Bug fixing spree -> scanline count works as expected.

src/emucore/Console.hxx

@@ -311,6 +311,12 @@ class Console : public Serializable, public ConsoleIO
      */
     void updateVcenter(Int32 vcenter);
 
+    /**
+      Set up various properties of the TIA (vcenter, Height, etc) based on
+      the current display format.
+    */
+    void setTIAProperties();
+
   private:
     /**
      * Dry-run the emulation and detect the frame layout (PAL / NTSC).
@@ -322,12 +328,6 @@ class Console : public Serializable, public ConsoleIO
      */
     void redetectFrameLayout();
 
-    /**
-      Sets various properties of the TIA (vcenter, Height, etc) based on
-      the current display format.
-    */
-    void setTIAProperties();
-
     /**
       Create the audio queue
      */

src/emucore/tia/frame-manager/FrameManager.cxx

@@ -220,8 +220,8 @@ bool FrameManager::onLoad(Serializer& in)
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::recalculateMetrics() {
-  uInt32 ystartBase;
-  uInt32 baseHeight;
+  Int32 ystartBase;
+  Int32 baseHeight;
 
   switch (layout())
   {
@@ -244,7 +244,7 @@ void FrameManager::recalculateMetrics() {
   }
 
   myHeight = baseHeight + myAdjustScanlines * 2;
-  myYStart = ystartBase + baseHeight - myHeight + myVcenter;
+  myYStart = std::max(0, ystartBase + (baseHeight - static_cast<Int32>(myHeight)) / 2 + myVcenter);
 
   myJitterEmulation.setYStart(myYStart);
 }

src/gui/VideoDialog.cxx

@@ -487,6 +487,8 @@ void VideoDialog::saveConfig()
   // TV scanline intensity
   instance().settings().setValue("tv.scanlines", myTVScanIntense->getValueLabel());
 
+  instance().console().setTIAProperties();
+
   // Finally, issue a complete framebuffer re-initialization...
   instance().createFrameBuffer();