Fix buggy blanking of line 0.

src/emucore/tia/FrameManager.cxx

@@ -67,11 +67,13 @@ FrameManager::FrameManager()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::setHandlers(
   FrameManager::callback frameStartCallback,
-  FrameManager::callback frameCompleteCallback
+  FrameManager::callback frameCompleteCallback,
+  FrameManager::callback renderingStartCallback
 )
 {
   myOnFrameStart = frameStartCallback;
   myOnFrameComplete = frameCompleteCallback;
+  myOnRenderingStart = renderingStartCallback;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -199,6 +201,7 @@ void FrameManager::setState(FrameManager::State state)
       break;
 
     case State::frame:
+      if (myOnRenderingStart) myOnRenderingStart();
       myVsyncLines = 0;
       myY = 0;
       break;

src/emucore/tia/FrameManager.hxx

@@ -39,7 +39,11 @@ class FrameManager : public Serializable
 
     static uInt8 initialGarbageFrames();
 
-    void setHandlers(callback frameStartCallback, callback frameCompletionCallback);
+    void setHandlers(
+      callback frameStartCallback,
+      callback frameCompletionCallback,
+      callback renderingStartCallback
+    );
 
     void reset();
 
@@ -136,6 +140,7 @@ class FrameManager : public Serializable
 
     callback myOnFrameStart;
     callback myOnFrameComplete;
+    callback myOnRenderingStart;
 
     VblankManager myVblankManager;
 

src/emucore/tia/TIA.cxx

@@ -82,6 +82,9 @@ TIA::TIA(Console& console, Sound& sound, Settings& settings)
     },
     [this] () {
       onFrameComplete();
+    },
+    [this] () {
+      onRenderingStart();
     }
   );
 
@@ -123,6 +126,7 @@ void TIA::reset()
   myLastCycle = 0;
   mySubClock = 0;
   myXDelta = 0;
+  myXAtRenderingStart = 0;
 
   memset(myShadowRegisters, 0, 64);
 
@@ -986,10 +990,7 @@ void TIA::updateEmulation()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void TIA::onFrameStart()
 {
-  const Int32 x = myHctr - 68;
+  myXAtRenderingStart = 0;
-
-  if (x > 0)
-    memset(myFramebuffer.get(), 0, x);
 
   for (uInt8 i = 0; i < 4; i++)
     updatePaddle(i);
@@ -1014,12 +1015,21 @@ void TIA::onFrameStart()
   }
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void TIA::onRenderingStart()
+{
+  myXAtRenderingStart = myHctr > 68 ? myHctr - 68 : 0;
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void TIA::onFrameComplete()
 {
   mySystem->m6502().stop();
   mySystem->resetCycles();
 
+  if (myXAtRenderingStart > 0)
+    memset(myFramebuffer.get(), 0, myXAtRenderingStart);
+
   // Blank out any extra lines not drawn this frame
   const uInt32 missingScanlines = myFrameManager.missingScanlines();
   if (missingScanlines > 0)

src/emucore/tia/TIA.hxx

@@ -396,6 +396,8 @@ class TIA : public Device
 
     void onFrameStart();
 
+    void onRenderingStart();
+
     void onFrameComplete();
 
     void onHalt();
@@ -477,6 +479,7 @@ class TIA : public Device
     Int32 myHblankCtr;
     Int32 myHctr;
     uInt32 myXDelta;
+    uInt32 myXAtRenderingStart;
 
     bool myCollisionUpdateRequired;
     uInt32 myCollisionMask;