From 3212f868ec72fed320438a1f5722c527627092c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakob=20H=C3=B6rdt?=
 <6329417-neop_@users.noreply.gitlab.com>
Date: Thu, 8 Aug 2024 00:13:13 +0200
Subject: [PATCH] abstract multiple walkers

---
 main.cpp | 85 ++++++++++++++++++++++++++++----------------------------
 1 file changed, 42 insertions(+), 43 deletions(-)

diff --git a/main.cpp b/main.cpp
index 783fcf1..ef0eebd 100644
--- a/main.cpp
+++ b/main.cpp
@@ -62,9 +62,9 @@ auto operator+(SDL_Point a, SDL_Point b) {
 
 using clock = std::chrono::steady_clock;
 
-constexpr int width = 1000;
-constexpr int height = 500;
-constexpr auto steps_per_second = 3;
+constexpr int width = 2000;
+constexpr int height = 1000;
+constexpr auto steps_per_second = 100'000;
 
 template <auto EF>
 struct [[nodiscard("give this a name so SDL_Quit is called at the end"
@@ -83,6 +83,11 @@ auto poll_events(bool& continu) {
 		if (e.type == SDL_QUIT) { continu = false; }
 	}
 }
+
+struct Walker {
+	SDL_Point pos;
+	SDL_Color col;
+};
 } // namespace
 
 template <typename Loopdata>
@@ -90,8 +95,7 @@ void mainloop(void* userData) {
 	constexpr SDL_Point directions[] = {
 		{.x = -1, .y = 0}, {.x = 1, .y = 0}, {.x = 0, .y = -1}, {.x = 0, .y = 1}
 	};
-	constexpr auto batchsize = 1;
-	auto& [renderer, texture, pos, pos1, rne, dist, start_time, total_steps, next_poll_events_time, next_frame_render_time, frame_start, frame_time, continu] =
+	auto& [renderer, texture, walkers, rne, dist, start_time, total_steps, next_poll_events_time, next_frame_render_time, frame_start, frame_time, continu] =
 		*static_cast<Loopdata*>(userData);
 
 	// measure frame_time
@@ -101,52 +105,39 @@ void mainloop(void* userData) {
 
 	// possibly poll events
 	if (now >= next_poll_events_time) {
-		next_poll_events_time = now + std::chrono::milliseconds{200};
+		next_poll_events_time = now + std::chrono::milliseconds{20};
 		poll_events(continu);
 	}
 
-	// simulate steps for passed time
+	// simulate steps for passed time //
+	// roughly make a batch for every millisecond
+	constexpr auto batchsize =
+		std::clamp(steps_per_second / 1000 /*ms*/, 1, 1000);
 	const auto total_time = now - start_time;
 	const auto target_total_steps = total_time * steps_per_second /
 	                                clock::duration{std::chrono::seconds{1}};
-	std::print(
-		"total_time={} total_steps={} target={}\r", total_time, total_steps,
-		target_total_steps
-	);
-
 	for (; total_steps + batchsize <= target_total_steps;
 	     total_steps += batchsize) {
-		std::array<SDL_Point, batchsize> point_batch;
-		for (auto step = 0z; step < batchsize; ++step) {
-			SDL_Point newpoint;
-			do {
-				newpoint = pos + directions[dist(rne)];
-			} while (newpoint.x < 0 or newpoint.x >= width or newpoint.y < 0 or
-			         newpoint.y >= height);
-			pos = newpoint;
-			point_batch[step] = newpoint;
-		}
-
-		///// Render image
 		sdl_check(SDL_SetRenderTarget(renderer, texture));
 		sdl_check(SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND));
-		sdl_check(SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0xff));
-		sdl_check(SDL_RenderDrawPoints(
-			renderer, point_batch.data(), point_batch.size()
-		));
-		for (auto step = 0z; step < batchsize; ++step) {
-			SDL_Point newpoint;
-			do {
-				newpoint = pos1 + directions[dist(rne)];
-			} while (newpoint.x < 0 or newpoint.x >= width or newpoint.y < 0 or
-			         newpoint.y >= height);
-			pos1 = newpoint;
-			point_batch[step] = newpoint;
+		for (auto& walker : walkers) {
+			sdl_check(SDL_SetRenderDrawColor(
+				renderer, walker.col.r, walker.col.g, walker.col.b, walker.col.a
+			));
+			std::array<SDL_Point, batchsize> point_batch;
+			for (auto step = 0z; step < batchsize; ++step) {
+				SDL_Point newpoint;
+				do {
+					newpoint = walker.pos + directions[dist(rne)];
+				} while (newpoint.x < 0 or newpoint.x >= width or
+				         newpoint.y < 0 or newpoint.y >= height);
+				walker.pos = newpoint;
+				point_batch[step] = newpoint;
+			}
+			sdl_check(SDL_RenderDrawPoints(
+				renderer, point_batch.data(), point_batch.size()
+			));
 		}
-		sdl_check(SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff, 0xff));
-		sdl_check(SDL_RenderDrawPoints(
-			renderer, point_batch.data(), point_batch.size()
-		));
 	}
 
 	///// Render screen
@@ -193,8 +184,16 @@ int main() try {
 	);
 	sdl_check(SDL_RenderClear(renderer));
 
-	SDL_Point pos{.x = width / 2, .y = height / 2};
-	SDL_Point pos1{.x = width / 2, .y = height / 2};
+	auto walkers = std::to_array<Walker>(
+		{{.pos = {.x = width / 2, .y = height / 2},
+	      .col = {.r = 0xff, .g = 0x00, .b = 0x00, .a = 0xff}},
+	     {.pos = {.x = width / 2, .y = height / 2},
+	      .col = {.r = 0x00, .g = 0xff, .b = 0x00, .a = 0xff}},
+	     {.pos = {.x = width / 2, .y = height / 2},
+	      .col = {.r = 0x00, .g = 0x00, .b = 0xff, .a = 0xff}},
+	     {.pos = {.x = width / 2, .y = height / 2},
+	      .col = {.r = 0x00, .g = 0x00, .b = 0x00, .a = 0xff}}}
+	);
 
 	std::mt19937_64 rne(std::random_device{}());
 	std::uniform_int_distribution dist(0, 3);
@@ -207,7 +206,7 @@ int main() try {
 	auto total_steps = 0ll;
 	clock::duration frame_time;
 	auto loopdata = std::tie(
-		renderer, texture, pos, pos1, rne, dist, start_time, total_steps,
+		renderer, texture, walkers, rne, dist, start_time, total_steps,
 		next_poll_events_time, next_frame_render_time, frame_start, frame_time,
 		continu
 	);