From f18132d6742a42e4d7423cc23d1382d374e97abf Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 5 Mar 2019 22:01:58 -0500
Subject: [PATCH] Makes effort to round out draft 1 of
 Outputs::Display::Metrics.

---
 Outputs/DisplayMetrics.cpp | 19 ++++++++++++++-----
 Outputs/DisplayMetrics.hpp | 15 ++++++++++++++-
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/Outputs/DisplayMetrics.cpp b/Outputs/DisplayMetrics.cpp
index 3814298d2..3df043af6 100644
--- a/Outputs/DisplayMetrics.cpp
+++ b/Outputs/DisplayMetrics.cpp
@@ -8,7 +8,7 @@
 
 #include "DisplayMetrics.hpp"
 
-#include <iostream>
+#include <numeric>
 
 using namespace Outputs::Display;
 
@@ -19,8 +19,10 @@ void Metrics::announce_event(ScanTarget::Event event) {
 		case ScanTarget::Event::EndHorizontalRetrace:
 			++lines_this_frame_;
 		break;
-		case ScanTarget::Event::EndVerticalRetrace:
+		case ScanTarget::Event::BeginVerticalRetrace:
 			add_line_total(lines_this_frame_);
+		break;
+		case ScanTarget::Event::EndVerticalRetrace:
 			lines_this_frame_ = 0;
 		break;
 		default: break;
@@ -28,11 +30,18 @@ void Metrics::announce_event(ScanTarget::Event event) {
 }
 
 void Metrics::add_line_total(int total) {
-//	std::cout << total << '\n';
+	line_total_history_[line_total_history_pointer_] = total;
+	line_total_history_pointer_ = (line_total_history_pointer_ + 1) % line_total_history_.size();
 }
 
-float Metrics::lines_per_frame_estimate() {
-	return 1.0f;	// TODO.
+float Metrics::visible_lines_per_frame_estimate() {
+	// Just average the number of records contained in line_total_history_ to provide this estimate;
+	// that array should be an even number, to allow for potential interlaced sources.
+	return float(std::accumulate(line_total_history_.begin(), line_total_history_.end(), 0)) / float(line_total_history_.size());
+}
+
+int Metrics::current_line() {
+	return lines_this_frame_;
 }
 
 // MARK: GPU processing speed decisions.
diff --git a/Outputs/DisplayMetrics.hpp b/Outputs/DisplayMetrics.hpp
index 77eccad1a..4854e950b 100644
--- a/Outputs/DisplayMetrics.hpp
+++ b/Outputs/DisplayMetrics.hpp
@@ -10,6 +10,8 @@
 #define DisplayMetrics_hpp
 
 #include "ScanTarget.hpp"
+
+#include <array>
 #include <chrono>
 
 namespace Outputs {
@@ -22,16 +24,27 @@ namespace Display {
 */
 class Metrics {
 	public:
+		/// Notifies Metrics of a beam event.
 		void announce_event(ScanTarget::Event event);
 
+		/// Notifies Metrics that the size of the output buffer has changed.
 		void announce_did_resize();
+		/// Provides Metrics with a new data point for output speed estimation.
 		void announce_draw_status(size_t lines, std::chrono::high_resolution_clock::duration duration, bool complete);
 
+		/// @returns @c true if Metrics thinks a lower output buffer resolution is desirable in the abstract; @c false otherwise.
 		bool should_lower_resolution();
-		float lines_per_frame_estimate();
+
+		/// @returns An estimate of the number of lines being produced per frame, excluding vertical sync.
+		float visible_lines_per_frame_estimate();
+
+		/// @returns The number of lines since vertical retrace ended.
+		int current_line();
 
 	private:
 		int lines_this_frame_ = 0;
+		std::array<int, 20> line_total_history_;
+		size_t line_total_history_pointer_ = 0;
 		void add_line_total(int);
 
 		int frames_hit_ = 0;