////////////////////////////////////////////////////////////////////////////////

// Distributed under the Boost Software License, Version 1.0. //

// (See accompanying file LICENSE or copy at //

// https://www.boost.org/LICENSE_1_0.txt) //

////////////////////////////////////////////////////////////////////////////////

#include "core/looper.h"

#include <chrono>

namespace iris

{

Looper::Looper(

std::chrono::microseconds clock,

std::chrono::microseconds timestep,

LoopFunction fixed_timestep,

LoopFunction variable_timestep)

: clock_(clock)

, timestep_(timestep)

, fixed_timestep_(fixed_timestep)

, variable_timestep_(variable_timestep)

{

}

void Looper::run()

{

auto run = true;

auto start = std::chrono::steady_clock::now();

std::chrono::steady_clock::duration accumulator(0);

do

{

// calculate duration of last frame

const auto end = std::chrono::steady_clock::now();

const auto frame_time = end - start;

start = end;

// variable time step function produces time

accumulator += frame_time;

// fixed time step function consumed time

while (run && (accumulator >= timestep_))

{

run &= fixed_timestep_(clock_, timestep_);

accumulator -= timestep_;

clock_ += timestep_;

}

run &= variable_timestep_(clock_, std::chrono::duration_cast<std::chrono::microseconds>(frame_time));

} while (run);

}

}