Make sure that every frame draws all scanlines in the height of the window.

If the ROM doesn't reach that far, blank out all further scanlines.

Optimize FrameManager::height() method.

src/emucore/tia/FrameManager.cxx

@@ -56,6 +56,7 @@ uInt8 FrameManager::initialGarbageFrames()
 FrameManager::FrameManager()
   : myMode(TvMode::pal),
     myAutodetectTvMode(true),
+    myHeight(0),
     myFixedHeight(0)
 {
   updateTvMode(TvMode::ntsc);
@@ -120,8 +121,11 @@ void FrameManager::nextLine()
       break;
 
     case State::frame:
-      if (myLineInState >= (myFixedHeight > 0 ? myFixedHeight : (myKernelLines + Metrics::visibleOverscan)))
+      if (myLineInState >= myHeight)
+      {
+        myLastY = ystart() + myY;  // Last line drawn in this frame
         setState(State::waitForVsyncStart);
+      }
       break;
 
     default:
@@ -131,6 +135,15 @@ void FrameManager::nextLine()
   if (myState == State::frame && previousState == State::frame) myY++;
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+uInt32 FrameManager::missingScanlines() const
+{
+  if (myLastY == ystart() + myY)
+    return 0;
+  else
+    return myHeight - myY;
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::setVsync(bool vsync)
 {
@@ -278,6 +291,7 @@ void FrameManager::updateTvMode(TvMode mode)
   }
 
   myFrameLines = Metrics::vsync + myVblankLines + myKernelLines + myOverscanLines;
+  setFixedHeight(myFixedHeight);  // update since myKernelLines may have changed
 
   myVblankManager.setVblankLines(myVblankLines);
 }
@@ -294,9 +308,10 @@ void FrameManager::setVblank(bool vblank)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-uInt32 FrameManager::height() const
+void FrameManager::setFixedHeight(uInt32 height)
 {
-  return myFixedHeight > 0 ? myFixedHeight : (myKernelLines + Metrics::visibleOverscan);
+  myFixedHeight = height;
+  myHeight = myFixedHeight > 0 ? myFixedHeight : (myKernelLines + Metrics::visibleOverscan);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/emucore/tia/FrameManager.hxx

@@ -57,9 +57,9 @@ class FrameManager : public Serializable
 
     bool vsync() const { return myVsync; }
 
-    uInt32 height() const;
+    uInt32 height() const { return myHeight; }
 
-    void setFixedHeight(uInt32 height) { myFixedHeight = height; }
+    void setFixedHeight(uInt32 height);
 
     uInt32 getY() const { return myY; }
 
@@ -67,6 +67,8 @@ class FrameManager : public Serializable
 
     uInt32 scanlinesLastFrame() const { return myCurrentFrameFinalLines; }
 
+    uInt32 missingScanlines() const;
+
     uInt32 frameCount() const { return myTotalFrames; }
 
     float frameRate() const { return myFrameRate; }
@@ -135,7 +137,7 @@ class FrameManager : public Serializable
     uInt32 myCurrentFrameFinalLines;
     uInt32 myVsyncLines;
     float  myFrameRate;
-    uInt32 myY;
+    uInt32 myY, myLastY;
     bool myFramePending;
 
     uInt32 myTotalFrames;
@@ -148,6 +150,7 @@ class FrameManager : public Serializable
     uInt32 myKernelLines;
     uInt32 myOverscanLines;
     uInt32 myFrameLines;
+    uInt32 myHeight;
     uInt32 myFixedHeight;
 
   private:

src/emucore/tia/TIA.cxx

@@ -117,7 +117,6 @@ void TIA::reset()
   myLastCycle = 0;
   mySubClock = 0;
   myXDelta = 0;
-  myLastFrameHeight[0] = myLastFrameHeight[1] = 0;
 
   myBackground.reset();
   myPlayfield.reset();
@@ -827,10 +826,6 @@ void TIA::updateEmulation()
 void TIA::swapBuffers()
 {
   myCurrentFrameBuffer.swap(myPreviousFrameBuffer);
-
-  uInt32 tmp = myLastFrameHeight[0];
-  myLastFrameHeight[0] = myLastFrameHeight[1];
-  myLastFrameHeight[1] = tmp;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -853,13 +848,11 @@ void TIA::onFrameComplete()
   mySystem->m6502().stop();
   mySystem->resetCycles();
 
-  const Int32 missingScanlines = myLastFrameHeight[0] - myFrameManager.getY();
-
+  // Blank out any extra lines not drawn this frame
+  const uInt32 missingScanlines = myFrameManager.missingScanlines();
   if (missingScanlines > 0)
     memset(myCurrentFrameBuffer.get() + 160 * myFrameManager.getY(), 0, missingScanlines * 160);
 
-  myLastFrameHeight[0] = myFrameManager.getY();
-
   // Recalculate framerate, attempting to auto-correct for scanline 'jumps'
   if(myAutoFrameEnabled)
     myConsole.setFramerate(myFrameManager.frameRate());

src/emucore/tia/TIA.hxx

@@ -445,7 +445,6 @@ class TIA : public Device
     // Pointer to the current and previous frame buffers
     BytePtr myCurrentFrameBuffer;
     BytePtr myPreviousFrameBuffer;
-    uInt32 myLastFrameHeight[2];
 
     Background myBackground;
     Playfield myPlayfield;