Grapher Plugin

This example graphs data from a simple text file. It demonstrates the use of the QNPInstance::writeReady() and QNPInstance::write() functions.

To build the example, you must first build the Qt Netscape Plugin Extension library. Then type make in extensions/nsplugin/examples/grapher/ and copy the resulting grapher.so or npgrapher.dll to the Plugins directory of your WWW browser.

The text file it accepts as input has a title line, then a sequence of lines with an number then a string. The plugin displays a pie chart of the numbers, each segment labelled by the associated string. The user can select a bar chart view of the same data by selecting from the menu that appears when they point at the plugin.

The HTML tag used to embed the graph is:

  <EMBED
    SRC=graph.g1n
    ALIGN=LEFT
    WIDTH=49% HEIGHT=300
    graphstyle=pie fontfamily=times
    fontsize=18>

// Include Qt Netscape Plugin classes.
#include "qnp.h"

// Include other Qt classes.
#include <qpainter.h>
#include <qtextstream.h>
#include <qbuffer.h>
#include <qpixmap.h>
#include <qmenubar.h>
#include <qpushbutton.h>
#include <qlist.h>
#include <qmessagebox.h>

// Include some C library functions.
#include <math.h>
#include <stdlib.h>

#ifndef M_PI // Some math.h don't include this.
#define M_PI 3.14159265358979323846264338327950288
#endif

//
// GraphModel is a simple abstract class that describes
// a table of numeric and text data.
//

class GraphModel {
public:
    enum ColType { Numeric, Label };

    union Datum {
        double dbl;
        QString* str;
    };

    virtual QList<Datum>& graphData()=0;
    virtual ColType colType(int col) const=0;
    virtual int nCols() const=0;
};

//
// Graph is a widget subclass that displays a GraphModel.
// Since the widget is a QNPWidget, it can be used as a plugin window,
// returned by Grapher::newWindow() below.
//

class Graph : public QNPWidget {
    Q_OBJECT
public:
    // Constructs a Graph to display a GraphModel
    //
    Graph(GraphModel&);
    ~Graph();

    // Two styles are available - Pie and Bar graph
    //
    enum Style { Pie, Bar };
    static const char* styleName[];
    void setStyle(Style);
    void setStyle(const char*);

    // Timer event processing rotates the pie graph
    //
    void timerEvent(QTimerEvent*);

    // These functions are provided by QNPWidget - we override
    // them to hide and show the plugin menubar.
    //
    void enterInstance();
    void leaveInstance();

    // Paint the graph...
    //
    void paintEvent(QPaintEvent*);
    //
    // ... as either a "Loading" message, a Bar graph, a Pie graph,
    // or an error message.
    //
    void paintWait(QPaintEvent*);
    void paintBar(QPaintEvent*);
    void paintPie(QPaintEvent*);
    void paintError(const char*);

signals:
    // Signals emitted when the Help menus are selected.
    void aboutPlugin();
    void aboutData();

private:
    GraphModel& model;
    QMenuBar *menubar;
    Style style;
    QPopupMenu* stylemenu;
    int pieRotationTimer;
    int pieRotation;
    QPixmap pm;

private slots:
    void setStyleFromMenu(int id);
};

Graph::Graph( GraphModel& mdl ) :
    model(mdl),
    style(Bar),
    pieRotationTimer(0),
    pieRotation(0)
{
    // Create a menubar for the widget
    //
    menubar = new QMenuBar( this );
    stylemenu = new QPopupMenu;
    stylemenu->setCheckable(TRUE);
    for ( Style s = Pie; styleName[s]; s = Style(s+1)) {
        stylemenu->insertItem(styleName[s], s+100);
    }
    connect(stylemenu, SIGNAL(activated(int)),
        this, SLOT(setStyleFromMenu(int)));
    setStyle(Pie);

    menubar->insertItem("Style", stylemenu);
    menubar->insertSeparator();

    QPopupMenu* help = new QPopupMenu;
    help->insertItem( "About plugin...", this, SIGNAL(aboutPlugin()) );
    help->insertItem( "About data...", this, SIGNAL(aboutData()) );
    menubar->insertItem("Help", help);
}

