fix up some jerkiness/retrograde motion of playhead

git-svn-id: svn://localhost/ardour2/branches/2.0-ongoing@3988 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/editor_cursors.cc

@@ -35,10 +35,7 @@ Editor::Cursor::Cursor (Editor& ed, bool (Editor::*callbck)(GdkEvent*,ArdourCanv
 	  canvas_item (*editor.cursor_group),
 	  length(1.0)
 {
-	
-	/* "randomly" initialize coords */
-	
-	points.push_back(Gnome::Art::Point(1.0, 0.0));
+	points.push_back(Gnome::Art::Point(-1.0, 0.0)); // first x-coord needs to be a non-normal value
 	points.push_back(Gnome::Art::Point(1.0, 1.0));
 
 	canvas_item.property_points() = points;

libs/ardour/ardour/session.h

@@ -1752,6 +1752,11 @@ class Session : public PBD::StatefulDestructible
 	void set_history_depth (uint32_t depth);
 
 	static bool _disable_all_loaded_plugins;
+
+	/* used in ::audible_frame() */
+
+	mutable float af_last_transport_speed;
+	mutable nframes64_t af_last_frame;
 };
 
 } // namespace ARDOUR

libs/ardour/session.cc

@@ -1408,11 +1408,13 @@ Session::audible_frame () const
 	}
 
 	if (_transport_speed == 0) {
-		return tf;
+		ret = tf;
+		goto block_retrograde;
 	}
 
 	if (tf < offset) {
-		return 0;
+		ret = 0;
+		goto block_retrograde;
 	}
 
 	ret = tf;
@@ -1423,9 +1425,39 @@ Session::audible_frame () const
 
 		/* take latency into account */
 		
-		ret -= offset;
+		if (_transport_speed > 0.0) {
+			/* forwards */
+			ret -= offset;
+		} else {
+			/* backwards */
+			ret += offset;
+		}
+
 	}
 
+	/* do not allow retrograde motion near startup or a direction change
+	   caused by latency correction. we detect this by the asking if the present
+	   and previously-noted transport speed (and thus direction) are the same.
+	*/
+
+  block_retrograde:
+	if ((af_last_transport_speed >= 0.0) == (_transport_speed >= 0.0)) {
+
+		if (_transport_speed > 0.0) {
+			if (ret < af_last_frame) {
+				ret = af_last_frame;
+			}
+
+		} else if (_transport_speed < 0.0) {
+			if (ret > af_last_frame) {
+				ret = af_last_frame;
+			}
+		} 
+	} 
+		
+	af_last_frame = ret;
+	af_last_transport_speed = _transport_speed;
+
 	return ret;
 }
 

libs/ardour/session_state.cc

@@ -228,6 +228,8 @@ Session::first_stage_init (string fullpath, string snapshot_name)
 	_smpte_offset = 0;
 	_smpte_offset_negative = true;
 	last_smpte_valid = false;
+	af_last_transport_speed = 0.0;
+	af_last_frame = 0.0;
 
 	sync_time_vars ();
 

svn_revision.h

@@ -1,4 +1,4 @@
 #ifndef __ardour_svn_revision_h__
 #define __ardour_svn_revision_h__
-static const char* ardour_svn_revision = "3963";
+static const char* ardour_svn_revision = "3980";
 #endif