Added heart rate graph

Improved graphs loading performance
Fixed various corner case behaviour bugs

src/heartrategraph.cpp

@@ -0,0 +1,87 @@
+#include "gpx.h"
+#include "heartrategraph.h"
+
+
+HeartRateGraph::HeartRateGraph(QWidget *parent) : GraphView(parent)
+{
+	_max = 0;
+
+	setXLabel(tr("Distance"));
+	setYLabel(tr("Heart rate"));
+	setXUnits(tr("km"));
+	setYUnits(tr("1/min"));
+	setXScale(M2KM);
+	setPrecision(0);
+}
+
+void HeartRateGraph::addInfo()
+{
+	GraphView::addInfo(tr("Average"), QString::number(avg() * _yScale, 'f', 0)
+	  + UNIT_SPACE + _yUnits);
+	GraphView::addInfo(tr("Maximum"), QString::number(_max * _yScale,  'f', 0)
+	  + UNIT_SPACE + _yUnits);
+}
+
+void HeartRateGraph::loadGPX(const GPX &gpx)
+{
+	for (int i = 0; i < gpx.trackCount(); i++) {
+		QVector<QPointF> data;
+		qreal max = 0, sum = 0, w = 0;
+
+		gpx.track(i).heartRateGraph(data);
+		if (data.count() < 2) {
+			skipColor();
+			continue;
+		}
+
+		for (int j = 1; j < data.size(); j++) {
+			sum += data.at(j).y() * (data.at(j).x() - data.at(j-1).x());
+			w += data.at(j).x() - data.at(j-1).x();
+		}
+		_avg.append(QPointF(gpx.track(i).distance(), sum/w));
+
+		for (int j = 0; j < data.size(); j++)
+			max = qMax(max, data.at(j).y());
+		_max = qMax(_max, max);
+
+		addInfo();
+		loadData(data);
+	}
+}
+
+qreal HeartRateGraph::avg() const
+{
+	qreal sum = 0, w = 0;
+	QList<QPointF>::const_iterator it;
+
+	for (it = _avg.begin(); it != _avg.end(); it++) {
+		sum += it->y() * it->x();
+		w += it->x();
+	}
+
+	return (sum / w);
+}
+
+void HeartRateGraph::clear()
+{
+	_max = 0;
+	_avg.clear();
+
+	GraphView::clear();
+}
+
+void HeartRateGraph::setUnits(enum Units units)
+{
+	if (units == Metric) {
+		setXUnits(tr("km"));
+		setXScale(M2KM);
+	} else {
+		setXUnits(tr("mi"));
+		setXScale(M2MI);
+	}
+
+	clearInfo();
+	addInfo();
+
+	redraw();
+}