ChartDirector 5.1 (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 and the mouse wheel to control zooming. There is also a "navigation pad" which can be thought as a representation of the view port. You can drag the pad to move the view port around (that is, to perform 2D scrolling). 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.

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 "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);

    // 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)));

    // The container of the draggable navigation window
    m_NavigatePad = new QFrame(frame);
    m_NavigatePad->setGeometry(4, 364, 113, 113);
    m_NavigatePad->setFrameShape(QFrame::Panel);
    m_NavigatePad->setFrameShadow(QFrame::Sunken);

    // The dragging navigation window
    m_NavigateWindow = new QDragRect(m_NavigatePad);
    m_NavigateWindow->setGeometry(24, 28, 61, 53);
    m_NavigateWindow->setAutoFillBackground(true);
    m_NavigateWindow->setPalette(QPalette(QColor(0xc0, 0xc0, 0xff)));
    m_NavigateWindow->setFrameShape(QFrame::Box);
    m_NavigateWindow->setFrameShadow(QFrame::Plain);
    connect(m_NavigateWindow, SIGNAL(mouseDrag(QPoint, QPoint)),
            SLOT(onNavigateWindowDrag(QPoint, QPoint)));

    // 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(mouseWheel(QWheelEvent*)), SLOT(onMouseWheelChart(QWheelEvent*)));
    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();

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

XYZoomScroll::~XYZoomScroll()
{
    delete m_ChartViewer->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);

    // 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 ((!m_ChartViewer->isInMouseMoveEvent()) && m_ChartViewer->isMouseOnPlotArea())
    {
        crossHair((XYChart *)m_ChartViewer->getChart(), m_ChartViewer->getPlotAreaMouseX(),
            m_ChartViewer->getPlotAreaMouseY());
        m_ChartViewer->updateDisplay();
    }
}

//
// Update controls when the view port changed
//
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));

    //
    // Update the navigate window to reflect the current view port position and size. (Note:
    // we allowed for a 2-pixel margin for the frame border in the following computations.)
    //
    int borderWidth = m_NavigatePad->frameWidth();
    int left = (int)(viewer->getViewPortLeft() * (m_NavigatePad->width() - borderWidth * 2) + borderWidth + 0.5);
    int top = (int)(viewer->getViewPortTop() * (m_NavigatePad->height() - borderWidth * 2) + borderWidth + 0.5);
    int width = (int)(viewer->getViewPortWidth() * (m_NavigatePad->width() - borderWidth * 2) + 0.5);
    int height = (int)(viewer->getViewPortHeight() * (m_NavigatePad->height() - borderWidth * 2) + 0.5);
    m_NavigateWindow->setGeometry(left, top, width, height);
}

//
// Draw the chart and display it in the given viewer
//
void XYZoomScroll::drawChart(QChartViewer *viewer)
{
    //
    // For simplicity, in this demo, we just use hard coded data. In a real application,
    // the data probably read from a dynamic source such as a database. (See the
    // ChartDirector documentation on "Using Data Sources with ChartDirector" if you need
    // some sample code on how to read data from database to array variables.)
    //
    double dataX0[] = {10, 15, 6, -12, 14, -8, 13, -3, 16, 12, 10.5, -7, 3, -10, -5, 2, 5};
    double dataY0[] = {130, 150, 80, 110, -110, -105, -130, -15, -170, 125,  125, 60, 25, 150,
        150,15, 120};
    double dataX1[] = {6, 7, -4, 3.5, 7, 8, -9, -10, -12, 11, 8, -3, -2, 8, 4, -15, 15};
    double dataY1[] = {65, -40, -40, 45, -70, -80, 80, 10, -100, 105, 60, 50, 20, 170, -25,
        50, 75};
    double dataX2[] = {-10, -12, 11, 8, 6, 12, -4, 3.5, 7, 8, -9, 3, -13, 16, -7.5, -10, -15};
    double dataY2[] = {65, -80, -40, 45, -70, -80, 80, 90, -100, 105, 60, -75, -150, -40, 120,
        -50, -30};

    // 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(DoubleArray(dataX0, sizeof(dataX0) / sizeof(dataX0[0])),
        DoubleArray(dataY0, sizeof(dataY0) / sizeof(dataY0[0])), "Group A",
        Chart::Cross2Shape(), 11, 0xff3333);

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

    // Add scatter layer, using 11 pixels blue (3333ff) triangle symbols
    c->addScatterLayer(DoubleArray(dataX2, sizeof(dataX2) / sizeof(dataX2[0])),
        DoubleArray(dataY2, sizeof(dataY2) / sizeof(dataY2[0])),
        "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());

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

//
// 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);
    }
}

//
// Scroll the chart when the user drags the navigate window
//
void XYZoomScroll::onNavigateWindowDrag(QPoint fromPoint, QPoint toPoint)
{
    //
    // Get the position of the navigate window inside the navigate pad as a ratio between 0 - 1.
    //
    double viewPortLeft = ((double)m_NavigateWindow->x() + toPoint.x() - fromPoint.x() -
        m_NavigatePad->frameWidth()) / (m_NavigatePad->width() - m_NavigatePad->frameWidth() * 2);
    double viewPortTop = ((double)m_NavigateWindow->y() + toPoint.y() - fromPoint.y() -
        m_NavigatePad->frameWidth()) / (m_NavigatePad->height() - m_NavigatePad->frameWidth() * 2);

    scrollChartTo(viewPortLeft, viewPortTop);
}

//
// Scroll the view port to the given position if necessary
//
void XYZoomScroll::scrollChartTo(double viewPortLeft, double viewPortTop)
{
    //
    // Ensures the view port is within valid range.
    //
    viewPortLeft = max(0.0, min(viewPortLeft, 1 - m_ChartViewer->getViewPortWidth()));
    viewPortTop = max(0.0, min(viewPortTop, 1 - m_ChartViewer->getViewPortHeight()));

    //
    // Update chart only if the view port has actually changed
    //
    if ((viewPortLeft != m_ChartViewer->getViewPortLeft()) ||
        (viewPortTop != m_ChartViewer->getViewPortTop()))
    {
        m_ChartViewer->setViewPortLeft(viewPortLeft);
        m_ChartViewer->setViewPortTop(viewPortTop);

        // Update the chart image only, but no need to update the image map.
        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 XYZoomScroll::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, 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
    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();
}