From 2d20bcab4a0a7787f61c15679988c6db47c2ca60 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 10 Mar 2015 10:52:44 +0100
Subject: [PATCH] dramatically reduce ShuttleControl CPU usage

---
 gtk2_ardour/ardour_ui.cc       |  3 ++-
 gtk2_ardour/shuttle_control.cc | 23 ++++++++++-------------
 gtk2_ardour/shuttle_control.h  |  3 +--
 3 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/gtk2_ardour/ardour_ui.cc b/gtk2_ardour/ardour_ui.cc
index 4998d4b771..8b8a7cdef2 100644
--- a/gtk2_ardour/ardour_ui.cc
+++ b/gtk2_ardour/ardour_ui.cc
@@ -1141,7 +1141,8 @@ ARDOUR_UI::every_second ()
 void
 ARDOUR_UI::every_point_one_seconds ()
 {
-	shuttle_box->update_speed_display ();
+	// TODO get rid of this..
+	// ShuttleControl is updated directly via TransportStateChange signal
 }
 
 void
diff --git a/gtk2_ardour/shuttle_control.cc b/gtk2_ardour/shuttle_control.cc
index 654785d435..2efda697a1 100644
--- a/gtk2_ardour/shuttle_control.cc
+++ b/gtk2_ardour/shuttle_control.cc
@@ -132,6 +132,15 @@ ShuttleControl::map_transport_state ()
 {
 	float speed = _session->transport_speed ();
 
+	if ( (fabsf( speed - last_speed_displayed) < 0.005f) // dead-zone
+			&& !( speed == 1.f && last_speed_displayed != 1.f)
+			&& !( speed == 0.f && last_speed_displayed != 0.f)
+	   )
+	{
+		return; // nothing to see here, move along.
+	}
+
+	// Q: is there a good reason why we  re-calculate this every time?
 	if (fabs(speed) <= (2*DBL_EPSILON)) {
 		shuttle_fract = 0;
 	} else {
@@ -232,6 +241,7 @@ void
 ShuttleControl::set_shuttle_max_speed (float speed)
 {
 	shuttle_max_speed = speed;
+	last_speed_displayed = -99999999;
 }
 
 bool
@@ -637,19 +647,6 @@ ShuttleControl::set_shuttle_units (ShuttleUnits s)
 	Config->set_shuttle_units (s);
 }
 
-void
-ShuttleControl::update_speed_display ()
-{
-	const float speed = _session->transport_speed();
-	if ( (fabsf( speed - last_speed_displayed) > 0.009f) // dead-zone just below 1%, except..
-			|| ( speed == 1.f && last_speed_displayed != 1.f)
-			|| ( speed == 0.f && last_speed_displayed != 0.f)
-	   )
-	{
-		queue_draw ();
-	}
-}
-
 ShuttleControl::ShuttleControllable::ShuttleControllable (ShuttleControl& s)
 	: PBD::Controllable (X_("Shuttle"))
 	, sc (s)
diff --git a/gtk2_ardour/shuttle_control.h b/gtk2_ardour/shuttle_control.h
index 0b289c5180..21b02d9954 100644
--- a/gtk2_ardour/shuttle_control.h
+++ b/gtk2_ardour/shuttle_control.h
@@ -39,8 +39,7 @@ class ShuttleControl : public CairoWidget, public ARDOUR::SessionHandlePtr
 	~ShuttleControl ();
 
 	void map_transport_state ();
-	void update_speed_display ();
-        void set_shuttle_fract (double, bool zero_ok = false);
+	void set_shuttle_fract (double, bool zero_ok = false);
 	double get_shuttle_fract () const { return shuttle_fract; }
 	void set_session (ARDOUR::Session*);