Clear FB before running autodetection.

.vscode/settings.json

@@ -12,5 +12,19 @@
     "editor.trimAutoWhitespace": true,
     "editor.useTabStops": false,
     "C_Cpp.intelliSenseEngine": "Default",
-    "files.insertFinalNewline": true
+    "files.insertFinalNewline": true,
+    "files.associations": {
+        "__split_buffer": "cpp",
+        "__tree": "cpp",
+        "atomic": "cpp",
+        "deque": "cpp",
+        "ios": "cpp",
+        "list": "cpp",
+        "map": "cpp",
+        "set": "cpp",
+        "string": "cpp",
+        "string_view": "cpp",
+        "system_error": "cpp",
+        "vector": "cpp"
+    }
 }

src/common/FrameBufferSDL2.cxx

@@ -298,3 +298,10 @@ void FrameBufferSDL2::readPixels(uInt8* pixels, uInt32 pitch,
 
   SDL_RenderReadPixels(myRenderer, &r, 0, pixels, pitch);
 }
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void FrameBufferSDL2::clear()
+{
+  invalidate();
+  postFrameUpdate();
+}

src/common/FrameBufferSDL2.hxx

@@ -95,6 +95,11 @@ class FrameBufferSDL2 : public FrameBuffer
     */
     void readPixels(uInt8* buffer, uInt32 pitch, const GUI::Rect& rect) const override;
 
+    /**
+      Clear the frame buffer
+    */
+    void clear() override;
+
   protected:
     //////////////////////////////////////////////////////////////////////
     // The following are derived from protected methods in FrameBuffer.hxx

src/emucore/Console.cxx

@@ -117,8 +117,9 @@ Console::Console(OSystem& osystem, unique_ptr<Cartridge>& cart,
   const string& md5 = myProperties.get(Cartridge_MD5);
   setControllers(md5);
 
-  // Mute audio while autodetection runs
+  // Mute audio and clear framebuffer while autodetection runs
   myOSystem.sound().mute(1);
+  myOSystem.frameBuffer().clear();
 
   if(myDisplayFormat == "AUTO" || myOSystem.settings().getBool("rominfo"))
   {

src/emucore/FrameBuffer.hxx

@@ -304,6 +304,11 @@ class FrameBuffer
     */
     virtual void readPixels(uInt8* buffer, uInt32 pitch, const GUI::Rect& rect) const = 0;
 
+    /**
+      Clear the framebuffer.
+    */
+    virtual void clear() = 0;
+
   protected:
     /**
       This method is called to query and initialize the video hardware