From ec69c30ca0f3dde7a1248ef7dd49e105c8e24d72 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Sat, 21 Jun 2025 21:39:29 -0500
Subject: [PATCH] NES: here's your FamiTracker compatibility flag

---
 src/engine/fileOps/ftm.cpp  |  1 +
 src/engine/platform/nes.cpp | 12 +++++++++---
 src/engine/platform/nes.h   |  1 +
 src/gui/sysConf.cpp         |  6 ++++++
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/engine/fileOps/ftm.cpp b/src/engine/fileOps/ftm.cpp
index 35bca5f38..f1ee0eb15 100644
--- a/src/engine/fileOps/ftm.cpp
+++ b/src/engine/fileOps/ftm.cpp
@@ -655,6 +655,7 @@ bool DivEngine::loadFTM(unsigned char* file, size_t len, bool dnft, bool dnft_si
         int map_ch = 0;
 
         ds.system[systemID++] = DIV_SYSTEM_NES;
+        ds.systemFlags[0].set("resetSweep",true); // FamiTracker behavior
 
         if (pal) {
           ds.systemFlags[0].set("clockSel", 1); // PAL clock
diff --git a/src/engine/platform/nes.cpp b/src/engine/platform/nes.cpp
index 8d4fd8cc0..5513f2996 100644
--- a/src/engine/platform/nes.cpp
+++ b/src/engine/platform/nes.cpp
@@ -352,9 +352,6 @@ void DivPlatformNES::tick(bool sysTick) {
     }
     if (chan[i].sweepChanged) {
       chan[i].sweepChanged=false;
-      if (i==0) {
-        // rWrite(16+i*5,chan[i].sweep);
-      }
     }
     if (i<3) if (chan[i].std.phaseReset.had) {
       if (chan[i].std.phaseReset.val==1) {
@@ -637,6 +634,13 @@ int DivPlatformNES::dispatch(DivCommand c) {
       } else if (!parent->song.brokenOutVol2) {
         rWrite(0x4000+c.chan*4,(chan[c.chan].envMode<<4)|chan[c.chan].vol|((chan[c.chan].duty&3)<<6));
       }
+      if (resetSweep && c.chan<2) {
+        if (chan[c.chan].sweep!=0x08 && !chan[c.chan].sweepChanged) {
+          chan[c.chan].sweep=0x08;
+          chan[c.chan].prevFreq=-1;
+          rWrite(0x4001+(c.chan*4),chan[c.chan].sweep);
+        }
+      }
       break;
     case DIV_CMD_NOTE_OFF:
       if (c.chan==4) {
@@ -724,6 +728,7 @@ int DivPlatformNES::dispatch(DivCommand c) {
         }
       }
       rWrite(0x4001+(c.chan*4),chan[c.chan].sweep);
+      chan[c.chan].sweepChanged=true;
       break;
     case DIV_CMD_NES_ENV_MODE:
       chan[c.chan].envMode=c.value&3;
@@ -989,6 +994,7 @@ void DivPlatformNES::setFlags(const DivConfig& flags) {
   }
   
   dpcmModeDefault=flags.getBool("dpcmMode",true);
+  resetSweep=flags.getBool("resetSweep",false);
 }
 
 void DivPlatformNES::notifyInsDeletion(void* ins) {
diff --git a/src/engine/platform/nes.h b/src/engine/platform/nes.h
index 7c0a10aeb..5ab205ef0 100644
--- a/src/engine/platform/nes.h
+++ b/src/engine/platform/nes.h
@@ -68,6 +68,7 @@ class DivPlatformNES: public DivDispatch {
   signed char lastDPCMFreq;
   bool dpcmMode;
   bool dpcmModeDefault;
+  bool resetSweep;
   bool dacAntiClickOn;
   bool useNP;
   bool goingToLoop;
diff --git a/src/gui/sysConf.cpp b/src/gui/sysConf.cpp
index b36e5f32a..3b6a5d977 100644
--- a/src/gui/sysConf.cpp
+++ b/src/gui/sysConf.cpp
@@ -611,6 +611,7 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
     case DIV_SYSTEM_5E01: {
       int clockSel=flags.getInt("clockSel",0);
       bool dpcmMode=flags.getBool("dpcmMode",true);
+      bool resetSweep=flags.getBool("resetSweep",false);
 
       ImGui::Text(_("Clock rate:"));
 
@@ -642,10 +643,15 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       }
       ImGui::Unindent();
 
+      if (ImGui::Checkbox(_("Reset sweep on new note"),&resetSweep)) {
+        altered=true;
+      }
+
       if (altered) {
         e->lockSave([&]() {
           flags.set("clockSel",clockSel);
           flags.set("dpcmMode",dpcmMode);
+          flags.set("resetSweep",resetSweep);
         });
       }
       break;