add GetSongPercent

stepmania/src/GameState.cpp

@@ -240,6 +240,12 @@ void GameState::UpdateSongPosition(float fPositionSeconds)
 //	LOG->Trace( "m_fMusicSeconds = %f, m_fSongBeat = %f, m_fCurBPS = %f, m_bFreeze = %f", m_fMusicSeconds, m_fSongBeat, m_fCurBPS, m_bFreeze );
 }
 
+float GameState::GetSongPercent( float beat ) const
+{
+	/* 0 = first step; 1 = last step */
+	return (beat - m_pCurSong->m_fFirstBeat) / m_pCurSong->m_fLastBeat;
+}
+
 int GameState::GetStageIndex()
 {
 	return m_iCurrentStageIndex;

stepmania/src/GameState.h

@@ -157,6 +157,7 @@ public:
 
 	void ResetMusicStatistics();	// Call this when it's time to play a new song.  Clears the values above.
 	void UpdateSongPosition(float fPositionSeconds);
+	float GetSongPercent( float beat ) const;
 
 	//
 	// Stage Statistics: