Prevent various things from stopping the transport by requesting a transport speed of exactly 0 when they are really just continuously varying it. Fixes strange playhead behaviour during varispeed when the user varispeeds to exactly 0 and auto-return is triggered.

git-svn-id: svn://localhost/ardour2/branches/3.0@8733 d708f5d6-7413-0410-9779-e7cbd77b26cf

8 files changed, 34 insertions, 18 deletions

diff --git a/gtk2_ardour/ardour_ui2.cc b/gtk2_ardour/ardour_ui2.cc
index 4cd9b71307..1a9b7e53dd 100644
--- a/gtk2_ardour/ardour_ui2.cc
+++ b/gtk2_ardour/ardour_ui2.cc
@@ -816,17 +816,16 @@ ARDOUR_UI::use_shuttle_fract (bool force)
 
 	last_shuttle_request = now;
 
+	double speed = 0;
+
 	if (Config->get_shuttle_units() == Semitones) {
 
 		const double step = 1.0 / 24.0; // range is 24 semitones up & down
 		double semitones;
-		double speed;
 
 		semitones = round (shuttle_fract / step);
 		speed = pow (2.0, (semitones / 12.0));
 
-		_session->request_transport_speed (speed);
-
 	} else {
 
 		bool neg;
@@ -840,9 +839,11 @@ ARDOUR_UI::use_shuttle_fract (bool force)
 			fract = -fract;
 		}
 
-		_session->request_transport_speed (shuttle_max_speed * fract);
+		speed = shuttle_max_speed * fract;
 	}
-
+	
+	_session->request_transport_speed_nonzero (speed);
+	
 	shuttle_box.queue_draw ();
 }
 
diff --git a/gtk2_ardour/editor_mouse.cc b/gtk2_ardour/editor_mouse.cc
index d1d9afc985..e73975ba85 100644
--- a/gtk2_ardour/editor_mouse.cc
+++ b/gtk2_ardour/editor_mouse.cc
@@ -1920,7 +1920,7 @@ Editor::scrub (framepos_t frame, double current_x)
 				scrub_reverse_distance = 0;
 
 				delta = 0.01 * (last_scrub_x - current_x);
-				_session->request_transport_speed (_session->transport_speed() - delta);
+				_session->request_transport_speed_nonzero (_session->transport_speed() - delta);
 			}
 
 		} else {
@@ -1939,7 +1939,7 @@ Editor::scrub (framepos_t frame, double current_x)
 				scrub_reverse_distance = 0;
 
 				delta = 0.01 * (current_x - last_scrub_x);
-				_session->request_transport_speed (_session->transport_speed() + delta);
+				_session->request_transport_speed_nonzero (_session->transport_speed() + delta);
 			}
 		}
 
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index ba39ee47f9..44ab172720 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -303,6 +303,7 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	void use_rf_shuttle_speed ();
 	void allow_auto_play (bool yn);
 	void request_transport_speed (double speed);
+	void request_transport_speed_nonzero (double);
 	void request_overwrite_buffer (Track *);
 	void adjust_playback_buffering();
 	void adjust_capture_buffering();
diff --git a/libs/ardour/session_midi.cc b/libs/ardour/session_midi.cc
index 8dfcec3b5b..ae6d383092 100644
--- a/libs/ardour/session_midi.cc
+++ b/libs/ardour/session_midi.cc
@@ -235,7 +235,7 @@ Session::mmc_step (MIDI::MachineControl &/*mmc*/, int steps)
 	     << endl;
 #endif
 
-	request_transport_speed (step_speed);
+	request_transport_speed_nonzero (step_speed);
 	last_mmc_step = now;
 
 	if (!step_queued) {
@@ -317,9 +317,9 @@ Session::mmc_shuttle (MIDI::MachineControl &/*mmc*/, float speed, bool forw)
 	}
 
 	if (forw) {
-		request_transport_speed (speed);
+		request_transport_speed_nonzero (speed);
 	} else {
-		request_transport_speed (-speed);
+		request_transport_speed_nonzero (-speed);
 	}
 }
 
@@ -535,7 +535,7 @@ Session::mmc_step_timeout ()
 
 	/* slow it down */
 
-	request_transport_speed (_transport_speed * 0.75);
+	request_transport_speed_nonzero (_transport_speed * 0.75);
 	return true;
 }
 
