Add cylinder equipment tooltips with gas volume

This adds tooltips for the equipment tab for each cylinder, showing the
amount of gas used.

When you mouse over the size and working pressure fields, the tooltip will
show the amount of gas used (along with start and end gas volumes). And
when you mouse over the start and end pressures, it will show the start
and end gas volumes, and the Z factor used.

I started doing this because of the gas volume questions in the last day
or two (and a few from a few weeks ago). When even Robert Helling starts
wondering about the effects of compressibility on the SAC calculation, our
numbers are clearly too opaque.

With these tooltips, at least you can see what went into the used gas
calculations, instead of having to add debugging options to print out Z
factors.

[ This patch also adds a "rint()" to get the rounding right in the
  gas_volume() function.  Although rounding to the nearst milliliter
  really doesn't matter, it's the right thing to do after doing FP
  calculations ;^]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/qt-models/cylindermodel.cpp b/qt-models/cylindermodel.cpp
index 4a9b03864..c2c94f765 100644
--- a/qt-models/cylindermodel.cpp
+++ b/qt-models/cylindermodel.cpp
@@ -51,6 +51,58 @@ static QString get_cylinder_string(cylinder_t *cyl)
 	return QString("%1").arg(value, 0, 'f', decimals) + unit;
 }
 
+static QString gas_volume_string(int ml, const char *tail)
+{
+	double vol;
+	const char *unit;
+	int decimals;
+
+	vol = get_volume_units(ml, NULL, &unit);
+	decimals = (vol > 20.0) ? 0 : (vol > 2.0) ? 1 : 2;
+
+	return QString("%1 %2 %3").arg(vol, 0, 'f', decimals).arg(unit).arg(tail);
+}
+
+static QVariant gas_usage_tooltip(cylinder_t *cyl)
+{
+	pressure_t startp = cyl->start.mbar ? cyl->start : cyl->sample_start;
+	pressure_t endp = cyl->end.mbar ? cyl->end : cyl->sample_end;
+
+	int start, end, used;
+
+	start = gas_volume(cyl, startp);
+	end = gas_volume(cyl, endp);
+	used = (end && start > end) ? start - end : 0;
+
+	if (!used)
+		return QVariant();
+
+	return gas_volume_string(used, "(") +
+		gas_volume_string(start, " -> ") +
+		gas_volume_string(end, ")");
+}
+
+static QVariant gas_volume_tooltip(cylinder_t *cyl, pressure_t p)
+{
+	int vol = gas_volume(cyl, p);
+	double Z;
+
+	if (!vol)
+		return QVariant();
+
+	Z = gas_compressibility_factor(&cyl->gasmix, p.mbar / 1000.0);
+	return gas_volume_string(vol, "(Z=") + QString("%1)").arg(Z, 0, 'f', 3);
+}
+
+static QVariant gas_start_tooltip(cylinder_t *cyl)
+{
+	return gas_volume_tooltip(cyl, cyl->start.mbar ? cyl->start : cyl->sample_start);
+}
+
+static QVariant gas_end_tooltip(cylinder_t *cyl)
+{
+	return gas_volume_tooltip(cyl, cyl->end.mbar ? cyl->end : cyl->sample_end);
+}
 
 static QVariant percent_string(fraction_t fraction)
 {
@@ -176,6 +228,13 @@ QVariant CylindersModel::data(const QModelIndex &index, int role) const
 		case REMOVE:
 			ret = tr("Clicking here will remove this cylinder.");
 			break;
+		case SIZE:
+		case WORKINGPRESS:
+			return gas_usage_tooltip(cyl);
+		case START:
+			return gas_start_tooltip(cyl);
+		case END:
+			return gas_end_tooltip(cyl);
 		case DEPTH:
 			ret = tr("Switch depth for deco gas. Calculated using Deco pO₂ preference, unless set manually.");
 			break;