Most of the time we use a GameCommand to store state, we don't want

Apply() itself to load the screen; we want to stuff it in m_sNextScreen
and let the normal screen loading code path do it.  That's why we have
GetAndClearScreen.

However, GetAndClearScreen is a non-const, and applying a GameCommand
should be a const operation.  It doesn't get along well with screen
reuse; once you've applied it, you've destroyed the GameCommand.

Instead, hold a flag indicating whether or not to apply screens, and
set this true on load when we handle it manually.  We should probably
*always* do this, and never load a screen within GameCommand itself, so
this may go away soon (always on).

stepmania/src/GameCommand.cpp

@@ -23,6 +23,7 @@
 
 void GameCommand::Init()
 {
+	m_bApplyCommitsScreens = true;
 	m_sName = "";
 	m_sText = "";
 	m_bInvalid = true;
@@ -591,6 +592,7 @@ void GameCommand::Apply( const vector<PlayerNumber> &vpns ) const
 		{
 			GameCommand gc;
 			gc.m_bInvalid = false;
+			gc.m_bApplyCommitsScreens = m_bApplyCommitsScreens;
 			gc.LoadOne( *cmd );
 			gc.ApplySelf( vpns );
 		}
@@ -669,7 +671,7 @@ void GameCommand::ApplySelf( const vector<PlayerNumber> &vpns ) const
 		}
 		LUA->Release(L);
 	}
-	if( m_sScreen != "" )
+	if( m_sScreen != "" && m_bApplyCommitsScreens )
 		SCREENMAN->SetNewScreen( m_sScreen );
 	if( m_pSong )
 	{

stepmania/src/GameCommand.h

@@ -41,6 +41,10 @@ public:
 	bool IsZero() const;
 	CString GetAndClearScreen();
 	
+	/* If true, Apply() will apply m_sScreen.  If false, it won't, and you need
+	 * to do it yourself. */
+	void ApplyCommitsScreens( bool bOn ) { m_bApplyCommitsScreens = bOn; }
+
 	// Same as what was passed to Load.  We need to keep the original commands
 	// so that we know the order of commands when it comes time to Apply.
 	Commands	m_Commands;
@@ -82,6 +86,9 @@ public:
 
 	// Lua
 	void PushSelf( lua_State *L );
+
+private:
+	bool		m_bApplyCommitsScreens;
 };
 
 #endif