reverse and limit vcenter

src/common/PKeyboardHandler.cxx

@@ -426,8 +426,8 @@ PhysicalKeyboardHandler::EventMappingArray PhysicalKeyboardHandler::DefaultCommo
 
   {Event::VidmodeDecrease,          KBDK_MINUS, MOD3},
   {Event::VidmodeIncrease,          KBDK_EQUALS, MOD3},
-  {Event::VCenterDecrease,          KBDK_PAGEDOWN, MOD3},
+  {Event::VCenterDecrease,          KBDK_PAGEUP, MOD3},
-  {Event::VCenterIncrease,          KBDK_PAGEUP, MOD3},
+  {Event::VCenterIncrease,          KBDK_PAGEDOWN, MOD3},
   {Event::ScanlineAdjustDecrease,   KBDK_PAGEDOWN, KBDM_SHIFT | MOD3},
   {Event::ScanlineAdjustIncrease,   KBDK_PAGEUP, KBDM_SHIFT | MOD3},
   {Event::VolumeDecrease,           KBDK_LEFTBRACKET, MOD3},

src/emucore/Console.cxx

@@ -642,22 +642,20 @@ void Console::changeVerticalCenter(int direction)
 
   if(direction == +1)       // increase vcenter
   {
-    if(vcenter >= TIAConstants::maxVcenter)
+    if(vcenter >= myTIA->maxVcenter())
-    {
-      myOSystem.frameBuffer().showMessage("V-Center at minimum");
-      return;
-    }
-
-    ++vcenter;
-  }
-  else if(direction == -1)  // decrease vcenter
-  {
-    if (vcenter <= TIAConstants::minVcenter)
     {
       myOSystem.frameBuffer().showMessage("V-Center at maximum");
       return;
     }
-
+    ++vcenter;
+  }
+  else if(direction == -1)  // decrease vcenter
+  {
+    if (vcenter <= myTIA->minVcenter())
+    {
+      myOSystem.frameBuffer().showMessage("V-Center at minimum");
+      return;
+    }
     --vcenter;
   }
   else

src/emucore/tia/TIA.hxx

@@ -252,6 +252,8 @@ class TIA : public Device
     uInt32 width() const  { return TIAConstants::H_PIXEL; }
     uInt32 height() const { return myFrameManager->height(); }
     Int32 vcenter() const { return myFrameManager->vcenter(); }
+    Int32 minVcenter() const { return myFrameManager->minVcenter(); }
+    Int32 maxVcenter() const { return myFrameManager->maxVcenter(); }
     uInt32 startLine() const { return myFrameManager->startLine(); }
 
     /**

src/emucore/tia/TIAConstants.hxx

@@ -24,8 +24,8 @@ namespace TIAConstants {
 
   static constexpr uInt32 frameBufferWidth = 160;
   static constexpr uInt32 frameBufferHeight = 320;
-  static constexpr Int32 maxVcenter = 20; // limit to reasonable values
   static constexpr Int32 minVcenter = -20; // limit to reasonable values
+  static constexpr Int32 maxVcenter = 20; // limit to reasonable values
   static constexpr uInt32 viewableWidth = 320;
   static constexpr uInt32 viewableHeight = 240;
   static constexpr uInt32 initialGarbageFrames = 10;

src/emucore/tia/frame-manager/AbstractFrameManager.hxx

@@ -170,6 +170,17 @@ class AbstractFrameManager : public Serializable
      */
     virtual Int32 vcenter() const { return 0; }
 
+    /**
+     * The calculated minimal vcenter value.
+     */
+    virtual Int32 minVcenter() const { return 0; }
+
+    /**
+     * The calculated maximal vcenter value.
+     */
+    virtual Int32 maxVcenter() const { return 0; }
+
+
     virtual void setAdjustScanlines(Int32 adjustScanlines) {}
 
     virtual Int32 adjustScanlines() const { return 0; }

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

@@ -244,7 +244,9 @@ void FrameManager::recalculateMetrics() {
   }
 
   myHeight = BSPF::clamp<uInt32>(baseHeight + myAdjustScanlines * 2, 0, myFrameLines);
-  myYStart = BSPF::clamp<uInt32>(ystartBase + (baseHeight - static_cast<Int32>(myHeight)) / 2 + myVcenter, 0, myFrameLines);
+  myYStart = BSPF::clamp<uInt32>(ystartBase + (baseHeight - static_cast<Int32>(myHeight)) / 2 - myVcenter, 0, myFrameLines);
+  // TODO: why "- 1" here: ???
+  myMaxVcenter = BSPF::clamp<Int32>(ystartBase + (baseHeight - static_cast<Int32>(myHeight)) / 2 - 1, 0, TIAConstants::maxVcenter);
 
   myJitterEmulation.setYStart(myYStart);
 }

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

@@ -48,6 +48,10 @@ class FrameManager: public AbstractFrameManager {
 
     Int32 vcenter() const override { return myVcenter; }
 
+    Int32 minVcenter() const override { return TIAConstants::minVcenter; }
+
+    Int32 maxVcenter() const override { return myMaxVcenter; }
+
     void setAdjustScanlines(Int32 adjustScanlines) override;
 
     Int32 adjustScanlines() const override { return myAdjustScanlines; }
@@ -97,6 +101,7 @@ class FrameManager: public AbstractFrameManager {
     uInt32 myHeight{0};
     uInt32 myYStart{0};
     Int32 myVcenter{0};
+    Int32 myMaxVcenter{0};
     Int32 myAdjustScanlines{0};
 
     bool myJitterEnabled{false};