From 609ee742115aa10139d5e4c3f8915306751c227f Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Thu, 10 Mar 2022 17:47:42 -0800
Subject: Add a config option for reverse-z

The same as the __ALSOFT_REVERSE_Z env var, but in the config file. Should only
be used for per-game config files (either along side the executable, or setting
the ALSOFT_CONF env var when launching the app).
---
 alc/alc.cpp     | 12 +++++++++++-
 alc/alu.cpp     | 26 ++++++++------------------
 alc/alu.h       | 15 ++++++++++-----
 alsoftrc.sample | 13 ++++++++++++-
 4 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/alc/alc.cpp b/alc/alc.cpp
index 90da2614..4ba47aea 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -1120,7 +1120,17 @@ void alc_initconfig(void)
     if(auto limopt = ConfigValueBool(nullptr, nullptr, "rt-time-limit"))
         AllowRTTimeLimit = *limopt;
 
-    aluInit();
+    CompatFlagBitset compatflags{};
+    if(auto optval = al::getenv("__ALSOFT_REVERSE_Z"))
+    {
+        if(al::strcasecmp(optval->c_str(), "true") == 0
+            || strtol(optval->c_str(), nullptr, 0) == 1)
+            compatflags.set(CompatFlags::ReverseZ);
+    }
+    else if(GetConfigValueBool(nullptr, "game_compat", "reverse-z", false))
+        compatflags.set(CompatFlags::ReverseZ);
+
+    aluInit(compatflags);
     Voice::InitMixer(ConfigValueStr(nullptr, nullptr, "resampler"));
 
     auto traperr = al::getenv("ALSOFT_TRAP_ERROR");
diff --git a/alc/alu.cpp b/alc/alu.cpp
index 67727bd5..203fd9b6 100644
--- a/alc/alu.cpp
+++ b/alc/alu.cpp
@@ -125,26 +125,15 @@ float InitConeScale()
     }
     return ret;
 }
-
-float InitZScale()
-{
-    float ret{1.0f};
-    if(auto optval = al::getenv("__ALSOFT_REVERSE_Z"))
-    {
-        if(al::strcasecmp(optval->c_str(), "true") == 0
-            || strtol(optval->c_str(), nullptr, 0) == 1)
-            ret *= -1.0f;
-    }
-    return ret;
-}
-
-} // namespace
-
 /* Cone scalar */
 const float ConeScale{InitConeScale()};
 
-/* Localized Z scalar for mono sources */
-const float ZScale{InitZScale()};
+/* Localized Z scalar for mono sources (initialized in aluInit, after
+ * configuration is loaded).
+ */
+float ZScale{1.0f};
+
+} // namespace
 
 namespace {
 
@@ -253,9 +242,10 @@ inline ResamplerFunc SelectResampler(Resampler resampler, uint increment)
 
 } // namespace
 
-void aluInit(void)
+void aluInit(CompatFlagBitset flags)
 {
     MixDirectHrtf = SelectHrtfMixer();
+    ZScale = flags.test(CompatFlags::ReverseZ) ? -1.0f : 1.0f;
 }
 
 
diff --git a/alc/alu.h b/alc/alu.h
index b88f7cf5..03f56f56 100644
--- a/alc/alu.h
+++ b/alc/alu.h
@@ -1,6 +1,8 @@
 #ifndef ALU_H
 #define ALU_H
 
+#include <bitset>
+
 #include "aloptional.h"
 
 struct ALCcontext;
@@ -13,7 +15,14 @@ enum class StereoEncoding : unsigned char;
 constexpr float GainMixMax{1000.0f}; /* +60dB */
 
 
-void aluInit(void);
+enum CompatFlags : uint8_t {
+    ReverseZ,
+
+    Count
+};
+using CompatFlagBitset = std::bitset<CompatFlags::Count>;
+
+void aluInit(CompatFlagBitset flags);
 
 /* aluInitRenderer
  *
@@ -24,8 +33,4 @@ void aluInitRenderer(ALCdevice *device, int hrtf_id, al::optional<StereoEncoding
 
 void aluInitEffectPanning(EffectSlot *slot, ALCcontext *context);
 
-
-extern const float ConeScale;
-extern const float ZScale;
-
 #endif
diff --git a/alsoftrc.sample b/alsoftrc.sample
index ab0345d9..eebd3de7 100644
--- a/alsoftrc.sample
+++ b/alsoftrc.sample
@@ -583,6 +583,17 @@
 ## EAX extensions stuff
 ##
 [eax]
-##enable:
+
+## enable: (global)
 #  Sets whether to enable EAX extensions or not.
 #enable = true
+
+##
+## Per-game compatibility options (these should only be set in per-game config
+## files, *NOT* system- or user-level!)
+##
+[game_compat]
+
+## reverse-z: (global)
+#  Reverses the local Z (front-back) position of 3D sound sources.
+#reverse-z = false
-- 
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