Add options to reverse local X and Y coordinates

To go along with reverse-z on the other axii. This is only for games that have
position/orientation errors causing top-bottom (or left-right) inversion.

alc/alc.cpp

@@ -1121,14 +1121,20 @@ void alc_initconfig(void)
         AllowRTTimeLimit = *limopt;
 
     CompatFlagBitset compatflags{};
-    if(auto optval = al::getenv("__ALSOFT_REVERSE_Z"))
+    auto checkflag = [](const char *envname, const char *optname) -> bool
     {
-        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);
+        if(auto optval = al::getenv(envname))
+        {
+            if(al::strcasecmp(optval->c_str(), "true") == 0
+                || strtol(optval->c_str(), nullptr, 0) == 1)
+                return true;
+            return false;
+        }
+        return GetConfigValueBool(nullptr, "game_compat", optname, false);
+    };
+    compatflags.set(CompatFlags::ReverseX, checkflag("__ALSOFT_REVERSE_X", "reverse-x"));
+    compatflags.set(CompatFlags::ReverseY, checkflag("__ALSOFT_REVERSE_Y", "reverse-y"));
+    compatflags.set(CompatFlags::ReverseZ, checkflag("__ALSOFT_REVERSE_Z", "reverse-z"));
 
     aluInit(compatflags);
     Voice::InitMixer(ConfigValueStr(nullptr, nullptr, "resampler"));

alc/alu.cpp

@@ -128,9 +128,11 @@ float InitConeScale()
 /* Cone scalar */
 const float ConeScale{InitConeScale()};
 
-/* Localized Z scalar for mono sources (initialized in aluInit, after
+/* Localized scalars for mono sources (initialized in aluInit, after
  * configuration is loaded).
  */
+float XScale{1.0f};
+float YScale{1.0f};
 float ZScale{1.0f};
 
 } // namespace
@@ -245,6 +247,8 @@ inline ResamplerFunc SelectResampler(Resampler resampler, uint increment)
 void aluInit(CompatFlagBitset flags)
 {
     MixDirectHrtf = SelectHrtfMixer();
+    XScale = flags.test(CompatFlags::ReverseX) ? -1.0f : 1.0f;
+    YScale = flags.test(CompatFlags::ReverseY) ? -1.0f : 1.0f;
     ZScale = flags.test(CompatFlags::ReverseZ) ? -1.0f : 1.0f;
 }
 
@@ -1516,7 +1520,7 @@ void CalcAttnSourceParams(Voice *voice, const VoiceProps *props, const ContextBa
     else if(Distance > 0.0f)
         spread = std::asin(props->Radius/Distance) * 2.0f;
 
-    CalcPanningAndFilters(voice, ToSource[0], ToSource[1], ToSource[2]*ZScale,
+    CalcPanningAndFilters(voice, ToSource[0]*XScale, ToSource[1]*YScale, ToSource[2]*ZScale,
         Distance*context->mParams.MetersPerUnit, spread, DryGain, WetGain, SendSlots, props,
         context->mParams, Device);
 }

alc/alu.h

@@ -16,6 +16,8 @@ constexpr float GainMixMax{1000.0f}; /* +60dB */
 
 
 enum CompatFlags : uint8_t {
+    ReverseX,
+    ReverseY,
     ReverseZ,
 
     Count

alsoftrc.sample

@@ -598,6 +598,14 @@
 ##
 [game_compat]
 
+## reverse-x: (global)
+#  Reverses the local X (left-right) position of 3D sound sources.
+#reverse-x = false
+
+## reverse-y: (global)
+#  Reverses the local Y (up-down) position of 3D sound sources.
+#reverse-y = false
+
 ## reverse-z: (global)
 #  Reverses the local Z (front-back) position of 3D sound sources.
 #reverse-z = false

docs/env-vars.txt

@@ -64,8 +64,13 @@ to it before passing in 3D coordinates. Depending on how exactly this is done,
 it can cause correct output for stereo but incorrect Z panning for surround
 sound (i.e., sounds that are supposed to be behind you sound like they're in
 front, and vice-versa). Setting this to "true" or "1" will negate the localized
-Z coordinate to attempt to fix output for apps that have incorrect front/back
-panning.
+Z coordinate to flip front/back panning for 3D sources.
+
+__ALSOFT_REVERSE_Y
+Same as for __ALSOFT_REVERSE_Z, but for Y (up/down) panning.
+
+__ALSOFT_REVERSE_X
+Same as for __ALSOFT_REVERSE_Z, but for X (left/right) panning.
 
 __ALSOFT_SUSPEND_CONTEXT
 Due to the OpenAL spec not being very clear about them, behavior of the