Track Box with Floating Legend (MFC)

NOTE: This section describes Track Box with Floating Legend for MFC only. For Qt, please refer to Track Box with Floating Legend (Qt).

This sample program demonstrates a track cursor programmed with the following features:

A box that horizontally centers around the x data value nearest to the mouse cursor.
A floating legend box that moves with the mouse cursor, displaying the data values at the x data value nearest to the mouse cursor.

The code first draws the chart. Then in the CVN_MouseMovePlotArea message handler, the track cursor is drawn to reflect the mouse position. The track cursor is configured to automatically hide itself when the mouse leaves the plot area.

The trackBoxLegend method is the routine that draws the track cursor. Its key elements are:

To draw dynamic contents on the chart, the code obtains the DrawArea object for drawing on the dynamic layer of the chart using BaseChart.initDynamicLayer.
The nearest x data value is obtained using XYChart.getNearestXValue.
The code draws a rectangle that horizontally spans from (x - 0.5) to (x + 0.5) with DrawArea.rect. The +/- 0.5 offset is the suitable value to use for a label based x-axis (that is, for axis set up with Axis.setLabels or Axis.setLabels2). For this type of axis, the label distance is assumed to be 1 x-axis unit irrespective of what are the labels, so an offset of 0.5 refers to the middle position between two labels.
The code then iterates through all data sets in all layers to find all the data points at the nearest x data value. For each of these points, it formats a legend entry for the point, which consists of the data set icon (obtained using DataSet.getLegendIcon), data set name (obtained using DataSet.getDataName), and the data value (obtained using DataSet.getValue).
Finally, the code combines all the legend entries into a legend box and draws it near the mouse cursor using DrawArea.text.

[MFC version] mfcdemo/TrackBoxDlg.cpp

// TrackBoxDlg.cpp : implementation file
//

#include "stdafx.h"
#include "resource.h"
#include "TrackBoxDlg.h"
#include "chartdir.h"
#include <vector>
#include <sstream>
#include <algorithm>

#ifdef _DEBUG
#define new DEBUG_NEW
#endif

//
// Constructor
//
CTrackBoxDlg::CTrackBoxDlg(CWnd* pParent /*=NULL*/)
    : CDialogEx(IDD_TRACKCURSOR_DEMO, pParent)
{
    SetBackgroundColor(RGB(255, 255, 255));
}

//
// Destructor
//
CTrackBoxDlg::~CTrackBoxDlg()
{
    delete m_ChartViewer.getChart();
}

void CTrackBoxDlg::DoDataExchange(CDataExchange* pDX)
{
    CDialogEx::DoDataExchange(pDX);
    DDX_Control(pDX, IDC_ChartViewer, m_ChartViewer);
}

BEGIN_MESSAGE_MAP(CTrackBoxDlg, CDialogEx)
    ON_CONTROL(CVN_MouseMovePlotArea, IDC_ChartViewer, OnMouseMovePlotArea)
END_MESSAGE_MAP()


//
// Initialization
//
BOOL CTrackBoxDlg::OnInitDialog()
{
    CDialogEx::OnInitDialog();

    SetWindowText(_T("Track Box with Floating Legend"));

    // Draw the chart
    drawChart(&m_ChartViewer);

    // Resize the window to fit the chart size
    CRect winSize;
    m_ChartViewer.GetWindowRect(winSize);
    m_ChartViewer.MoveWindow(5, 5, winSize.Width(), winSize.Height());
    CalcWindowRect(&winSize, CWnd::adjustBorder);
    SetWindowPos(&wndTop, 0, 0, winSize.Width() + 10, winSize.Height() + 10, SWP_NOMOVE);
 
    return TRUE;
}

//
// Draw track cursor when mouse is moving over plotarea
//
void CTrackBoxDlg::OnMouseMovePlotArea()
{
    trackBoxLegend((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(CVN_MouseLeavePlotArea);
}

//
// Draw the chart and display it in the given viewer
//
void CTrackBoxDlg::drawChart(CChartViewer *viewer)
{
    // The data for the bar chart
    double data0[] = {100, 125, 245, 147, 67};
    double data1[] = {85, 156, 179, 211, 123};
    double data2[] = {97, 87, 56, 267, 157};
    const char *labels[] = {"Mon", "Tue", "Wed", "Thur", "Fri"};
    int noOfPoints = (int)(sizeof(data0)/sizeof(*data0));