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index de94db6f07..0aab6a7e27 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -107,6 +107,20 @@ Session::request_transport_speed (double speed)
 	queue_event (ev);
 }
 
+/** Request a new transport speed, but if the speed parameter is exactly zero then use
+ *  a very small +ve value to prevent the transport actually stopping.  This method should
+ *  be used by callers who are varying transport speed but don't ever want to stop it.
+ */
+void
+Session::request_transport_speed_nonzero (double speed)
+{
+	if (speed == 0) {
+		speed = DBL_EPSILON;
+	}
+
+	request_transport_speed (speed);
+}
+
 void
 Session::request_track_speed (Track* tr, double speed)
 {
diff --git a/libs/surfaces/frontier/tranzport/tranzport_control_protocol.cc b/libs/surfaces/frontier/tranzport/tranzport_control_protocol.cc
index 7bda9a3e5d..550daef37b 100644
--- a/libs/surfaces/frontier/tranzport/tranzport_control_protocol.cc
+++ b/libs/surfaces/frontier/tranzport/tranzport_control_protocol.cc
@@ -1708,13 +1708,13 @@ TranzportControlProtocol::shuttle ()
 		if (session->transport_speed() < 0) {
 			session->request_transport_speed (1.0);
 		} else {
-			session->request_transport_speed (session->transport_speed() + 0.1);
+			session->request_transport_speed_nonzero (session->transport_speed() + 0.1);
 		}
 	} else {
 		if (session->transport_speed() > 0) {
 			session->request_transport_speed (-1.0);
 		} else {
-			session->request_transport_speed (session->transport_speed() - 0.1);
+			session->request_transport_speed_nonzero (session->transport_speed() - 0.1);
 		}
 	}
 }
diff --git a/libs/surfaces/mackie/mackie_jog_wheel.cc b/libs/surfaces/mackie/mackie_jog_wheel.cc
index 13ea85a7e9..95ab97c5f7 100644
--- a/libs/surfaces/mackie/mackie_jog_wheel.cc
+++ b/libs/surfaces/mackie/mackie_jog_wheel.cc
@@ -76,7 +76,7 @@ void JogWheel::jog_event (SurfacePort &, Control &, const ControlState & state)
 		}
 		
 		// translate _transport_speed speed to a signed transport velocity
-		_mcp.get_session().request_transport_speed( transport_speed() * transport_direction() );
+		_mcp.get_session().request_transport_speed_nonzero (transport_speed() * transport_direction());
 		break;
 	
 	case scrub:
@@ -86,7 +86,7 @@ void JogWheel::jog_event (SurfacePort &, Control &, const ControlState & state)
 			add_scrub_interval( _scrub_timer.restart() );
 			// x clicks per second => speed == 1.0
 			float speed = _mcp.surface().scrub_scaling_factor() / average_scrub_interval() * state.ticks;
-			_mcp.get_session().request_transport_speed( speed * state.sign );
+			_mcp.get_session().request_transport_speed_nonzero (speed * state.sign);
 		}
 		else
 		{
@@ -99,7 +99,7 @@ void JogWheel::jog_event (SurfacePort &, Control &, const ControlState & state)
 	case shuttle:
 		_shuttle_speed = _mcp.get_session().transport_speed();
 		_shuttle_speed += _mcp.surface().scaled_delta( state, _mcp.get_session().transport_speed() );
-		_mcp.get_session().request_transport_speed( _shuttle_speed );
+		_mcp.get_session().request_transport_speed_nonzero (_shuttle_speed);
 		break;
 	
 	case select:
diff --git a/libs/surfaces/tranzport/wheel.cc b/libs/surfaces/tranzport/wheel.cc
index 87b935da4b..baa4ba079b 100644
--- a/libs/surfaces/tranzport/wheel.cc
+++ b/libs/surfaces/tranzport/wheel.cc
@@ -194,13 +194,13 @@ TranzportControlProtocol::shuttle ()
 		if (session->transport_speed() < 0) {
 			session->request_transport_speed (1.0);
 		} else {
-			session->request_transport_speed (session->transport_speed() + 0.1);
+			session->request_transport_speed_nonzero (session->transport_speed() + 0.1);
 		}
 	} else {
 		if (session->transport_speed() > 0) {
 			session->request_transport_speed (-1.0);
 		} else {
-			session->request_transport_speed (session->transport_speed() - 0.1);
+			session->request_transport_speed_nonzero (session->transport_speed() - 0.1);
 		}
 	}
 }