Graph::~Graph()
{
}

void Graph::setStyle(Style s)
{
    if (style != s) {
        if (pieRotationTimer)
            killTimer(pieRotationTimer);
        stylemenu->setItemChecked(100+style, FALSE);
        style = s;
        if ( style == Pie )
            pieRotationTimer = startTimer( 80 );
        else
            pieRotationTimer = 0;
        stylemenu->setItemChecked(100+style, TRUE);
        update();
    }
}

void Graph::timerEvent(QTimerEvent*)
{
    pieRotation = ( pieRotation + 6 ) % 360; repaint(FALSE);
}

void Graph::setStyle(const char* stext)
{
    for ( Style s = Pie; styleName[s]; s = Style(s+1) ) {
        if ( stricmp(stext,styleName[s])==0 ) {
            setStyle(s);
            return;
        }
    }
}

void Graph::enterInstance()
{
    menubar->show();
}

void Graph::leaveInstance()
{
    menubar->hide();
}

void Graph::paintError(const char* e)
{
    QPainter p(this);
    int w = width();
    p.drawText(w/8, 0, w-w/4, height(), AlignCenter|WordBreak, e);
}

void Graph::paintBar(QPaintEvent* event)
{
    if ( model.colType(0) != GraphModel::Numeric ) {
        paintError("First column not numeric, cannot draw bar graph\n");
        return;
    }

    QList<GraphModel::Datum>& data = model.graphData();

    double max = 0.0;

    for (GraphModel::Datum* rowdata = data.first();
        rowdata; rowdata = data.next())
    {
        if (rowdata[0].dbl > max) max = rowdata[0].dbl;
    }

    const uint w = width();
    const uint h = height();

    QPainter p(this);

    p.setClipRect(event->rect());

    if ( w > data.count() ) {
        // More pixels than data
        int x = 0;
        int i = 0;
        QFontMetrics fm=fontMetrics();
        int fh = fm.height();

        for (GraphModel::Datum* rowdata = data.first();
            rowdata; rowdata = data.next())
        {
            QColor c;
            c.setHsv( (i * 255)/data.count(), 255, 255 );// rainbow effect
            p.setBrush(c);
            int bw = (w-w/4-x)/(data.count()-i);
            int bh = int((h-h/4-1)*rowdata[0].dbl/max);
            p.drawRect( w/8+x, h-h/8-1-bh, bw, bh );
            if (model.colType(1) == GraphModel::Label) {
                p.drawText(w/8+x, h-h/8, bw, fh+h/8,
                    WordBreak|AlignTop|AlignHCenter,
                    *rowdata[1].str);
            }
            i++;
            x+=bw;
        }
    } else {
        // More data than pixels
        int x = 0;
        int i = 0;
        double av = 0.0;
        int n = 0;
        for (GraphModel::Datum* rowdata = data.first(); rowdata;
            rowdata = data.next())
        {
            int bx = i*w/data.count();

            if (bx > x) {
                QColor c;
                c.setHsv( (x * 255)/w, 255, 255 );// rainbow effect
                p.setPen(c);
                int bh = int(h*av/n/max);

                p.drawLine(x,h-1,x,h-bh);

                av = 0.0;
                n = 0;
                x = bx;
            }

            av += rowdata[0].dbl;
            n++;

            i++;
        }
    }
}

void Graph::paintPie(QPaintEvent* event)
{
    if ( model.colType(0) != GraphModel::Numeric ) {
        paintError("First column not numeric, cannot draw pie graph\n");
        return;
    }

    QList<GraphModel::Datum>& data = model.graphData();

    double total = 0.0;

    GraphModel::Datum* rowdata;

    for (rowdata = data.first();
        rowdata; rowdata = data.next())
    {
        total += rowdata[0].dbl;
    }

