From f5704b6d841a30962f1c79b5eaed3a53452288c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakob=20H=C3=B6rdt?=
 <6329417-neop_@users.noreply.gitlab.com>
Date: Sun, 4 Aug 2024 02:07:41 +0200
Subject: [PATCH] automatically adjust batchsize to walk as fast as possible

---
 main.cpp | 38 ++++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/main.cpp b/main.cpp
index a39e826..1835dce 100644
--- a/main.cpp
+++ b/main.cpp
@@ -35,8 +35,10 @@ auto operator==(const SDL_Point& a, const SDL_Point& b) {
 	return a.x == b.x && a.y == b.y;
 }
 
-constexpr int width = 1000;
-constexpr int height = 1000;
+// constexpr int width = 1000;
+// constexpr int height = 1000;
+constexpr int width = 3440;
+constexpr int height = 1300;
 
 template <auto EF>
 struct [[nodiscard("give this a name so SDL_Quit is called at the end"
@@ -97,14 +99,34 @@ int main() {
 	std::mt19937_64 rne(std::random_device{}());
 	std::uniform_int_distribution dist(0, 3);
 	//                              aarrggbb??
-	constexpr Uint32 walk_color = 0xff00ff00;
+	constexpr Uint32 bg_color = 0xffdbd7c0;
+	constexpr Uint32 walk_color = 0xff0d0f14;
+
+	SDL_LockSurface(window_surface);
+	for (int i = 0; i < window_surface->w * window_surface->h; ++i) {
+		static_cast<Uint32*>(window_surface->pixels)[i] = bg_color;
+	}
+	SDL_UnlockSurface(window_surface);
+
+	auto batchsize = 100.0;
+	constexpr auto frametime_target = std::chrono::milliseconds{10};
 
 	const auto start_time = clock::now();
 	auto next_poll_events_time = start_time;
+	auto frame_start = start_time - frametime_target;
+	clock::duration frame_time = frametime_target;
 	for (bool continu = true; continu;) {
+		{
+			// measure frame_time
+			auto now = clock::now();
+			frame_time = now - frame_start;
+			frame_start = now;
+		}
+
+		batchsize = batchsize * (0.9 + 0.1 * frametime_target / frame_time);
 
 		SDL_LockSurface(window_surface);
-		for (auto batch = 0z; batch < 1000; ++batch) {
+		for (auto step = 0z; step < int(batchsize); ++step) {
 			SDL_Point newpoint;
 			do {
 				newpoint = pos + directions[dist(rne)];
@@ -112,15 +134,19 @@ int main() {
 			         newpoint.y >= height);
 			pos = newpoint;
 			static_cast<Uint32*>(window_surface->pixels
-			)[pos.x + pos.y * window_surface->h] = walk_color;
+			)[pos.x + pos.y * window_surface->w] = walk_color;
 		}
 		SDL_UnlockSurface(window_surface);
+
 		SDL_UpdateWindowSurface(window);
 
 		const auto now = clock::now();
 		if (now >= next_poll_events_time) {
-			next_poll_events_time = now + std::chrono::milliseconds{100};
+			next_poll_events_time = now + std::chrono::milliseconds{200};
 			poll_events(continu);
+			std::println(
+				"last frame_time={} batchsize={}", frame_time, batchsize
+			);
 		}
 	}