fix PlayMode change message being broadcast multiple times if 2 players joined

stepmania/src/ScreenSelect.cpp

@@ -174,6 +174,34 @@ void ScreenSelect::Input( const DeviceInput& DeviceI, const InputEventType type,
 void ScreenSelect::HandleScreenMessage( const ScreenMessage SM )
 {
 	if( SM == SM_BeginFadingOut )	/* Screen is starting to tween out. */
+	{
+		/*
+		 * Don't call GameCommand::Apply once per player on screens that 
+		 * have a shared selection.  This can cause change messages to be broadcast
+		 * multiple times.  Detect whether all players have the same choice, and 
+		 * if so, call ApplyToAll instead.
+		 * TODO: Think of a better way to handle this.
+		 */
+		int iMastersIndex = this->GetSelectionIndex( GAMESTATE->m_MasterPlayerNumber );
+		bool bAllPlayersChoseTheSame = true;
+		FOREACH_HumanPlayer( p )
+		{
+			if( this->GetSelectionIndex(p) != iMastersIndex )
+			{
+				bAllPlayersChoseTheSame = false;
+				break;
+			}
+		}
+
+		if( bAllPlayersChoseTheSame )
+		{
+			GameCommand &gc = m_aGameCommands[iMastersIndex];
+			CString sThisScreen = gc.GetAndClearScreen();
+			if( m_sNextScreen == "" )
+				m_sNextScreen = sThisScreen;
+			gc.ApplyToAllPlayers();
+		}
+		else
 		{
 			FOREACH_HumanPlayer( p )
 			{
@@ -184,6 +212,8 @@ void ScreenSelect::HandleScreenMessage( const ScreenMessage SM )
 					m_sNextScreen = sThisScreen;
 				gc.Apply( p );
 			}
+		}
+
 
 		SCREENMAN->RefreshCreditsMessages();