X-Git-Url: http://git.tdb.fi/?p=libs%2Fdatafile.git;a=blobdiff_plain;f=source%2Fcollection.h;h=0d2dc6be2fd7a6c4043ff4db18bfdc32a04bb270;hp=bbde9f904dfd3e8415ae0e0a8dc0ae8b2d9db641;hb=9b1656018f783eb4aad2fbdc1de1404691e89bb1;hpb=af043eaec121bbd6f5e3ad36059c281f1b20bf8f

diff --git a/source/collection.h b/source/collection.h
index bbde9f9..0d2dc6b 100644
--- a/source/collection.h
+++ b/source/collection.h
@@ -45,6 +45,11 @@ method for details.
 
 Collections can have sources for loading objects on demand.  Automatic loading
 only works on a non-const Collection.  See class CollectionSource for details.
+
+A fallback collection can be designated as another way of loading items that
+are not present.  Items retrieted from the fallback collection are shared
+between the collections, and are only deleted when all collections in the chain
+have been destroyed.
 */
 class Collection
 {
@@ -86,11 +91,12 @@ private:
 	TypeList types;
 	ItemMap items;
 	SourceList sources;
+	Collection *fallback;
 
 	Collection(const Collection &);
 	Collection &operator=(const Collection &);
 public:
-	Collection() { }
+	Collection();
 	virtual ~Collection();
 
 	/** Adds an object into the collection.  The name must not pre-exist.  The
@@ -258,10 +264,17 @@ private:
 protected:
 	void add_source(CollectionSource &);
 
+	IO::Seekable *open_from_sources(const std::string &);
+
 private:
 	void gather_names_from_sources(std::list<std::string> &, const CollectionItemTypeBase &) const;
 
 	void load_items_from_sources(const CollectionItemTypeBase &);
+
+protected:
+	/** Sets a fallback collection, which will be consulted if an item is not
+	found. */
+	void set_fallback(Collection *);
 };
 
 template<typename T>
@@ -309,6 +322,7 @@ public:
 	const std::string &get_keyword() const { return kwd; }
 	void add_suffix(const std::string &);
 	bool match_name(const std::string &) const;
+	virtual bool is_same_type(const CollectionItemTypeBase &) const = 0;
 	virtual bool check_item_type(const Variant &) const = 0;
 	virtual void add_to_loader(Collection::Loader &) const = 0;
 	virtual bool can_create() const = 0;
@@ -423,6 +437,9 @@ public:
 		return *this;
 	}
 
+	virtual bool is_same_type(const CollectionItemTypeBase &other) const
+	{ return dynamic_cast<const CollectionItemType<T> *>(&other); }
+
 	virtual bool check_item_type(const Variant &var) const
 	{ return var.check_type<RefPtr<T> >(); }