Fix for visual glitch due to race between Editor::update_current_screen being called and a locate event being processed.

git-svn-id: svn://localhost/ardour2/branches/3.0@4608 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/editor.cc

@@ -248,7 +248,8 @@ Editor::Editor ()
 	  /* nudge */
 
 	  nudge_clock (X_("nudge"), false, X_("NudgeClock"), true, true),
-	  meters_running(false)
+	  meters_running(false),
+	  _pending_locate_request (false)
 
 {
 	constructed = false;
@@ -1280,6 +1281,8 @@ Editor::connect_to_session (Session *t)
 
 	session_connections.push_back (session->tempo_map().StateChanged.connect (mem_fun(*this, &Editor::tempo_map_changed)));
 
+	session_connections.push_back (session->Located.connect (mem_fun (*this, &Editor::located)));
+
 	edit_groups_changed ();
 
 	edit_point_clock.set_mode(AudioClock::BBT);
@@ -5346,3 +5349,11 @@ Editor::idle_resize ()
 	resize_idle_id = -1;
 	return false;
 }
+
+void
+Editor::located ()
+{
+	ENSURE_GUI_THREAD (mem_fun (*this, &Editor::located));
+
+	_pending_locate_request = false;
+}

gtk2_ardour/editor.h

@@ -2376,6 +2376,9 @@ public:
 
 	void visible_order_range (int*, int*) const;
 	bool y_movement_disallowed (int, int, int, int, int, std::bitset<512> const &, std::vector<int32_t> const &) const;
+
+	void located ();
+	bool _pending_locate_request;
 };
 
 #endif /* __ardour_editor_h__ */

gtk2_ardour/editor_mixer.cc

@@ -232,6 +232,14 @@ double current = 0.0;
 void
 Editor::update_current_screen ()
 {
+	if (_pending_locate_request) {
+		/* we don't update things when there's a pending locate request, otherwise
+		   when the editor requests a locate there is a chance that this method
+		   will move the playhead before the locate request is processed, causing
+		   a visual glitch. */
+		return;
+	}
+	
 	if (session && session->engine().running()) {
 
 		nframes64_t const frame = session->audible_frame();

gtk2_ardour/editor_mouse.cc

@@ -2429,6 +2429,7 @@ Editor::cursor_drag_finished_callback (ArdourCanvas::Item* item, GdkEvent* event
 	if (item == &playhead_cursor->canvas_item) {
 		if (session) {
 			session->request_locate (playhead_cursor->current_frame, drag_info.was_rolling);
+			_pending_locate_request = true;
 		}
 	} 
 }
@@ -2443,6 +2444,7 @@ Editor::cursor_drag_finished_ensure_locate_callback (ArdourCanvas::Item* item, G
 	if (item == &playhead_cursor->canvas_item) {
 		if (session) {
 			session->request_locate (playhead_cursor->current_frame, drag_info.was_rolling);
+			_pending_locate_request = true;
 		}
 	} 
 }

libs/ardour/ardour/session.h

@@ -371,6 +371,9 @@ class Session : public PBD::StatefulDestructible
 	sigc::signal<void,nframes_t> Xrun;
 	sigc::signal<void> TransportLooped;
 
+	/** emitted when a locate has occurred */
+	sigc::signal<void> Located;
+
 	sigc::signal<void,RouteList&> RouteAdded;
 
 	void request_roll_at_and_return (nframes_t start, nframes_t return_to);

libs/ardour/session_transport.cc

@@ -643,6 +643,10 @@ Session::start_locate (nframes_t target_frame, bool with_roll, bool with_flush,
 
 		}
 
+		/* XXX: not sure if this should be emitted here; perhaps it should happen
+		   when the slave is actually followed */
+		Located (); /* EMIT SIGNAL */
+
 	} else {
 
 		locate (target_frame, with_roll, with_flush, with_loop);