background assert -> warning. This fired, but I can't repro it and the assert didn't give useful data.

stepmania/src/Background.cpp

@@ -23,6 +23,7 @@
 #include "XmlFile.h"
 #include "BackgroundUtil.h"
 #include "song.h"
+#include "RageFileDriverMemory.h"
 
 ThemeMetric<float> LEFT_EDGE					("Background","LeftEdge");
 ThemeMetric<float> TOP_EDGE						("Background","TopEdge");
@@ -250,9 +251,7 @@ void BackgroundImpl::Unload()
 
 void BackgroundImpl::Layer::Unload()
 {
-    for( map<BackgroundDef,Actor*>::iterator iter = m_BGAnimations.begin();
+    FOREACHM( BackgroundDef, Actor*, m_BGAnimations, iter )
-		 iter != m_BGAnimations.end();
-		 iter++ )
 		delete iter->second;
 	m_BGAnimations.clear();
 	m_aBGChanges.clear();
@@ -766,7 +765,16 @@ void BackgroundImpl::Layer::UpdateCurBGChange( const Song *pSong, float fLastMus
 		m_pFadingBGA = m_pCurrentBGA;
 
 		map<BackgroundDef,Actor*>::const_iterator iter = m_BGAnimations.find( change.m_def );
-		ASSERT( iter != m_BGAnimations.end() );
+		if( iter == m_BGAnimations.end() )
+		{
+			XNode *pNode = change.m_def.CreateNode();
+			RageFileObjMem f;
+			pNode->GetXML( f, NULL );
+			LOG->Warn( "Tried to switch to a background that was never loaded\n" + f.GetString() );
+			SAFE_DELETE( pNode );
+			return;
+		}
+
 		m_pCurrentBGA = iter->second;
 
 		if( m_pFadingBGA == m_pCurrentBGA )

stepmania/src/BackgroundUtil.cpp

@@ -7,6 +7,48 @@
 #include "RageLog.h"
 #include <set>
 
+
+bool BackgroundDef::operator<( const BackgroundDef &other ) const
+{
+#define COMPARE(x) if( x < other.x ) return true; else if( x > other.x ) return false;
+	COMPARE( m_sEffect );
+	COMPARE( m_sFile1 );
+	COMPARE( m_sFile2 );
+	COMPARE( m_sColor1 );
+	COMPARE( m_sColor2 );
+#undef COMPARE
+	return false;
+}
+
+bool BackgroundDef::operator==( const BackgroundDef &other ) const
+{
+	return 
+		m_sEffect == other.m_sEffect &&
+		m_sFile1 == other.m_sFile1 &&
+		m_sFile2 == other.m_sFile2 &&
+		m_sColor1 == other.m_sColor1 &&
+		m_sColor2 == other.m_sColor2;
+}
+
+XNode *BackgroundDef::CreateNode() const
+{
+	XNode* pNode = new XNode;
+	pNode->m_sName = "BackgroundDef";
+
+	if( !m_sEffect.empty() )
+		pNode->AppendAttr( "Effect", m_sEffect );
+	if( !m_sFile1.empty() )
+		pNode->AppendAttr( "File1", m_sFile1 );
+	if( !m_sFile2.empty() )
+		pNode->AppendAttr( "File2", m_sFile2 );
+	if( !m_sColor1.empty() )
+		pNode->AppendAttr( "Color1", m_sColor1 );
+	if( !m_sColor2.empty() )
+		pNode->AppendAttr( "Color2", m_sColor2 );
+
+	return pNode;
+}
+
 const CString BACKGROUND_EFFECTS_DIR =		"BackgroundEffects/";
 const CString BACKGROUND_TRANSITIONS_DIR =	"BackgroundTransitions/";
 const CString BG_ANIMS_DIR			= "BGAnimations/";

stepmania/src/BackgroundUtil.h

@@ -4,6 +4,7 @@
 #define BackgroundUtil_H
 
 class Song;
+struct XNode;
 
 extern const CString RANDOM_BACKGROUND_FILE;
 extern const CString NO_SONG_BG_FILE;
@@ -18,35 +19,16 @@ extern const CString SBT_CrossFade;
 
 struct BackgroundDef
 {
-	BackgroundDef()
+	bool operator<( const BackgroundDef &other ) const;
-	{
+	bool operator==( const BackgroundDef &other ) const;
-	}
+	bool IsEmpty() const { return m_sFile1.empty() && m_sFile2.empty(); }
-	bool operator<( const BackgroundDef &other ) const
-	{
-#define COMPARE(x) if( x < other.x ) return true; else if( x > other.x ) return false;
-		COMPARE( m_sEffect );
-		COMPARE( m_sFile1 );
-		COMPARE( m_sFile2 );
-		COMPARE( m_sColor1 );
-		COMPARE( m_sColor2 );
-#undef COMPARE
-		return false;
-	}
-	bool operator==( const BackgroundDef &other ) const
-	{
-		return 
-			m_sEffect == other.m_sEffect &&
-			m_sFile1 == other.m_sFile1 &&
-			m_sFile2 == other.m_sFile2 &&
-			m_sColor1 == other.m_sColor1 &&
-			m_sColor2 == other.m_sColor2;
-	}
-	bool IsEmpty() { return m_sFile1.empty() && m_sFile2.empty(); }
 	CString	m_sEffect;	// "" == automatically choose
 	CString m_sFile1;	// must not be ""
 	CString m_sFile2;	// may be ""
 	CString m_sColor1;	// "" == use default
 	CString m_sColor2;	// "" == use default
+
+	XNode *CreateNode() const;
 };
 
 struct BackgroundChange

stepmania/src/XmlFile.cpp

@@ -515,7 +515,7 @@ char* XNode::Load( const char* pszXml, PARSEINFO *pi /*= &piDefault*/ )
 //========================================================
 bool XAttr::GetXML( RageFileBasic &f, DISP_OPT *opt ) const
 {
-	return f.Write(m_sName + "='" + (opt->reference_value&&opt->entitys?opt->entitys->Entity2Ref(m_sValue):m_sValue) + "' ") != -1;
+	return f.Write(m_sName + "='" + (opt && opt->reference_value && opt->entitys ? opt->entitys->Entity2Ref(m_sValue) : m_sValue) + "' ") != -1;
 }
 
 //========================================================