Update locations GUI more efficiently by avoiding a rebuild when a location is removed. Fixes #3263.

git-svn-id: svn://localhost/ardour2/branches/3.0@7290 d708f5d6-7413-0410-9779-e7cbd77b26cf

2 files changed, 17 insertions, 10 deletions

diff --git a/libs/ardour/ardour/location.h b/libs/ardour/ardour/location.h
index f23d2e382a..7d3b0ac1a9 100644
--- a/libs/ardour/ardour/location.h
+++ b/libs/ardour/ardour/location.h
@@ -163,15 +163,23 @@ class Locations : public PBD::StatefulDestructible
 	int set_current (Location *, bool want_lock = true);
 	Location *current () const { return current_location; }
 
-	Location *first_location_before (nframes64_t, bool include_special_ranges = false);
-	Location *first_location_after (nframes64_t, bool include_special_ranges = false);
+	Location* first_location_before (nframes64_t, bool include_special_ranges = false);
+	Location* first_location_after (nframes64_t, bool include_special_ranges = false);
 
 	void marks_either_side (nframes64_t const, nframes64_t &, nframes64_t &) const;
 
 	void find_all_between (nframes64_t start, nframes64_t, LocationList&, Location::Flags);
 
+	enum Change {
+		ADDITION, ///< a location was added, but nothing else changed
+		REMOVAL, ///< a location was removed, but nothing else changed
+		OTHER ///< something more complicated happened
+	};
+
 	PBD::Signal1<void,Location*> current_changed;
-	PBD::Signal0<void>           changed;
+	/** something changed about the location list; the parameter gives some idea as to what */
+	PBD::Signal1<void,Change>    changed;
+	/** a location has been added to the end of the list */
 	PBD::Signal1<void,Location*> added;
 	PBD::Signal1<void,Location*> removed;
 	PBD::Signal1<void,const PBD::PropertyChange&>    StateChanged;
diff --git a/libs/ardour/location.cc b/libs/ardour/location.cc
index 7202e1ef03..93b6b5c5fa 100644
--- a/libs/ardour/location.cc
+++ b/libs/ardour/location.cc
@@ -492,7 +492,7 @@ Locations::clear ()
 		current_location = 0;
 	}
 
-	changed (); /* EMIT SIGNAL */
+	changed (OTHER); /* EMIT SIGNAL */
 	current_changed (0); /* EMIT SIGNAL */
 }
 
@@ -515,7 +515,7 @@ Locations::clear_markers ()
 		}
 	}
 
-	changed (); /* EMIT SIGNAL */
+	changed (OTHER); /* EMIT SIGNAL */
 }
 
 void
@@ -541,7 +541,7 @@ Locations::clear_ranges ()
 		current_location = 0;
 	}
 
-	changed (); /* EMIT SIGNAL */
+	changed (OTHER); /* EMIT SIGNAL */
 	current_changed (0); /* EMIT SIGNAL */
 }
 
@@ -568,7 +568,6 @@ Locations::add (Location *loc, bool make_current)
 
 void
 Locations::remove (Location *loc)
-
 {
 	bool was_removed = false;
 	bool was_current = false;
@@ -602,14 +601,14 @@ Locations::remove (Location *loc)
 			 current_changed (0); /* EMIT SIGNAL */
 		}
 
-		changed (); /* EMIT_SIGNAL */
+		changed (REMOVAL); /* EMIT_SIGNAL */
 	}
 }
 
 void
 Locations::location_changed (Location* /*loc*/)
 {
-	changed (); /* EMIT SIGNAL */
+	changed (OTHER); /* EMIT SIGNAL */
 }
 
 XMLNode&
@@ -701,7 +700,7 @@ Locations::set_state (const XMLNode& node, int version)
 		}
 	}
 
-	changed (); /* EMIT SIGNAL */
+	changed (OTHER); /* EMIT SIGNAL */
 
 	return 0;
 }