    // Only use first column for pie chart
    if ( !total ) return;

    int apos = (pieRotation-90)*16;

    const int w = width();
    const int h = height();

    const int xd = w - w/5;
    const int yd = h - h/5;

    pm.resize(width(),height());
    pm.fill(backgroundColor());
    QPainter p(&pm);
    p.setFont(font());

    p.setClipRect(event->rect());

    int i = 0;

    for (rowdata = data.first();
        rowdata; rowdata = data.next())
    {
        QColor c;

        c.setHsv( ( i * 255)/data.count(), 255, 255 );// rainbow effect
        p.setBrush( c );                        // solid fill with color c

        int a = int(( rowdata[0].dbl * 360.0 ) / total * 16.0 + 0.5);
        p.drawPie( w/10, h/10, xd, yd, -apos, -a );
        apos += a;
        i++;
    }

    if (model.colType(1) == GraphModel::Label) {
        double apos = (pieRotation-90)*M_PI/180;

        for (rowdata = data.first();
            rowdata; rowdata = data.next())
        {
            double a = rowdata[0].dbl * 360 / total * M_PI / 180;
            int x = int(cos(apos+a/2)*w*5/16 + w/2 + 0.5);
            int y = int(sin(apos+a/2)*h*5/16 + h/2 + 0.5);
            p.drawText(x-w/8, y-h/8, w/4, h/4,
                WordBreak|AlignCenter,
                *rowdata[1].str);
            apos += a;
        }
    }

    QPainter p2(this);
    p2.setClipRect(event->rect());
    p2.drawPixmap(0,0,pm);
}

void Graph::paintWait(QPaintEvent*)
{
    QPainter p(this);
    p.drawText(rect(), AlignCenter, "Loading...");
}

void Graph::paintEvent(QPaintEvent* event)
{
    if (!model.nCols()) {
        paintWait(event);
    } else {
        switch (style) {
          case Pie:
            paintPie(event);
            break;
          case Bar:
            paintBar(event);
            break;
        }
    }
}

void Graph::setStyleFromMenu(int id)
{
    setStyle(Style(id-100));
}

const char* Graph::styleName[] = { "Pie", "Bar", 0 };

//
// Grapher is a subclass of QNPInstance, and so it can be returned
// by GrapherPlugin::newInstance().  A QNPInstance represents the
// plugin, distinctly from the plugin window.
//
// Grapher is also a GraphModel, because it loads graph data from
// the net.  When Grapher creates a windoiw in newWindow(), it creates
// a Graph widget to display the GraphModel that is the Grapher itself.
//

class Grapher : public QNPInstance, GraphModel {
    Q_OBJECT
public:
    // Create a Grapher - all Grapher plugins are created
    // by one GrapherPlugin object.
    //
    Grapher();
    ~Grapher();

    // We override this QNPInstance function to create our
    // own subclass of QNPWidget, a Graph widget.
    //
    QNPWidget* newWindow();

    // We override this QNPInstance function to process the
    // incoming graph data.
    //
    int write(QNPStream* /*str*/, int /*offset*/, int len, void* buffer);

private:
    // Grapher is a GraphModel, so it implements the pure virtual
    // functions of that class.
    //
    QList<Datum>& graphData();
    ColType colType(int col) const;
    int nCols() const;

    void consumeLine();
    QList<Datum> data;
    QBuffer line;
    bool firstline;
    int ncols;
    ColType *coltype;

private slots:
    // Slots that are connected to the Graph menu items.
    //
    void aboutPlugin();
    void aboutData();
};

Grapher::Grapher()
{
    data.setAutoDelete(TRUE);
    firstline = TRUE;
    ncols = 0;
    line.open(IO_WriteOnly|IO_Truncate);
}

Grapher::~Grapher()
{
}

QList<GraphModel::Datum>& ">Grapher::graphData()
{
    return data;
}

GraphModel::ColType Grapher::colType(int col) const
{
    return coltype[col];
}

int Grapher::nCols() const
{
    return ncols;
}

QNPWidget* Grapher::newWindow()
{
    // Create a Graph - our subclass of QNPWidget.
    Graph *graph = new Graph(*this);

