allow overlay layers to grab focus

stepmania/src/ScreenManager.cpp

@@ -54,6 +54,7 @@ void ScreenManager::Register( const CString& sClassName, CreateScreenFn pfn )
 ScreenManager::ScreenManager()
 {
 	m_pSharedBGA = new Actor;
+	m_pInputFocus = NULL;
 
 	m_MessageSendOnPop = SM_None;
 
@@ -239,8 +240,12 @@ void ScreenManager::Input( const DeviceInput& DeviceI, const InputEventType type
 //		DeviceI.device, DeviceI.button, GameI.controller, GameI.button, MenuI.player, MenuI.button, StyleI.player, StyleI.col );
 
 	// pass input only to topmost state
-	if( !m_ScreenStack.empty() )
-		m_ScreenStack.back()->Input( DeviceI, type, GameI, MenuI, StyleI );
+	Screen *pInputFocus = m_pInputFocus;
+	if( pInputFocus == NULL && !m_ScreenStack.empty() )
+		pInputFocus = m_ScreenStack.back();
+
+	if( pInputFocus != NULL )
+		pInputFocus->Input( DeviceI, type, GameI, MenuI, StyleI );
 }
 
 /* Just create a new screen; don't do any associated cleanup. */
@@ -551,11 +556,31 @@ void ScreenManager::SystemMessageNoAnimate( const CString &sMessage )
 	MESSAGEMAN->Broadcast( "SystemMessageNoAnimate" );
 }
 
-CString ScreenManager::GetCurrentSystemMessage() const
+bool ScreenManager::GrabInputFocus( const Screen *pScreen )
 {
-	return m_sSystemMessage;
+	if( m_pInputFocus != NULL )
+		return false;
+
+	/* Sanity check: make sure that the screen is in m_OverlayScreens. */
+	for( unsigned i = 0; i < m_OverlayScreens.size(); ++i )
+	{
+		if( m_OverlayScreens[i] == pScreen )
+		{
+			m_pInputFocus = m_OverlayScreens[i];
+			return true;
+		}
+	}
+
+	FAIL_M( "GrabInputFocus: unknown screen" );
 }
 
+void ScreenManager::ReleaseInputFocus( const Screen *pScreen )
+{
+	ASSERT( m_pInputFocus == pScreen );
+	m_pInputFocus = NULL;
+}
+
+
 void ScreenManager::RefreshCreditsMessages()
 {
 	MESSAGEMAN->Broadcast( "RefreshCreditText" );