From 944aa08e294aa36cee5169d26b94b922d5850e62 Mon Sep 17 00:00:00 2001
From: MrHeadwar <edwsaintesprit@hotmail.com>
Date: Fri, 6 Jan 2023 11:22:37 +0100
Subject: [PATCH] Tempo dialog : added a measure of accuracy to the Tap Tempo
 function

---
 gtk2_ardour/tempo_dialog.cc | 35 +++++++++++++++++++++++++++++------
 gtk2_ardour/tempo_dialog.h  |  3 +++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/gtk2_ardour/tempo_dialog.cc b/gtk2_ardour/tempo_dialog.cc
index 36cba7ea55d..c8b9af5ac58 100644
--- a/gtk2_ardour/tempo_dialog.cc
+++ b/gtk2_ardour/tempo_dialog.cc
@@ -246,7 +246,7 @@ TempoDialog::init (const Temporal::BBT_Time& when, double bpm, double end_bpm, d
 	get_vbox ()->pack_end (*table, false, false);
 	table->show_all ();
 
-	table = manage (new Table (2, 2));
+	table = manage (new Table (3, 2));
 	table->set_spacings (6);
 	row = 0;
 
@@ -254,6 +254,9 @@ TempoDialog::init (const Temporal::BBT_Time& when, double bpm, double end_bpm, d
 	table->attach (_midi_port_combo, 1, 2, row, row + 1);
 	++row;
 	table->attach (tap_tempo_button, 0, 2, row, row + 1);
+	++row;
+	pbar.hide();
+	table->attach (pbar, 0, 2, row, row + 1);
 
 	get_vbox()->pack_end (*table, false, false);
 	table->show_all ();
@@ -297,7 +300,7 @@ TempoDialog::init (const Temporal::BBT_Time& when, double bpm, double end_bpm, d
 
 	/* init state */
 	tempo_type_change ();
-	tapped = false;
+	toggle_tap(false);
 #if 0
 	bpm_spinner.select_region (0, -1);
 	bpm_spinner.grab_focus ();
@@ -313,6 +316,17 @@ TempoDialog::~TempoDialog ()
 	AudioEngine::instance ()->unregister_port (_midi_tap_port);
 }
 
+void
+TempoDialog::toggle_tap (bool active)
+{
+	tapped = active;
+	if (active) {
+		pbar.show();
+	} else {
+		pbar.hide();
+	}
+}
+
 void
 TempoDialog::midi_event (MIDI::byte* msg, size_t len, MIDI::samplecnt_t now)
 {
@@ -387,7 +401,7 @@ void
 TempoDialog::port_changed ()
 {
 	bool rv = false;
-	tapped  = false;
+	toggle_tap(false);
 	_midi_tap_port->disconnect_all ();
 	TreeModel::iterator r = _midi_port_combo.get_active ();
 	if (r) {
@@ -575,12 +589,21 @@ TempoDialog::tap_tempo (int64_t usec)
 		sum_x += n;
 		sum_xy += n * t;
 		sum_xx += n * n;
+		
 		double T = (sum_xy / n - sum_x / n * sum_y / n) / (sum_xx / n - sum_x / n * sum_x / n);
+		/* Statistical error (95th percentile) is less relevant than considering the operator has the right 
+		 * number of pulses but an error of 1/2 period at the beggining and end so max error = 1 period */
+		double dT = T - (sum_xy / (n + 1) - sum_x / (n + 1) * sum_y / (n + 1)) / (sum_xx / (n + 1) - sum_x / (n + 1) * sum_x / (n + 1));
 
 		if (t - last_t < T / 1.2 || t - last_t > T * 1.2 || T <= .06 || T > 60) {
-			tapped = false;
+			toggle_tap(false);
 		} else {
 			bpm_spinner.set_value (60.0 / T);
+			if (T != 0) {
+				double accuracy = 1 - dT / T;
+				pbar.set_text(string_compose(_("Accuracy : %1 %% (+/- %2 BpM)"),(int)(accuracy * 100),60.0 * dT / (T * (T + dT))));
+				pbar.set_fraction (accuracy);
+			}
 		}
 	}
 	if (!tapped) {
@@ -592,7 +615,7 @@ TempoDialog::tap_tempo (int64_t usec)
 		sum_xx    = 1.0;
 		tap_count = 1.0;
 
-		tapped = true;
+		toggle_tap(true);
 	}
 	tap_count++;
 	last_t = t;
@@ -601,7 +624,7 @@ TempoDialog::tap_tempo (int64_t usec)
 bool
 TempoDialog::tap_tempo_focus_out (GdkEventFocus* )
 {
-	tapped = false;
+	toggle_tap(false);
 	return false;
 }
 
diff --git a/gtk2_ardour/tempo_dialog.h b/gtk2_ardour/tempo_dialog.h
index f583c5f27ba..f9f279c7764 100644
--- a/gtk2_ardour/tempo_dialog.h
+++ b/gtk2_ardour/tempo_dialog.h
@@ -36,6 +36,7 @@
 #include <gtkmm/spinbutton.h>
 #include <gtkmm/combobox.h>
 #include <gtkmm/comboboxtext.h>
+#include <gtkmm/progressbar.h>
 
 #include "ardour/types.h"
 #include "ardour/tempo.h"
@@ -82,6 +83,7 @@ class TempoDialog : public ArdourDialog
 	void ports_changed ();
 
 	void tap_tempo (int64_t);
+	void toggle_tap (bool);
 	void midi_event (MIDI::byte*, size_t, MIDI::samplecnt_t);
 
 	typedef std::map<std::string,int> NoteTypes;
@@ -118,6 +120,7 @@ class TempoDialog : public ArdourDialog
 	Gtk::ComboBoxText tempo_type;
 	Gtk::ComboBoxText lock_style;
 	Gtk::ComboBox _midi_port_combo;
+	Gtk::ProgressBar pbar;
 
 	class MidiPortCols : public Gtk::TreeModelColumnRecord
 	{