- Split between abstract base class (sgpem::CairoWidget) and

derived widget
- Add History::set_notify_enabled() for usage by the frontend 
(for example, when loading from file, you'll want to call
set_notify_enabled(false) before starting)


git-svn-id: svn://svn.gna.org/svn/sgpemv2/trunk@823 3ecf2c5c-341e-0410-92b4-d18e462d057c

src/backend/history.cc

@@ -28,6 +28,13 @@
 using namespace sgpem;
 using namespace std;
 
+
+History::History()
+  : _notify(true)
+{
+}
+
+
 History::~History()
 {
 }
@@ -52,7 +59,18 @@ History::detach(const HistoryObserver& observer)
 void 
 History::notify_change()
 {
+  if(!_notify) return;
+
 	for(RegisteredObservers::iterator it =_observers.begin(); 
 			it != _observers.end(); it++)
 		(*it)->update(*this);
 }
+
+
+bool
+History::set_notify_enabled(bool enabled)
+{
+  bool r = _notify;
+  _notify = enabled;
+  return r;
+}

src/backend/history.hh

@@ -64,6 +64,7 @@ namespace sgpem
 		typedef Environment::resource_key_t      resource_key_t;
 		typedef const std::pair<resource_key_t, Resource*>  ResourcePair;
 
+    History();
   	virtual ~History() = 0;
 		
 		virtual       size_t       get_size() const = 0;
@@ -102,13 +103,26 @@ namespace sgpem
 
 		virtual void  attach(HistoryObserver& observer);
 		virtual void  detach(const HistoryObserver& observer);
+
+    /** \brief Enable/disable notifications to registered observers
+     *
+     * This is quite useful to disable momentarily notification while you
+     * do a bunch of insertions and/or deletions in one go, in order to 
+     * speed up things.
+     *
+     * \return The old value
+     */
+    virtual bool  set_notify_enabled(bool enabled = true);
 		
 	protected:
 		typedef std::vector<HistoryObserver*> RegisteredObservers;
 		RegisteredObservers _observers;
 
 		virtual void notify_change();
-				
+
+  private:
+    bool _notify;
+
   }; //~ class History
 
 }//~ namespace sgpem