    // Look at the arguments from the EMBED tag.
    //   GRAPHSTYLE chooses pie or bar
    //   FONTFAMILY and FONTSIZE choose the font
    //
    const char* style = arg("GRAPHSTYLE");
    if ( style ) graph->setStyle(style);

    const char* fontfamily = arg("FONTFAMILY");
    const char* fontsize = arg("FONTSIZE");
    int ptsize = fontsize ? atoi(fontsize) : graph->font().pointSize();
    if (fontfamily) graph->setFont(QFont(fontfamily, ptsize));

    connect(graph, SIGNAL(aboutPlugin()), this, SLOT(aboutPlugin()));
    connect(graph, SIGNAL(aboutData()), this, SLOT(aboutData()));

    return graph;
}

void Grapher::consumeLine()
{
    line.close();
    line.open(IO_ReadOnly);

    QTextStream ts( &line );

    if (firstline) {
        firstline = FALSE;
        ncols=0;
        QList<ColType> typelist;
        typelist.setAutoDelete(TRUE);
        do {
            QString typestr;
            ts >> typestr >> ws;
            ColType* t = 0;
            if ( typestr == "num" ) {
                t = new ColType(Numeric);
            } else if ( typestr == "label" ) {
                t = new ColType(Label);
            }
            if (t) typelist.append(t);
        } while (!ts.eof());
        coltype = new ColType[ncols];
        for (ColType* t = typelist.first(); t; t = typelist.next()) {
            coltype[ncols++] = *t;
        }
    } else {
        int col=0;
        Datum *rowdata = new Datum[ncols];
        while ( col < ncols && !ts.eof() ) {
            switch (coltype[col]) {
              case Numeric: {
                double value;
                ts >> value >> ws;
                rowdata[col].dbl = value;
                break;
              }
              case Label: {
                QString* value = new QString;
                ts >> *value >> ws;
                rowdata[col].str = value;
                break;
              }
            }
            col++;
        }

        data.append(rowdata);
    }

    line.close();
    line.open(IO_WriteOnly|IO_Truncate);
}

int Grapher::write(QNPStream* /*str*/, int /*offset*/, int len, void* buffer)
{
    // The browser calls this function when data is available on one
    // of the streams the plugin has requested.  Since we are only
    // processing one stream - the URL in the SRC argument of the EMBED
    // tag, we assume the QNPStream is that one.  Also, since we do not
    // override QNPInstance::writeReady(), we must accepts ALL the data
    // that is sent to this function.
    //
    char* txt = (char*)buffer;
    for (int i=0; i<len; i++) {
        char ch = txt[i];
        switch ( ch ) {
          case '\n':
            consumeLine();
            break;
          case '\r': // ignore;
            break;
          default:
            line.putch(ch);
        }
    }

    if ( widget() ) {
        widget()->update();
    }

    return len;
}

void Grapher::aboutPlugin()
{
    getURL( "http://www.troll.no/nsplugin/", "_blank" );
}

void Grapher::aboutData()
{
    const char* page = arg("DATAPAGE");
    if (page)
        getURL( page, "_blank" );
    else
        QMessageBox::message("Help", "No help for this data");
}

//
// GrapherPlugin is the start of everything.  It is a QNPlugin subclass,
// and it is responsible for describing the plugin to the browser, and
// creating instances of the plugin when it appears in web page.
//

class GrapherPlugin : public QNPlugin {
public:
    GrapherPlugin()
    {
    }

    QNPInstance* newInstance()
    {
        // Make a new Grapher, our subclass of QNPInstance.
        return new Grapher;
    }

    const char* getMIMEDescription() const
    {
        // Describe the MIME types which this plugin can
        // process.  Just the concocted "application/x-graphable"
        // type, with the "g1n" filename extension.
        //
        return "application/x-graphable:g1n:Graphable ASCII numeric data";
    }

    const char * getPluginNameString() const
    {
        // The name of the plugin.  This is the title string used in
        // the "About Plugins" page of the browser.
        //
        return "Qt-based Graph Plugin";
    }

    const char * getPluginDescriptionString() const
    {
        // A longer description of the plugin.
        //
        return "A Qt-based LiveConnected plug-in that graphs numeric data";
    }

};

//
// Finally, we provide the implementation of QNPlugin::create(), to
// provide our subclass of QNPlugin.
//

QNPlugin* QNPlugin::create()
{
    return new GrapherPlugin;
}

#include "grapher.moc"