Frame manager fixes

* Don't wait until next line before starting frame after vblank is
      deactivated -> fixes white line on top of time pilot
    * Make ystart match stella 4 conventions

src/emucore/tia/FrameManager.cxx

@@ -297,7 +297,12 @@ uInt32 FrameManager::ystart() const
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::setVblank(bool vblank)
 {
-  myVblankManager.setVblank(vblank);
+  if (myState == State::waitForFrameStart) {
+    if (myVblankManager.setVblankDuringVblank(vblank, myTotalFrames <= Metrics::initialGarbageFrames)) {
+      setState(State::frame);
+    }
+  } else
+    myVblankManager.setVblank(vblank);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/emucore/tia/TIA.cxx

@@ -835,6 +835,11 @@ void TIA::onFrameStart()
 {
   swapBuffers();
 
+  const Int32 x = myHctr - 68;
+
+  if (x > 0)
+    memset(myCurrentFrameBuffer.get() + 160 * myFrameManager.getY(), 0, x);
+
   for (uInt8 i = 0; i < 4; i++)
     updatePaddle(i);
 }
@@ -845,7 +850,7 @@ void TIA::onFrameComplete()
   mySystem->m6502().stop();
   mySystem->resetCycles();
 
-  Int32 missingScanlines = myLastFrameHeight[0] - myFrameManager.getY();
+  const Int32 missingScanlines = myLastFrameHeight[0] - myFrameManager.getY();
 
   if (missingScanlines > 0)
     memset(myCurrentFrameBuffer.get() + 160 * myFrameManager.getY(), 0, missingScanlines * 160);

src/emucore/tia/VblankManager.cxx

@@ -44,6 +44,7 @@ void VblankManager::reset()
   myStableVblankFrames = 0;
   myVblankViolated = false;
   myLastVblankLines = 0;
+  myIsRunning = false;
 
   if (myMode != VblankMode::fixed) myMode = VblankMode::floating;
 }
@@ -52,13 +53,63 @@ void VblankManager::reset()
 void VblankManager::start()
 {
   myCurrentLine = 0;
+  myIsRunning = true;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 bool VblankManager::nextLine(bool isGarbageFrame)
 {
+  if (!myIsRunning) return false;
+
   myCurrentLine++;
 
+  const bool transition =
+    myMode == VblankMode::fixed ? (myCurrentLine >= myYstart) : shouldTransition(isGarbageFrame);
+
+  if (transition) myIsRunning = false;
+
+  return transition;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void VblankManager::setVblankLines(uInt32 vblankLines)
+{
+  myVblankLines = vblankLines;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void VblankManager::setYstart(uInt32 ystart)
+{
+  if (ystart == myYstart) return;
+
+  myYstart = ystart;
+
+  myMode = ystart ? VblankMode::fixed : VblankMode::floating;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void VblankManager::setVblank(bool vblank)
+{
+  myVblank = vblank;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+bool VblankManager::setVblankDuringVblank(bool vblank, bool isGarbageFrame)
+{
+  const bool oldVblank = myVblank;
+
+  myVblank = vblank;
+  if (!myIsRunning || vblank || oldVblank == myVblank) return false;
+
+  const bool transition = shouldTransition(isGarbageFrame);
+  if (transition) myIsRunning = false;
+
+  return transition;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+bool VblankManager::shouldTransition(bool isGarbageFrame)
+{
   bool shouldTransition = myCurrentLine >= (myVblank ? myVblankLines : myVblankLines - Metrics::maxUnderscan);
   bool transition = false;
 
@@ -114,42 +165,14 @@ bool VblankManager::nextLine(bool isGarbageFrame)
 
       break;
 
-    case VblankMode::fixed:
-      if (myCurrentLine > myYstart) transition = true;
+    default:
+      transition = false;
       break;
-
   }
 
   return transition;
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void VblankManager::setVblankLines(uInt32 vblankLines)
-{
-  myVblankLines = vblankLines;
-}
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void VblankManager::setYstart(uInt32 ystart)
-{
-  if (ystart == myYstart) return;
-
-  myYstart = ystart;
-
-  myMode = ystart ? VblankMode::fixed : VblankMode::floating;
-}
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void VblankManager::setVblank(bool vblank)
-{
-#ifdef TIA_VBLANK_MANAGER_DEBUG_LOG
-  if (myVblank != vblank)
-    (cout << "vblank " << myVblank << " -> " << vblank << ": state " << int(myState) << " @ " << myLineInState << "\n").flush();
-#endif
-
-  myVblank = vblank;
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 // TODO: implement this once the class is finalized
 bool VblankManager::save(Serializer& out) const

src/emucore/tia/VblankManager.hxx

@@ -42,6 +42,8 @@ class VblankManager : public Serializable
 
     void setVblank(bool vblank);
 
+    bool setVblankDuringVblank(bool vblank, bool isGarbageFrame);
+
     bool vblank() const { return myVblank; }
 
     uInt32 currentLine() const {return myCurrentLine; };
@@ -61,6 +63,10 @@ class VblankManager : public Serializable
       fixed
     };
 
+  private:
+
+    bool shouldTransition(bool isGarbageFrame);
+
   private:
 
     uInt32 myVblankLines;
@@ -75,6 +81,8 @@ class VblankManager : public Serializable
     uInt8 myStableVblankFrames;
     bool myVblankViolated;
 
+    bool myIsRunning;
+
   private:
 
     VblankManager(const VblankManager&) = delete;