From b037b07c30b503769e55b54f86cae1ebfb4389a9 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Thu, 4 May 2023 16:49:47 -0500
Subject: [PATCH] SNES: add global volume control effects

---
 papers/doc/7-systems/snes.md |  4 ++++
 src/engine/dispatch.h        |  3 +++
 src/engine/platform/snes.cpp | 18 ++++++++++++++++++
 src/engine/platform/snes.h   |  2 ++
 src/engine/playback.cpp      |  3 +++
 src/engine/sysDef.cpp        |  2 ++
 6 files changed, 32 insertions(+)

diff --git a/papers/doc/7-systems/snes.md b/papers/doc/7-systems/snes.md
index a2ecd9aee..61b30635d 100644
--- a/papers/doc/7-systems/snes.md
+++ b/papers/doc/7-systems/snes.md
@@ -54,6 +54,10 @@ Furnace also allows the SNES to use wavetables (and the wavetable synthesizer) i
   - 80 to FF for -128 to -1.
     - setting this to -128 is not recommended as it may cause echo output to overflow and therefore click.
 - `1Dxx`: set noise generator frequency (00 to 1F).
+- `1Exx`: set left dry/global volume.
+  - this does not affect echo.
+- `1Fxx`: set right dry/global volume.
+  - this does not affect echo.
 - `20xx`: set attack (0 to F).
   - only in ADSR envelope mode.
 - `21xx`: set decay (0 to 7).
diff --git a/src/engine/dispatch.h b/src/engine/dispatch.h
index 0c9d2ca74..0f075e56c 100644
--- a/src/engine/dispatch.h
+++ b/src/engine/dispatch.h
@@ -231,6 +231,9 @@ enum DivDispatchCmds {
 
   DIV_CMD_HINT_ARP_TIME, // (value)
 
+  DIV_CMD_SNES_GLOBAL_VOL_LEFT,
+  DIV_CMD_SNES_GLOBAL_VOL_RIGHT,
+
   DIV_ALWAYS_SET_VOLUME, // () -> alwaysSetVol
 
   DIV_CMD_MAX
diff --git a/src/engine/platform/snes.cpp b/src/engine/platform/snes.cpp
index 48351493c..a5684d0e8 100644
--- a/src/engine/platform/snes.cpp
+++ b/src/engine/platform/snes.cpp
@@ -300,6 +300,11 @@ void DivPlatformSNES::tick(bool sysTick) {
     rWrite(0x4d,echoBits);
     writeEcho=false;
   }
+  if (writeDryVol) {
+    rWrite(0x0c,dryVolL);
+    rWrite(0x1c,dryVolR);
+    writeDryVol=false;
+  }
   for (int i=0; i<8; i++) {
     if (chan[i].shallWriteEnv) {
       writeEnv(i);
@@ -563,6 +568,14 @@ int DivPlatformSNES::dispatch(DivCommand c) {
         rWrite(0x3c,echoVolR);
       }
       break;
+    case DIV_CMD_SNES_GLOBAL_VOL_LEFT:
+      dryVolL=c.value;
+      writeDryVol=true;
+      break;
+    case DIV_CMD_SNES_GLOBAL_VOL_RIGHT:
+      dryVolR=c.value;
+      writeDryVol=true;
+      break;
     case DIV_CMD_GET_VOLMAX:
       return 127;
       break;
@@ -673,6 +686,7 @@ void DivPlatformSNES::forceIns() {
   writeNoise=true;
   writePitchMod=true;
   writeEcho=true;
+  writeDryVol=true;
   initEcho();
 }
 
@@ -761,6 +775,10 @@ void DivPlatformSNES::reset() {
   writeNoise=false;
   writePitchMod=false;
   writeEcho=true;
+  writeDryVol=false;
+
+  dryVolL=127;
+  dryVolR=127;
 
   echoDelay=initEchoDelay;
   echoFeedback=initEchoFeedback;
diff --git a/src/engine/platform/snes.h b/src/engine/platform/snes.h
index 3c3426466..68637be82 100644
--- a/src/engine/platform/snes.h
+++ b/src/engine/platform/snes.h
@@ -59,6 +59,7 @@ class DivPlatformSNES: public DivDispatch {
   unsigned char noiseFreq;
   signed char delay;
   signed char echoVolL, echoVolR, echoFeedback;
+  signed char dryVolL, dryVolR;
   signed char echoFIR[8];
   unsigned char echoDelay;
   size_t sampleTableBase;
@@ -66,6 +67,7 @@ class DivPlatformSNES: public DivDispatch {
   bool writeNoise;
   bool writePitchMod;
   bool writeEcho;
+  bool writeDryVol;
   bool echoOn;
 
   bool initEchoOn;
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index 8cc2f825f..114288827 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -231,6 +231,9 @@ const char* cmdName[]={
 
   "HINT_ARP_TIME",
 
+  "SNES_GLOBAL_VOL_LEFT",
+  "SNES_GLOBAL_VOL_RIGHT",
+
   "ALWAYS_SET_VOLUME"
 };
 
diff --git a/src/engine/sysDef.cpp b/src/engine/sysDef.cpp
index d92573bb7..42fab2cbf 100644
--- a/src/engine/sysDef.cpp
+++ b/src/engine/sysDef.cpp
@@ -911,6 +911,8 @@ void DivEngine::registerSystems() {
       {0x1a, {DIV_CMD_SNES_ECHO_VOL_LEFT, "1Axx: Set left echo volume"}},
       {0x1b, {DIV_CMD_SNES_ECHO_VOL_RIGHT, "1Bxx: Set right echo volume"}},
       {0x1c, {DIV_CMD_SNES_ECHO_FEEDBACK, "1Cxx: Set echo feedback"}},
+      {0x1e, {DIV_CMD_SNES_GLOBAL_VOL_LEFT, "1Exx: Set dry output volume (left)"}},
+      {0x1f, {DIV_CMD_SNES_GLOBAL_VOL_RIGHT, "1Fxx: Set dry output volume (right)"}},
       {0x30, {DIV_CMD_SNES_ECHO_FIR, "30xx: Set echo filter coefficient 0",constVal<0>,effectVal}},
       {0x31, {DIV_CMD_SNES_ECHO_FIR, "31xx: Set echo filter coefficient 1",constVal<1>,effectVal}},
       {0x32, {DIV_CMD_SNES_ECHO_FIR, "32xx: Set echo filter coefficient 2",constVal<2>,effectVal}},