Add explicit API to copy Locations

This is in preparation to reduce signals during
Location Drag motion (which operates on a copied
Location, that causes [static] signal emissions,
but the location itself is not in any list).

libs/ardour/ardour/location.h

@@ -73,7 +73,7 @@ public:
 
 	Location (Session &);
 	Location (Session &, Temporal::timepos_t const &, Temporal::timepos_t const &, const std::string &, Flags bits = Flags(0), int32_t cue_id = 0);
-	Location (const Location& other);
+	Location (Location const& other, bool no_signal);
 	Location (Session &, const XMLNode&);
 	Location* operator= (const Location& other);
 
@@ -207,6 +207,7 @@ protected:
 	void resume_signals ();
 
 private:
+	Location (Location const&); // no copy c'tor
 	void set_mark (bool yn);
 	bool set_flag_internal (bool yn, Flags flag);
 

libs/ardour/location.cc

@@ -91,7 +91,7 @@ Location::Location (Session& s, timepos_t const & start, timepos_t const & end,
 	set_position_time_domain (_session.time_domain());
 }
 
-Location::Location (const Location& other)
+Location::Location (const Location& other, bool no_emit)
 	: SessionHandleRef (other._session)
 	, _name (other._name)
 	, _start (other._start)
@@ -101,8 +101,13 @@ Location::Location (const Location& other)
 	, _cue (other._cue)
 	, _signals_suspended (0)
 {
-	/* copy is not locked even if original was */
-	assert (other._signals_suspended == 0);
+	if (no_emit) {
+		/* use for temp. copies (e.g. during Drag) */
+		suspend_signals ();
+	} else {
+		/* copy is not locked even if original was */
+		assert (other._signals_suspended == 0);
+	}
 
 	_locked = false;
 
@@ -1934,7 +1939,7 @@ Locations::cut_copy_section (timepos_t const& start, timepos_t const& end, timep
 
 		} else if (op == CopyPasteSection) {
 			if (i->start() >= start && i->start() < end) {
-				Location* copy = new Location (*i);
+				Location* copy = new Location (*i, false);
 				pastebuf.push_back (copy);
 			}
 		}

libs/ardour/location_importer.cc

@@ -135,7 +135,7 @@ LocationImporter::_prepare_move ()
 {
 	try {
 		Location const original (session, xml_location);
-		location = new Location (original); // Updates id
+		location = new Location (original, false); // Updates id
 	} catch (failed_constructor& err) {
 		throw std::runtime_error (X_("Error in session file!"));
 		return false;