From 005ddf7c9840402d47cab9807c10d13b9d9fb23d Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Wed, 1 Apr 2020 16:20:29 +0100
Subject: [PATCH] Optimisation: avoid property name lookups

---
 src/Main/fg_props.cxx | 34 +++++++++-------------------------
 src/Main/fg_props.hxx |  4 ++++
 2 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/src/Main/fg_props.cxx b/src/Main/fg_props.cxx
index eee6d0006..2ff4ef597 100644
--- a/src/Main/fg_props.cxx
+++ b/src/Main/fg_props.cxx
@@ -326,28 +326,6 @@ getGMTString ()
   return buf;
 }
 
-/**
- * Return the current heading in degrees.
- */
-static double
-getHeadingMag ()
-{
-  double magheading = fgGetDouble("/orientation/heading-deg") -
-    fgGetDouble("/environment/magnetic-variation-deg");
-  return SGMiscd::normalizePeriodic(0, 360, magheading );
-}
-
-/**
- * Return the current track in degrees.
- */
-static double
-getTrackMag ()
-{
-  double magtrack = fgGetDouble("/orientation/track-deg") -
-    fgGetDouble("/environment/magnetic-variation-deg");
-  return SGMiscd::normalizePeriodic(0, 360, magtrack );
-}
-
 ////////////////////////////////////////////////////////////////////////
 // Tie the properties.
 ////////////////////////////////////////////////////////////////////////
@@ -439,9 +417,11 @@ FGProperties::bind ()
   _tiedProperties.Tie<const char*>("/position/latitude-string", getLatitudeString);
   _tiedProperties.Tie<const char*>("/position/longitude-string", getLongitudeString);
 
-  // Orientation
-  _tiedProperties.Tie<double>("/orientation/heading-magnetic-deg", getHeadingMag);
-  _tiedProperties.Tie<double>("/orientation/track-magnetic-deg", getTrackMag);
+    _headingMagnetic = fgGetNode("/orientation/heading-magnetic-deg", true);
+    _trackMagnetic = fgGetNode("/orientation/track-magnetic-deg", true);
+    _magVar = fgGetNode("/environment/magnetic-variation-deg", true);
+    _trueHeading = fgGetNode("/orientatino/heading-deg", true);
+    _trueTrack = fgGetNode("/orientation/track-deg", true);
 }
 
 void
@@ -481,6 +461,10 @@ FGProperties::update (double dt)
     _rmin->setIntValue(r->tm_min);
     _rsec->setIntValue(r->tm_sec);
     _rwday->setIntValue(r->tm_wday);
+    
+    const double magvar = _magVar->getDoubleValue();
+    _headingMagnetic->setDoubleValue(_trueHeading->getDoubleValue() - magvar);
+    _trackMagnetic->setDoubleValue(_trueTrack->getDoubleValue() - magvar);
 }
 
 
diff --git a/src/Main/fg_props.hxx b/src/Main/fg_props.hxx
index 6399ecbbd..a1a021365 100644
--- a/src/Main/fg_props.hxx
+++ b/src/Main/fg_props.hxx
@@ -43,6 +43,10 @@ private:
     SGPropertyNode_ptr _offset;
     SGPropertyNode_ptr _uyear, _umonth, _uday, _uhour, _umin, _usec, _uwday, _udsec;
     SGPropertyNode_ptr _ryear, _rmonth, _rday, _rhour, _rmin, _rsec, _rwday, _rdsec;
+    
+    SGPropertyNode_ptr _headingMagnetic, _trackMagnetic;
+    SGPropertyNode_ptr _magVar;
+    SGPropertyNode_ptr _trueHeading, _trueTrack;
 };