary. If the mouse is still dragging, the chart is still 
    // updating and not confirmed, so there is no need to set up the image map.
    if (!m_ChartViewer->isMouseDragging())
        updateImageMap(m_ChartViewer);
}

//
// Draw cross hair cursor with axis labels
//
void XYZoomScroll::crossHair(XYChart *c, int mouseX, int mouseY)
{
    // 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();

    // Draw a vertical line and a horizontal line as the cross hair
    d->vline(plotArea->getTopY(), plotArea->getBottomY(), mouseX, d->dashLineColor(0x000000, 0x0101));
    d->hline(plotArea->getLeftX(), plotArea->getRightX(), mouseY, d->dashLineColor(0x000000, 0x0101));

    // Draw y-axis label
    ostringstream ylabel;
    ylabel << "<*block,bgColor=FFFFDD,margin=3,edgeColor=000000*>" << c->formatValue(c->getYValue(
        mouseY, c->yAxis()), "{value|P4}") << "<*/*>";
    TTFText *t = d->text(ylabel.str().c_str(), "arialbd.ttf", 8);
    t->draw(plotArea->getLeftX() - 5, mouseY, 0x000000, Chart::Right);
    t->destroy();

    // Draw x-axis label
    ostringstream xlabel;
    xlabel << "<*block,bgColor=FFFFDD,margin=3,edgeColor=000000*>" << c->formatValue(c->getXValue(
        mouseX), "{value|P4}") << "<*/*>";
    t = d->text(xlabel.str().c_str(), "arialbd.ttf", 8);
    t->draw(mouseX, plotArea->getBottomY() + 5, 0x000000, Chart::Top);
    t->destroy();
}

//
// Convert std::vector to a DoubleArray
//
DoubleArray XYZoomScroll::vectorToArray(std::vector<double> &v)
{
    return (v.size() == 0) ? DoubleArray() : DoubleArray(&(v[0]), v.size());
}