From 93237f1b379a536554fa5eaabd7ba1861c609ea4 Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Mon, 19 Nov 2012 23:17:03 +0000
Subject: [PATCH] Avoid a dependency on the environment-manager.

Change the ASI Mach computation (written by me) to use properties, instead of depending directly on the environment-manager.
---
 src/Instrumentation/airspeed_indicator.cxx | 20 +++++++-------------
 src/Instrumentation/airspeed_indicator.hxx |  7 ++-----
 2 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/src/Instrumentation/airspeed_indicator.cxx b/src/Instrumentation/airspeed_indicator.cxx
index a3ff2df4e..223c4d774 100644
--- a/src/Instrumentation/airspeed_indicator.cxx
+++ b/src/Instrumentation/airspeed_indicator.cxx
@@ -14,8 +14,6 @@
 #include "airspeed_indicator.hxx"
 #include <Main/fg_props.hxx>
 #include <Main/util.hxx>
-#include <Environment/environment_mgr.hxx>
-#include <Environment/environment.hxx>
 
 
 // A higher number means more responsive.
@@ -33,7 +31,6 @@ AirspeedIndicator::AirspeedIndicator ( SGPropertyNode *node )
     _mach_limit(node->getDoubleValue("mach-limit", 0.48)),
     _alt_threshold(node->getDoubleValue("alt-threshold", 13200))
 {
-  _environmentManager = NULL;
 }
 
 AirspeedIndicator::~AirspeedIndicator ()
@@ -51,6 +48,10 @@ AirspeedIndicator::init ()
     _total_pressure_node = fgGetNode(_total_pressure.c_str(), true);
     _static_pressure_node = fgGetNode(_static_pressure.c_str(), true);
     _density_node = fgGetNode("/environment/density-slugft3", true);
+    
+    _sea_level_pressure_node = fgGetNode("/environment/pressure-sea-level-inhg", true);
+    _oat_celsius_node = fgGetNode("/environment/temperature-degc", true);
+  
     _speed_node = node->getChild("indicated-speed-kt", 0, true);
     _tas_node = node->getChild("true-speed-kt", 0, true);
     _mach_node = node->getChild("indicated-mach", 0, true);
@@ -76,8 +77,6 @@ AirspeedIndicator::init ()
         _airspeed_limit = node->getChild("airspeed-limit-kt", 0, true);
         _pressure_alt = fgGetNode(_pressure_alt_source.c_str(), true);
     }
-    
-    _environmentManager = (FGEnvironmentMgr*) globals->get_subsystem("environment");
 }
 
 void
@@ -136,19 +135,14 @@ AirspeedIndicator::update (double dt)
 void
 AirspeedIndicator::computeMach(double ias)
 {
-  if (!_environmentManager) {
-    return;
-  }
-  
-  FGEnvironment env(_environmentManager->getEnvironment());
-  
+   
   // derived from http://williams.best.vwh.net/avform.htm#Mach
   // names here are picked to be consistent with those formulae!
 
-  double oatK = env.get_temperature_degc() + 273.15; // OAT in Kelvin
+  double oatK = _oat_celsius_node->getDoubleValue() + 273.15; // OAT in Kelvin
   double CS = 38.967854 * sqrt(oatK); // speed-of-sound in knots at altitude
   double CS_0 = 661.4786; // speed-of-sound in knots at sea-level
-  double P_0 = env.get_pressure_sea_level_inhg();
+  double P_0 = _sea_level_pressure_node->getDoubleValue();
   double P = _static_pressure_node->getDoubleValue();
   
   double DP = P_0 * (pow(1 + 0.2*pow(ias/CS_0, 2), 3.5) - 1);
diff --git a/src/Instrumentation/airspeed_indicator.hxx b/src/Instrumentation/airspeed_indicator.hxx
index e85a8ffbd..0a35406ae 100644
--- a/src/Instrumentation/airspeed_indicator.hxx
+++ b/src/Instrumentation/airspeed_indicator.hxx
@@ -14,9 +14,6 @@
 #include <simgear/props/props.hxx>
 #include <simgear/structure/subsystem_mgr.hxx>
 
-// forward decls
-class FGEnvironmentMgr;
-
 /**
  * Model an airspeed indicator tied to the pitot and static ports.
  *
@@ -68,8 +65,8 @@ private:
     SGPropertyNode_ptr _pressure_alt;
     SGPropertyNode_ptr _mach_node;
     SGPropertyNode_ptr _tas_node;
-    
-    FGEnvironmentMgr* _environmentManager;
+    SGPropertyNode_ptr _sea_level_pressure_node;
+    SGPropertyNode_ptr _oat_celsius_node;
 };
 
 #endif // __INSTRUMENTS_AIRSPEED_INDICATOR_HXX