C64: add chip flag to set env reset time

2 by default
1 for .dmf and old Furnace songs

src/engine/fileOps.cpp

@@ -1062,9 +1062,10 @@ bool DivEngine::loadDMF(unsigned char* file, size_t len) {
       ds.systemFlags[0].set("dpcmMode",false);
     }
 
-    // C64 no key priority
+    // C64 no key priority and reset time
     if (ds.system[0]==DIV_SYSTEM_C64_8580 || ds.system[0]==DIV_SYSTEM_C64_6581) {
       ds.systemFlags[0].set("keyPriority",false);
+      ds.systemFlags[0].set("initResetTime",1);
     }
 
     // OPM broken pitch
@@ -3033,6 +3034,15 @@ bool DivEngine::loadFur(unsigned char* file, size_t len) {
       }
     }
 
+    // C64 original reset time
+    if (ds.version<187) {
+      for (int i=0; i<ds.systemLen; i++) {
+        if (ds.system[i]==DIV_SYSTEM_C64_8580 || ds.system[i]==DIV_SYSTEM_C64_6581) {
+          ds.systemFlags[i].set("initResetTime",1);
+        }
+      }
+    }
+
     if (active) quitDispatch();
     BUSY_BEGIN_SOFT;
     saveLock.lock();

src/engine/platform/c64.cpp

@@ -678,7 +678,7 @@ void DivPlatformC64::reset() {
   filtControl=7;
   filtRes=0;
   filtCut=2047;
-  resetTime=1;
+  resetTime=initResetTime;
   vol=15;
 
   chanOrder[0]=0;
@@ -728,6 +728,8 @@ void DivPlatformC64::setFlags(const DivConfig& flags) {
   no1EUpdate=flags.getBool("no1EUpdate",false);
   testAD=((flags.getInt("testAttack",0)&15)<<4)|(flags.getInt("testDecay",0)&15);
   testSR=((flags.getInt("testSustain",0)&15)<<4)|(flags.getInt("testRelease",0)&15);
+  initResetTime=flags.getInt("initResetTime",2);
+  if (initResetTime<0) initResetTime=1;
 
   // init fake filter table
   // taken from dSID

src/engine/platform/c64.h

@@ -75,7 +75,7 @@ class DivPlatformC64: public DivDispatch {
   unsigned char filtControl, filtRes, vol;
   unsigned char writeOscBuf;
   unsigned char sidCore;
-  int filtCut, resetTime;
+  int filtCut, resetTime, initResetTime;
 
   bool keyPriority, sidIs6581, needInitTables, no1EUpdate;
   unsigned char chanOrder[3];

src/gui/sysConf.cpp

@@ -591,6 +591,7 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       int testDecay=flags.getInt("testDecay",0);
       int testSustain=flags.getInt("testSustain",0);
       int testRelease=flags.getInt("testRelease",0);
+      int initResetTime=flags.getInt("initResetTime",2);
 
       ImGui::Text("Clock rate:");
 
@@ -645,6 +646,18 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
         altered=true;
       }
 
+      ImGui::Text("Envelope reset time:");
+
+      pushWarningColor(initResetTime<1 || initResetTime>4);
+      if (CWSliderInt("##InitReset",&initResetTime,0,16)) {
+        if (initResetTime<0) initResetTime=0;
+        if (initResetTime>16) initResetTime=16;
+        altered=true;
+      }
+      popWarningColor();
+      
+      ImGui::Text("- 0 disables envelope reset. not recommended!\n- 1 may trigger SID envelope bugs.\n- values that are too high may result in notes being skipped.");
+
       if (ImGui::Checkbox("Disable 1Exy env update (compatibility)",&no1EUpdate)) {
         altered=true;
       }
@@ -658,6 +671,7 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
           flags.set("testDecay",testDecay);
           flags.set("testSustain",testSustain);
           flags.set("testRelease",testRelease);
+          flags.set("initResetTime",initResetTime);
         });
       }
       break;