godot/platform/web/web_main.cpp

/*************************************************************************/
/*  web_main.cpp                                                         */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
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#include "core/config/engine.h"
#include "core/io/resource_loader.h"
#include "main/main.h"
#include "platform/web/display_server_web.h"
#include "platform/web/os_web.h"

#include <emscripten/emscripten.h>
#include <stdlib.h>

#include "godot_js.h"

static OS_Web *os = nullptr;
static uint64_t target_ticks = 0;
static bool main_started = false;
static bool shutdown_complete = false;

void exit_callback() {
	if (!shutdown_complete) {
		return; // Still waiting.
	}
	if (main_started) {
		Main::cleanup();
		main_started = false;
	}
	int exit_code = OS_Web::get_singleton()->get_exit_code();
	memdelete(os);
	os = nullptr;
	emscripten_force_exit(exit_code); // Exit runtime.
}

void cleanup_after_sync() {
	shutdown_complete = true;
}

void main_loop_callback() {
	uint64_t current_ticks = os->get_ticks_usec();

	bool force_draw = DisplayServerWeb::get_singleton()->check_size_force_redraw();
	if (force_draw) {
		Main::force_redraw();
	} else if (current_ticks < target_ticks) {
		return; // Skip frame.
	}

	int max_fps = Engine::get_singleton()->get_max_fps();
	if (max_fps > 0) {
		if (current_ticks - target_ticks > 1000000) {
			// When the window loses focus, we stop getting updates and accumulate delay.
			// For this reason, if the difference is too big, we reset target ticks to the current ticks.
			target_ticks = current_ticks;
		}
		target_ticks += (uint64_t)(1000000 / max_fps);
	}
	if (os->main_loop_iterate()) {
		emscripten_cancel_main_loop(); // Cancel current loop and set the cleanup one.
		emscripten_set_main_loop(exit_callback, -1, false);
		godot_js_os_finish_async(cleanup_after_sync);
	}
}

/// When calling main, it is assumed FS is setup and synced.
extern EMSCRIPTEN_KEEPALIVE int godot_web_main(int argc, char *argv[]) {
	os = new OS_Web();

	// We must override main when testing is enabled
	TEST_MAIN_OVERRIDE

	Error err = Main::setup(argv[0], argc - 1, &argv[1]);

	// Proper shutdown in case of setup failure.
	if (err != OK) {
		int exit_code = (int)err;
		if (err == ERR_HELP) {
			exit_code = 0; // Called with --help.
		}
		os->set_exit_code(exit_code);
		// Will only exit after sync.
		emscripten_set_main_loop(exit_callback, -1, false);
		godot_js_os_finish_async(cleanup_after_sync);
		return exit_code;
	}

	os->set_exit_code(0);
	main_started = true;

	// Ease up compatibility.
	ResourceLoader::set_abort_on_missing_resources(false);

	Main::start();
	os->get_main_loop()->initialize();
#ifdef TOOLS_ENABLED
	if (Engine::get_singleton()->is_project_manager_hint() && FileAccess::exists("/tmp/preload.zip")) {
		PackedStringArray ps;
		ps.push_back("/tmp/preload.zip");
		os->get_main_loop()->emit_signal(SNAME("files_dropped"), ps, -1);
	}
#endif
	emscripten_set_main_loop(main_loop_callback, -1, false);
	// Immediately run the first iteration.
	// We are inside an animation frame, we want to immediately draw on the newly setup canvas.
	main_loop_callback();

	return 0;
}