Add initial support for a visual tracker of gas used

This shows a color-coded bar at the bottom of the graph that corresponds
with the active gas.

Todo:
- text that explicitly states gas on the left edge of the bar
- better vertical positioning of the bar
- ability to turn this on and off

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/profile/tankitem.h

@@ -0,0 +1,34 @@
+#ifndef TANKITEM_H
+#define TANKITEM_H
+
+#include <QGraphicsItem>
+#include <QModelIndex>
+#include "divelineitem.h"
+#include "divecartesianaxis.h"
+#include "dive.h"
+
+class TankItem : public QObject, public QGraphicsRectItem
+{
+	Q_OBJECT
+	Q_INTERFACES(QGraphicsItem)
+
+public:
+	explicit TankItem(QObject *parent = 0);
+	void setHorizontalAxis(DiveCartesianAxis *horizontal);
+	void setData(DivePlotDataModel *model, struct plot_info *plotInfo, struct dive *d);
+
+signals:
+
+public slots:
+	virtual void modelDataChanged(const QModelIndex &topLeft = QModelIndex(), const QModelIndex &bottomRight = QModelIndex());
+
+private:
+	DivePlotDataModel *dataModel;
+	DiveCartesianAxis *hAxis;
+	int hDataColumn;
+	struct dive *dive;
+	struct plot_info *pInfo;
+	QList<QGraphicsRectItem *> rects;
+};
+
+#endif // TANKITEM_H