Validate changes to edit descriptions. Ignore attempts to clear

descriptions for edits (that'd be like renaming a file to not
have a filename).

stepmania/src/ScreenEdit.cpp

@@ -2435,9 +2435,44 @@ void ScreenEdit::OnSnapModeChange()
 static void ChangeDescription( const CString &sNew )
 {
 	Steps* pSteps = GAMESTATE->m_pCurSteps[PLAYER_1];
+
+	/* Don't erase edit descriptions. */
+	if( sNew.empty() && pSteps->GetDifficulty() == DIFFICULTY_EDIT )
+		return;
+
 	pSteps->SetDescription(sNew);
 }
 
+static bool ValidateDescription( const CString &sAnswer, CString &sErrorOut )
+{
+	if( sAnswer.empty() )
+		return true;
+
+	/* Don't allow duplicate edit names within the same StepsType; edit names uniquely
+	 * identify the edit. */
+	Steps *pSteps = GAMESTATE->m_pCurSteps[PLAYER_1];
+	Song *pSong = GAMESTATE->m_pCurSong;
+	if( pSteps->GetDifficulty() != DIFFICULTY_EDIT )
+		return true;
+
+	/* If unchanged: */
+	if( pSteps->GetDescription() == sAnswer )
+		return true;
+
+	vector<Steps*> apSteps;
+	pSong->GetSteps( apSteps, pSteps->m_StepsType, DIFFICULTY_EDIT, -1, -1, sAnswer );
+
+	if( apSteps.size() == 0 )
+		return true;
+
+	/* The name is already used, */
+	if( apSteps.size() > 1 )
+		LOG->Warn( "Multiple edits for song \"%s\" named \"%s\"", pSong->GetSongDir().c_str(), sAnswer.c_str() );
+
+	sErrorOut = "The supplied name supplied conflicts with another edit.\n\nPlease use a different name.";
+	return false;
+}
+
 static void ChangeMainTitle( const CString &sNew )
 {
 	Song* pSong = GAMESTATE->m_pCurSong;
@@ -3031,7 +3066,7 @@ void ScreenEdit::HandleStepsInformationChoice( StepsInformationChoice c, const v
 			ENTER_NEW_DESCRIPTION, 
 			m_pSteps->GetDescription(), 
 			(dc == DIFFICULTY_EDIT) ? MAX_EDIT_STEPS_DESCRIPTION_LENGTH : 255,
-			NULL,
+			ValidateDescription,
 			ChangeDescription, 
 			NULL 
 			);