Fix garbage for ROMs with varying visible frame heights:

* Keep track of max frame height
  * Blank out any missing scanlines
  * Refactoring

src/emucore/tia/FrameManager.cxx

@@ -17,6 +17,8 @@
 
 // #define TIA_FRAMEMANAGER_DEBUG_LOG
 
+#include <algorithm>
+
 #include "FrameManager.hxx"
 
 enum Metrics: uInt32 {
@@ -65,6 +67,7 @@ void FrameManager::reset()
   myCurrentFrameTotalLines = myCurrentFrameFinalLines = 0;
   myFrameRate = 60.0;
   myLineInState = 0;
+  myMaxVisibleFrameLines = 0;
   myVsync = false;
   myVblank = false;
   myTotalFrames = 0;
@@ -141,14 +144,15 @@ void FrameManager::nextLineInVsync()
         }
 
         setState(State::frame);
-    } else if (shouldTransition){
-      if (!myVblankViolated) myVblankViolations++;
-      myVblankViolated = true;
-    }
+      } else if (shouldTransition){
+        if (!myVblankViolated) myVblankViolations++;
+        myVblankViolated = true;
+      }
 
-    if (myVblankViolations > Metrics::maxVblankViolations)
-      myVblankMode = VblankMode::floating;
+      if (myVblankViolations > Metrics::maxVblankViolations)
+        myVblankMode = VblankMode::floating;
 
+      break;
   }
 }
 
@@ -221,6 +225,12 @@ uInt32 FrameManager::scanlines() const
   return myState == State::frame ? myLineInState : myCurrentFrameFinalLines;
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+uInt32 FrameManager::maxVisibleFrameLines() const
+{
+  return myMaxVisibleFrameLines;
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::setTvMode(TvMode mode)
 {
@@ -278,6 +288,13 @@ void FrameManager::setState(FrameManager::State state)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::finalizeFrame(FrameManager::State state)
 {
+  myCurrentFrameFinalLines = myCurrentFrameTotalLines;
+  myCurrentFrameTotalLines = 0;
+  myTotalFrames++;
+
+  if (myTotalFrames > Metrics::initialGarbageFrames)
+    myMaxVisibleFrameLines = std::max(myMaxVisibleFrameLines, myLineInState);
+
   if (myOnFrameComplete) {
     myOnFrameComplete();
   }
@@ -286,12 +303,7 @@ void FrameManager::finalizeFrame(FrameManager::State state)
   (cout << "frame complete @ " << myLineInState << " (" << myCurrentFrameTotalLines << " total)" << "\n").flush();
 #endif // TIA_FRAMEMANAGER_DEBUG_LOG
 
-  myCurrentFrameFinalLines = myCurrentFrameTotalLines;
-  myCurrentFrameTotalLines = 0;
   setState(state);
-
-  myTotalFrames++;
-
   if (myTotalFrames <= Metrics::initialGarbageFrames) {
     return;
   }

src/emucore/tia/FrameManager.hxx

@@ -59,6 +59,8 @@ class FrameManager : public Serializable
 
     uInt32 scanlines() const;
 
+    uInt32 maxVisibleFrameLines() const;
+
     uInt32 frameCount() const { return myTotalFrames; }
 
     float frameRate() const { return myFrameRate; }
@@ -70,6 +72,10 @@ class FrameManager : public Serializable
     bool load(Serializer& in) override;
     string name() const override { return "TIA_FrameManager"; }
 
+  public:
+
+    static constexpr uInt32 frameBufferHeight = 320;
+
   private:
 
     enum State {
@@ -104,6 +110,7 @@ class FrameManager : public Serializable
     uInt32 myLineInState;
     uInt32 myCurrentFrameTotalLines;
     uInt32 myCurrentFrameFinalLines;
+    uInt32 myMaxVisibleFrameLines;
     float  myFrameRate;
 
     uInt32 myTotalFrames;

src/emucore/tia/TIA.cxx

@@ -83,23 +83,15 @@ TIA::TIA(Console& console, Sound& sound, Settings& settings)
 {
   myFrameManager.setHandlers(
     [this] () {
-      myCurrentFrameBuffer.swap(myPreviousFrameBuffer);
-
-      for (uInt8 i = 0; i < 4; i++)
-        updatePaddle(i);
+      onFrameStart();
     },
     [this] () {
-      mySystem->m6502().stop();
-      mySystem->resetCycles();
-
-      // Recalculate framerate, attempting to auto-correct for scanline 'jumps'
-      if(myAutoFrameEnabled)
-        myConsole.setFramerate(myFrameManager.frameRate());
+      onFrameComplete();
     }
   );
 
-  myCurrentFrameBuffer  = make_ptr<uInt8[]>(160 * 320);
-  myPreviousFrameBuffer = make_ptr<uInt8[]>(160 * 320);
+  myCurrentFrameBuffer  = make_ptr<uInt8[]>(160 * FrameManager::frameBufferHeight);
+  myPreviousFrameBuffer = make_ptr<uInt8[]>(160 * FrameManager::frameBufferHeight);
 
   myTIAPinsDriven = mySettings.getBool("tiadriven");
 
@@ -193,8 +185,8 @@ void TIA::installDelegate(System& system, Device& device)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void TIA::clearBuffers()
 {
-  memset(myCurrentFrameBuffer.get(), 0, 160 * 320);
-  memset(myPreviousFrameBuffer.get(), 0, 160 * 320);
+  memset(myCurrentFrameBuffer.get(), 0, 160 * FrameManager::frameBufferHeight);
+  memset(myPreviousFrameBuffer.get(), 0, 160 * FrameManager::frameBufferHeight);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -906,6 +898,31 @@ void TIA::updateEmulation()
   cycle(cyclesToRun);
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void TIA::onFrameStart()
+{
+  myCurrentFrameBuffer.swap(myPreviousFrameBuffer);
+
+  for (uInt8 i = 0; i < 4; i++)
+    updatePaddle(i);
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void TIA::onFrameComplete()
+{
+  mySystem->m6502().stop();
+  mySystem->resetCycles();
+
+  Int32 missingScanlines = myFrameManager.maxVisibleFrameLines() - myFrameManager.currentLine();
+
+  if (missingScanlines > 0)
+    memset(myCurrentFrameBuffer.get() + 160 * myFrameManager.currentLine(), 0, missingScanlines * 160);
+
+  // Recalculate framerate, attempting to auto-correct for scanline 'jumps'
+  if(myAutoFrameEnabled)
+    myConsole.setFramerate(myFrameManager.frameRate());
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void TIA::cycle(uInt32 colorClocks)
 {

src/emucore/tia/TIA.hxx

@@ -351,6 +351,10 @@ class TIA : public Device
 
   private:
 
+    void onFrameStart();
+
+    void onFrameComplete();
+
     void updateEmulation();
 
     void cycle(uInt32 colorClocks);