From bd68ef5cc3efdc439aa7f7418dc8028f65f6d106 Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Sun, 24 Apr 2022 18:12:18 -0500
Subject: [PATCH] dev86 - SN duty macro phase reset fix

---
 papers/format.md            |  4 +++-
 src/engine/engine.h         |  4 ++--
 src/engine/fileOps.cpp      | 14 ++++++++++++--
 src/engine/platform/sms.cpp | 10 ++++++----
 src/engine/song.h           |  4 +++-
 src/gui/compatFlags.cpp     |  4 ++++
 6 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/papers/format.md b/papers/format.md
index ef8ab7e50..207b232aa 100644
--- a/papers/format.md
+++ b/papers/format.md
@@ -29,6 +29,7 @@ furthermore, an `or reserved` indicates this field is always present, but is res
 
 the format versions are:
 
+- 86: Furnace dev86
 - 85: Furnace dev85
 - 84: Furnace dev84
 - 83: Furnace dev83
@@ -273,7 +274,8 @@ size | description
   1  | E1xx and E2xx also take priority over Slide00 (>=83) or reserved
   1  | new Sega PCM (with macros and proper vol/pan) (>=84) or reserved
   1  | weird f-num/block-based chip pitch slides (>=85) or reserved
- 21  | reserved
+  1  | SN duty macro always resets phase (>=86) or reserved
+ 20  | reserved
 ```
 
 # instrument
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 427215df0..3bd1db3dc 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -43,8 +43,8 @@
 #define BUSY_BEGIN_SOFT softLocked=true; isBusy.lock();
 #define BUSY_END isBusy.unlock(); softLocked=false;
 
-#define DIV_VERSION "dev85"
-#define DIV_ENGINE_VERSION 85
+#define DIV_VERSION "dev86"
+#define DIV_ENGINE_VERSION 86
 
 // for imports
 #define DIV_VERSION_MOD 0xff01
diff --git a/src/engine/fileOps.cpp b/src/engine/fileOps.cpp
index 48ef68bba..38b33502b 100644
--- a/src/engine/fileOps.cpp
+++ b/src/engine/fileOps.cpp
@@ -163,6 +163,7 @@ bool DivEngine::loadDMF(unsigned char* file, size_t len) {
     ds.ignoreDACModeOutsideIntendedChannel=false;
     ds.e1e2AlsoTakePriority=true;
     ds.fbPortaPause=true;
+    ds.snDutyReset=true;
 
     // 1.1 compat flags
     if (ds.version>24) {
@@ -997,6 +998,9 @@ bool DivEngine::loadFur(unsigned char* file, size_t len) {
     if (ds.version<85) {
       ds.fbPortaPause=true;
     }
+    if (ds.version<86) {
+      ds.snDutyReset=true;
+    }
     ds.isDMF=false;
 
     reader.readS(); // reserved
@@ -1351,7 +1355,12 @@ bool DivEngine::loadFur(unsigned char* file, size_t len) {
       } else {
         reader.readC();
       }
-      for (int i=0; i<21; i++) {
+      if (ds.version>=86) {
+        ds.snDutyReset=reader.readC();
+      } else {
+        reader.readC();
+      }
+      for (int i=0; i<20; i++) {
         reader.readC();
       }
     }
@@ -2293,7 +2302,8 @@ SafeWriter* DivEngine::saveFur(bool notPrimary) {
   w->writeC(song.e1e2AlsoTakePriority);
   w->writeC(song.newSegaPCM);
   w->writeC(song.fbPortaPause);
-  for (int i=0; i<21; i++) {
+  w->writeC(song.snDutyReset);
+  for (int i=0; i<20; i++) {
     w->writeC(0);
   }
 
diff --git a/src/engine/platform/sms.cpp b/src/engine/platform/sms.cpp
index af339f6e2..c32548b56 100644
--- a/src/engine/platform/sms.cpp
+++ b/src/engine/platform/sms.cpp
@@ -86,11 +86,13 @@ void DivPlatformSMS::tick(bool sysTick) {
     }
     if (i==3) {
       if (chan[i].std.duty.had) {
-        snNoiseMode=chan[i].std.duty.val;
-        if (chan[i].std.duty.val<2) {
-          chan[3].freqChanged=false;
+        if (chan[i].std.duty.val!=snNoiseMode || parent->song.snDutyReset) {
+          snNoiseMode=chan[i].std.duty.val;
+          if (chan[i].std.duty.val<2) {
+            chan[3].freqChanged=false;
+          }
+          updateSNMode=true;
         }
-        updateSNMode=true;
       }
       if (chan[i].std.phaseReset.had) {
         if (chan[i].std.phaseReset.val==1) {
diff --git a/src/engine/song.h b/src/engine/song.h
index 11264558b..7c06a14a5 100644
--- a/src/engine/song.h
+++ b/src/engine/song.h
@@ -325,6 +325,7 @@ struct DivSong {
   bool e1e2AlsoTakePriority;
   bool newSegaPCM;
   bool fbPortaPause;
+  bool snDutyReset;
 
   DivOrders orders;
   std::vector<DivInstrument*> ins;
@@ -429,7 +430,8 @@ struct DivSong {
     ignoreDACModeOutsideIntendedChannel(false),
     e1e2AlsoTakePriority(false),
     newSegaPCM(true),
-    fbPortaPause(false) {
+    fbPortaPause(false),
+    snDutyReset(false) {
     for (int i=0; i<32; i++) {
       system[i]=DIV_SYSTEM_NULL;
       systemVol[i]=64;
diff --git a/src/gui/compatFlags.cpp b/src/gui/compatFlags.cpp
index 8d1fd6d18..ccaeeb3fe 100644
--- a/src/gui/compatFlags.cpp
+++ b/src/gui/compatFlags.cpp
@@ -117,6 +117,10 @@ void FurnaceGUI::drawCompatFlags() {
     if (ImGui::IsItemHovered()) {
       ImGui::SetTooltip("does this make any sense by now?");
     }
+    ImGui::Checkbox("SN76489 duty macro always resets phase",&e->song.snDutyReset);
+    if (ImGui::IsItemHovered()) {
+      ImGui::SetTooltip("when enabled, duty macro will always reset phase, even if its value hasn't changed.");
+    }
 
     ImGui::Text("Loop modality:");
     if (ImGui::RadioButton("Reset channels",e->song.loopModality==0)) {