Helpers: add get_cylinder_used_gas_string()

get_cylinder_used_gas_string() retrieves used gas per cylinder
with optional units display.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/qt-gui.cpp b/qt-gui.cpp
index 41a6617e1..64a125dcb 100644
--- a/qt-gui.cpp
+++ b/qt-gui.cpp
@@ -233,6 +233,37 @@ QString get_weight_unit()
 		return "lbs";
 }
 
+/* these methods retrieve used gas per cylinder */
+static unsigned start_pressure(cylinder_t *cyl)
+{
+	return cyl->start.mbar ? : cyl->sample_start.mbar;
+}
+
+static unsigned end_pressure(cylinder_t *cyl)
+{
+	return cyl->end.mbar ? : cyl->sample_end.mbar;
+}
+
+QString get_cylinder_used_gas_string(cylinder_t *cyl, bool showunit)
+{
+	int decimals;
+	const char *unit;
+	double gas_usage;
+	/* Get the cylinder gas use in mbar */
+	gas_usage = start_pressure(cyl) - end_pressure(cyl);
+	/* Can we turn it into a volume? */
+	if (cyl->type.size.mliter) {
+		gas_usage = bar_to_atm(gas_usage / 1000);
+		gas_usage *= cyl->type.size.mliter;
+		gas_usage = get_volume_units(gas_usage, &decimals, &unit);
+	} else {
+		gas_usage = get_pressure_units(gas_usage, &unit);
+		decimals = 0;
+	}
+	// tr("%.*f %s"
+	return QString("%1 %2").arg(gas_usage, 0, 'f', decimals).arg(showunit ? unit : "");
+}
+
 QString get_temperature_string(temperature_t temp, bool showunit)
 {
 	if (prefs.units.temperature == units::CELSIUS) {