    // Create a XYChart object of size 540 x 375 pixels
    XYChart *c = new XYChart(540, 375);

    // Add a title to the chart using 18 pts Times Bold Italic font
    c->addTitle("Average Weekly Network Load", "Times New Roman Bold Italic", 18);

    // Set the plotarea at (50, 55) and of 440 x 280 pixels in size. Use a vertical gradient color
    // from light blue (f9f9ff) to blue (6666ff) as background. Set border and grid lines to white
    // (ffffff).
    c->setPlotArea(50, 55, 440, 280, c->linearGradientColor(0, 55, 0, 335, 0xf9f9ff, 0x6666ff), -1,
        0xffffff, 0xffffff);

    // Add a legend box at (50, 28) using horizontal layout. Use 10pts Arial Bold as font, with
    // transparent background.
    c->addLegend(50, 28, false, "Arial Bold", 10)->setBackground(Chart::Transparent);

    // Set the x axis labels
    c->xAxis()->setLabels(StringArray(labels, noOfPoints));

    // Draw the ticks between label positions (instead of at label positions)
    c->xAxis()->setTickOffset(0.5);

    // Set axis label style to 8pts Arial Bold
    c->xAxis()->setLabelStyle("Arial Bold", 8);
    c->yAxis()->setLabelStyle("Arial Bold", 8);

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

    // Add axis title
    c->yAxis()->setTitle("Throughput (MBytes Per Hour)");

    // Add a multi-bar layer with 3 data sets
    BarLayer *layer = c->addBarLayer(Chart::Side);
    layer->addDataSet(DoubleArray(data0, noOfPoints), 0xff0000, "Server #1");
    layer->addDataSet(DoubleArray(data1, noOfPoints), 0x00ff00, "Server #2");
    layer->addDataSet(DoubleArray(data2, noOfPoints), 0xff8800, "Server #3");

    // Set bar border to transparent. Use glass lighting effect with light direction from left.
    layer->setBorderColor(Chart::Transparent, Chart::glassEffect(Chart::NormalGlare, Chart::Left));

    // Configure the bars within a group to touch each others (no gap)
    layer->setBarGap(0.2, Chart::TouchBar);

    // Assign the chart to the WinChartViewer
    viewer->setChart(c);
}

//
// Draw the track box with legend
//
void CTrackBoxDlg::trackBoxLegend(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();

    // Get the data x-value that is nearest to the mouse
    double xValue = c->getNearestXValue(mouseX);

    // Compute the position of the box. This example assumes a label based x-axis, in which the
    // labeling spacing is one x-axis unit. So the left and right sides of the box is 0.5 unit from
    // the central x-value.
    int boxLeft = c->getXCoor(xValue - 0.5);
    int boxRight = c->getXCoor(xValue + 0.5);
    int boxTop = plotArea->getTopY();
    int boxBottom = plotArea->getBottomY();

    // Draw the track box
    d->rect(boxLeft, boxTop, boxRight, boxBottom, 0x000000, Chart::Transparent);

    // Container to hold the legend entries
    std::vector<std::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);

            // Build the legend entry, consist of the legend icon, the name and the data value.
            double dataValue = dataSet->getValue(xIndex);
            if ((dataValue != Chart::NoValue) && (dataSet->getDataColor() != Chart::Transparent)) {
                std::ostringstream legendEntry;
                legendEntry << dataSet->getLegendIcon() << " " << dataSet->getDataName() << ": "
                    << c->formatValue(dataValue, "{value|P4}");
                legendEntries.push_back(legendEntry.str());
            }
        }
    }

    // Create the legend by joining the legend entries
    if (legendEntries.size() > 0) {
        std::ostringstream legend;
        legend << "<*block,bgColor=FFFFCC,edgeColor=000000,margin=5*><*font,underline=1*>" <<
            c->xAxis()->getFormattedLabel(xValue) << "<*/font*>";
        for (int i = ((int)legendEntries.size()) - 1; i >= 0; --i)
            legend << "<*br*>" << legendEntries[i];
        legend << "<*/*>";

        // Display the legend at the bottom-right side of the mouse cursor, and make sure the legend
        // will not go outside the chart image.
        TTFText* t = d->text(legend.str().c_str(), "Arial Bold", 8);
        t->draw((std::min)(mouseX + 12, c->getWidth() - t->getWidth()), (std::min)(mouseY + 18, 
            c->getHeight() - t->getHeight()), 0x000000, Chart::TopLeft);
        t->destroy();
    }
}