From 7815aa1e89e07e2785d6995b94a28a72a96c74cb Mon Sep 17 00:00:00 2001
From: Colin Fletcher <colin.m.fletcher@googlemail.com>
Date: Fri, 16 May 2014 18:50:30 +0100
Subject: [PATCH] Make tap tempo use g_get_monotonic_time(), and fix minimum
 BPM

gettimeofday() is not guaranteed to be monotonic: use
g_get_monotonic_time() instead.

Also, fix calculation of slowest tap tempo BPM so that the slowest tempo
which can be set by tapping is 10 BPM rather than 240.
---
 gtk2_ardour/tempo_dialog.cc | 14 ++++++--------
 gtk2_ardour/tempo_dialog.h  |  2 +-
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/gtk2_ardour/tempo_dialog.cc b/gtk2_ardour/tempo_dialog.cc
index 56e375dc91..a969581369 100644
--- a/gtk2_ardour/tempo_dialog.cc
+++ b/gtk2_ardour/tempo_dialog.cc
@@ -257,18 +257,16 @@ TempoDialog::pulse_change ()
 void
 TempoDialog::tap_tempo ()
 {
-	struct timeval now;
-	gettimeofday (&now, NULL);
+	gint64 now;
+	now = g_get_monotonic_time (); // microseconds
 
-	if (last_tap.tv_sec >= 0 || last_tap.tv_usec > 0) {
-		struct timeval diff;
+	if (last_tap > 0) {
 		double interval, bpm;
 		static const double decay = 0.5;
 
-		timersub (&now, &last_tap, &diff);
-		interval = diff.tv_sec + diff.tv_usec * 1.0e-6;
-		if (interval <= 0.25) {
-			// >= 15 bpm, say
+		interval = (now - last_tap) * 1.0e-6;
+		if (interval <= 6.0) {
+			// >= 10 bpm, say
 			if (average_interval > 0) {
 				average_interval = interval * decay
 					+ average_interval * (1.0-decay);
diff --git a/gtk2_ardour/tempo_dialog.h b/gtk2_ardour/tempo_dialog.h
index 9e97afa98d..616be2433e 100644
--- a/gtk2_ardour/tempo_dialog.h
+++ b/gtk2_ardour/tempo_dialog.h
@@ -57,7 +57,7 @@ private:
 	typedef std::map<std::string,float> NoteTypes;
 	NoteTypes note_types;
 
-	struct timeval last_tap;
+	gint64 last_tap;
 	double average_interval;
 
 	Gtk::ComboBoxText pulse_selector;