Add a compatibility option to treat cone angles as half angles

All previous versions of the library treated the source cone angles as half
angles, which is contrary to the spec. Setting the __ALSOFT_HALF_ANGLE_CONES
environment variable to "true" or "1" restores the buggy behavior for
compatibility with applications that expect it.

This is not a config file option because new apps should not be made to depend
on the old behavior.

2 files changed, 9 insertions, 2 deletions

diff --git a/Alc/ALc.c b/Alc/ALc.c
index 2dbe52f9..dc781835 100644
--- a/Alc/ALc.c
+++ b/Alc/ALc.c
@@ -384,6 +384,9 @@ static ALint RTPrioLevel;
 // Output Log File
 static FILE *LogFile;
 
+// Cone scalar
+ALdouble ConeScale = 0.5;
+
 ///////////////////////////////////////////////////////
 
 
@@ -435,6 +438,10 @@ static void alc_init(void)
     if(!LogFile)
         LogFile = stderr;
 
+    str = getenv("__ALSOFT_HALF_ANGLE_CONES");
+    if(str && (strcasecmp(str, "true") == 0 || strtol(str, NULL, 0) == 1))
+        ConeScale = 1.0;
+
     InitializeCriticalSection(&g_csMutex);
     ALTHUNK_INIT();
     ReadALConfig();
diff --git a/Alc/ALu.c b/Alc/ALu.c
index ea5a0319..49cedab8 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -357,8 +357,8 @@ ALvoid CalcSourceParams(ALsource *ALSource, const ALCcontext *ALContext)
     MinDist      = ALSource->flRefDistance;
     MaxDist      = ALSource->flMaxDistance;
     Rolloff      = ALSource->flRollOffFactor;
-    InnerAngle   = ALSource->flInnerAngle * 0.5f;
-    OuterAngle   = ALSource->flOuterAngle * 0.5f;
+    InnerAngle   = ALSource->flInnerAngle * ConeScale;
+    OuterAngle   = ALSource->flOuterAngle * ConeScale;
     OuterGainHF  = ALSource->OuterGainHF;
     AirAbsorptionFactor = ALSource->AirAbsorptionFactor;