Refine and unify late RESx during hblank, comments.

src/emucore/tia/Ball.cxx

@@ -69,9 +69,9 @@ void Ball::hmbl(uInt8 value)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void Ball::resbl(bool hblank, bool extendedHblank)
+void Ball::resbl(uInt8 counter)
 {
-  myCounter = hblank ? (extendedHblank ? 158 : 159) : 157;
+  myCounter = counter;
 
   myIsRendering = true;
   myRenderCounter = Count::renderCounterOffset;

src/emucore/tia/Ball.hxx

@@ -39,7 +39,7 @@ class Ball : public Serializable
     void hmbl(uInt8 value);
     uInt8 hmbl() const { return myHmmClocks; }
 
-    void resbl(bool hblank, bool extendedHblank);
+    void resbl(uInt8 counter);
 
     void ctrlpf(uInt8 value);
 

src/emucore/tia/Missile.cxx

@@ -69,9 +69,9 @@ void Missile::hmm(uInt8 value)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void Missile::resm(bool hblank, bool extendedHblank)
+void Missile::resm(uInt8 counter)
 {
-  myCounter = hblank ? (extendedHblank ? 158 : 159) : 157;
+  myCounter = counter;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/emucore/tia/Missile.hxx

@@ -39,7 +39,7 @@ class Missile : public Serializable
     void hmm(uInt8 value);
     uInt32 hmm() const { return myHmmClocks; }
 
-    void resm(bool hblank, bool extendHblank);
+    void resm(uInt8 counter);
 
     void resmp(uInt8 value, const Player& player);
     bool resmp() const { return bool(myResmp); }

src/emucore/tia/Player.cxx

@@ -88,6 +88,8 @@ void Player::nusiz(uInt8 value)
   if (myIsRendering && myRenderCounter >= myWidth)
     myIsRendering = false;
 
+  // NUSIZ during decode seems to affect the decoding logic. The rods in Meltdown
+  // are highly sensitive to this effect, and this seems to model it adequately.
   if (myIsRendering && myRenderCounter < 0 && myWidth > 8 && oldWidth == 8)
     myRenderCounter += (myRenderCounter < -2 ? -1 : 1);
 
@@ -95,12 +97,14 @@ void Player::nusiz(uInt8 value)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void Player::resp(bool hblank, bool extendedHblank)
+void Player::resp(uInt8 counter)
 {
-  myCounter = hblank ? (extendedHblank ? 158 : 159) : 157;
+  myCounter = counter;
 
   const Int8 renderCounterOffset = myWidth > 8 ? Count::renderCounterOffsetWide : Count::renderCounterOffset;
 
+  // This tries to account for the effects of RESP during draw counter decode as
+  // described in Andrew Towers' notes. Still room for tuning.'
   if (myIsRendering && (myRenderCounter - renderCounterOffset) < 4)
     myRenderCounter = renderCounterOffset;
 }

src/emucore/tia/Player.hxx

@@ -40,7 +40,7 @@ class Player : public Serializable
 
     void nusiz(uInt8 value);
 
-    void resp(bool hblank, bool extendedHblank);
+    void resp(uInt8 counter);
 
     void refp(uInt8 value);
     bool refp() const { return myIsReflected; }

src/emucore/tia/TIA.cxx

@@ -57,6 +57,17 @@ enum DummyRegisters: uInt8 {
   shuffleBL = 0xF2
 };
 
+enum ResxCounter: uInt8 {
+  hblank = 159,
+  lateHblank = 158,
+  frame = 157
+};
+
+// This parameter still has room for tuning. If we go lower than 73, long005 will show
+// a slight artifact (still have to crosscheck on real hardware), if we go lower than
+// 70, the G.I. Joe will show an artifact (hole in roof).
+static constexpr uInt8 resxLateHblankThreshold = 73;
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 TIA::TIA(Console& console, Sound& sound, Settings& settings)
   : myConsole(console),
@@ -451,12 +462,12 @@ bool TIA::poke(uInt16 address, uInt8 value)
 
     case RESM0:
       myLinesSinceChange = 0;
-      myMissile0.resm(myHstate == HState::blank, myHctr >= 68);
+      myMissile0.resm(resxCounter());
       break;
 
     case RESM1:
       myLinesSinceChange = 0;
-      myMissile1.resm(myHstate == HState::blank, myHctr >= 68);
+      myMissile1.resm(resxCounter());
       break;
 
     case RESMP0:
@@ -520,12 +531,12 @@ bool TIA::poke(uInt16 address, uInt8 value)
 
     case RESP0:
       myLinesSinceChange = 0;
-      myPlayer0.resp(myHstate == HState::blank, myHctr >= 68);
+      myPlayer0.resp(resxCounter());
       break;
 
     case RESP1:
       myLinesSinceChange = 0;
-      myPlayer1.resp(myHstate == HState::blank, myHctr >= 68);
+      myPlayer1.resp(resxCounter());
       break;
 
     case REFP0:
@@ -560,7 +571,7 @@ bool TIA::poke(uInt16 address, uInt8 value)
 
     case RESBL:
       myLinesSinceChange = 0;
-      myBall.resbl(myHstate == HState::blank, myHctr >= 68);
+      myBall.resbl(resxCounter());
       break;
 
     case VDELBL:
@@ -1235,6 +1246,13 @@ void TIA::updatePaddle(uInt8 idx)
                               myTimestamp, myFrameManager.tvMode());
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+uInt8 TIA::resxCounter()
+{
+  return myHstate == HState::blank ?
+    (myHctr >= resxLateHblankThreshold ? ResxCounter::lateHblank : ResxCounter::hblank) : ResxCounter::frame;
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt8 TIA::collCXM0P() const
 {

src/emucore/tia/TIA.hxx

@@ -380,6 +380,8 @@ class TIA : public Device
 
     void updatePaddle(uInt8 idx);
 
+    uInt8 resxCounter();
+
     /**
       Get the result of the specified collision register.
     */