complete emscripten port

https://wiki.libsdl.org/SDL2/README/emscripten
was still up-to-date

.gitignore

@@ -3,4 +3,6 @@
 
 !.gitignore
 !main.cpp
-!screenshot.png
+!screenshot.png
+!build.sh
+!build-web.sh

build-web.sh

@@ -0,0 +1,2 @@
+#!/bin/bash
+/usr/lib/emscripten/em++ -std=c++26 --use-port=sdl2 -O2 --emrun -sASSERTIONS -o index.html main.cpp

build.sh

@@ -0,0 +1,2 @@
+#!/bin/bash
+clang++ -Wall -std=c++26 -O2 -g -o main main.cpp -fuse-ld=mold `pkg-config --libs --cflags sdl2`

main.cpp

@@ -9,6 +9,12 @@
 #include <random>
 #include <source_location>
 #include <stdexcept>
+#include <thread>
+
+#ifdef __EMSCRIPTEN__
+	#include <emscripten.h>
+	#include <emscripten/html5.h>
+#endif
 
 namespace {
 
@@ -53,10 +59,11 @@ auto operator+(SDL_Point a, SDL_Point b) {
 	return SDL_Point{.x = a.x + b.x, .y = a.y + b.y};
 }
 
-// constexpr int width = 1000;
+constexpr int width = 1000;
-// constexpr int height = 1000;
+constexpr int height = 500;
-constexpr int width = 3440;
+
-constexpr int height = 1440;
+// constexpr int width = 3440;
+// constexpr int height = 1440;
 
 template <auto EF>
 struct [[nodiscard("give this a name so SDL_Quit is called at the end"
@@ -79,13 +86,87 @@ auto poll_events(bool& continu) {
 }
 } // namespace
 
+template <typename Loopdata>
+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 = 1000;
+	auto& [renderer, texture, pos, pos1, rne, dist, start_time, next_poll_events_time, next_frame_render_time, frame_start, frame_time, continu] =
+		*static_cast<Loopdata*>(userData);
+
+	// measure frame_time
+	const auto now = clock::now();
+	frame_time = now - frame_start;
+	frame_start = now;
+
+	if (now >= next_poll_events_time) {
+		next_poll_events_time = now + std::chrono::milliseconds{200};
+		poll_events(continu);
+		std::println("last frame_time={} batchsize={}", frame_time, 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_ComposeCustomBlendMode(
+			SDL_BLENDFACTOR_SRC_ALPHA, SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
+			SDL_BLENDOPERATION_ADD, SDL_BLENDFACTOR_ZERO, SDL_BLENDFACTOR_ONE,
+			SDL_BLENDOPERATION_ADD
+		)
+	));
+	sdl_check(SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 32));
+	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;
+	}
+	sdl_check(SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff, 32));
+	sdl_check(
+		SDL_RenderDrawPoints(renderer, point_batch.data(), point_batch.size())
+	);
+	// sdl_check(SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff,
+	// 32)); sdl_check(SDL_RenderFillRect(renderer, nullptr));
+	// SDL_RenderCopy(renderer, fade_texture, nullptr, nullptr);
+
+	///// Render screen
+	sdl_check(SDL_SetRenderTarget(renderer, nullptr));
+	sdl_check(
+		SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, SDL_ALPHA_OPAQUE)
+	);
+	SDL_RenderClear(renderer);
+	sdl_check(SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE));
+	// sdl_check(SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_NONE));
+	sdl_check(SDL_RenderCopy(renderer, texture, nullptr, nullptr));
+	SDL_RenderPresent(renderer);
+}
+
 int main() try {
 	sdl_check(SDL_Init(SDL_INIT_VIDEO));
 	Defer<SDL_Quit> defer_SDL_Quit;
 
 	window_t window{SDL_CreateWindow(
 		"random walk", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width,
-		height, SDL_WINDOW_FULLSCREEN
+		height, 0 // SDL_WINDOW_FULLSCREEN
 	)};
 	renderer_t renderer{SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED)
 	};
@@ -114,85 +195,32 @@ int main() try {
 
 	SDL_Point pos{.x = width / 2, .y = height / 2};
 	SDL_Point pos1{.x = width / 2, .y = height / 2};
-	constexpr SDL_Point directions[] = {
-		{.x = -1, .y = 0}, {.x = 1, .y = 0}, {.x = 0, .y = -1}, {.x = 0, .y = 1}
-	};
 
 	std::mt19937_64 rne(std::random_device{}());
 	std::uniform_int_distribution dist(0, 3);
-	constexpr auto batchsize = 10000;
+	bool continu = true;
 
 	const auto start_time = clock::now();
 	auto next_poll_events_time = start_time;
+	auto next_frame_render_time = start_time;
 	auto frame_start = start_time;
 	clock::duration frame_time;
-	for (bool continu = true; continu;) {
+	auto loopdata = std::tie(
-		// measure frame_time
+		renderer, texture, pos, pos1, rne, dist, start_time,
-		const auto now = clock::now();
+		next_poll_events_time, next_frame_render_time, frame_start, frame_time,
-		frame_time = now - frame_start;
+		continu
-		frame_start = now;
+	);
-
+	std::puts("initialization complete");
-		if (now >= next_poll_events_time) {
+#ifdef __EMSCRIPTEN__
-			next_poll_events_time = now + std::chrono::milliseconds{200};
+	// Receives a function to call and some user data to provide it.
-			poll_events(continu);
+	emscripten_set_main_loop_arg(mainloop<decltype(loopdata)>, &loopdata, 0, 1);
-			std::println(
+#else
-				"last frame_time={} batchsize={}", frame_time, batchsize
+	while (continu) {
-			);
+		mainloop<decltype(loopdata)>(&loopdata);
-		}
+		std::this_thread::sleep_until(next_frame_render_time);
-
+		next_frame_render_time += std::chrono::nanoseconds{16666666};
-		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_ComposeCustomBlendMode(
-				SDL_BLENDFACTOR_SRC_ALPHA, SDL_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
-				SDL_BLENDOPERATION_ADD, SDL_BLENDFACTOR_ZERO,
-				SDL_BLENDFACTOR_ONE, SDL_BLENDOPERATION_ADD
-			)
-		));
-		sdl_check(SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 32));
-		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;
-		}
-		sdl_check(SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff, 32));
-		sdl_check(SDL_RenderDrawPoints(
-			renderer, point_batch.data(), point_batch.size()
-		));
-		// sdl_check(SDL_SetRenderDrawColor(renderer, 0xff, 0xff, 0xff, 32));
-		// sdl_check(SDL_RenderFillRect(renderer, nullptr));
-		// SDL_RenderCopy(renderer, fade_texture, nullptr, nullptr);
-
-		///// Render screen
-		sdl_check(SDL_SetRenderTarget(renderer, nullptr));
-		sdl_check(
-			SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, SDL_ALPHA_OPAQUE)
-		);
-		SDL_RenderClear(renderer);
-		sdl_check(SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE));
-		// sdl_check(SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_NONE));
-		sdl_check(SDL_RenderCopy(renderer, texture, nullptr, nullptr));
-		SDL_RenderPresent(renderer);
 	}
+#endif
 
 	// leaking memory, nothing I can do
 } catch (const std::exception& e) {