src/crepe/api/LoopTimer.cpp


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#include <chrono>

#include "../facade/SDLContext.h"
#include "../util/log.h"

#include "LoopTimer.h"

using namespace crepe;

LoopTimer::LoopTimer() {
    dbg_trace();
}

LoopTimer & LoopTimer::get_instance() {
    static LoopTimer instance;
    return instance;
}

void LoopTimer::start() {
    this->last_frame_time = std::chrono::steady_clock::now();
    this->elapsed_time = std::chrono::milliseconds(0);
    this->elapsed_fixed_time = std::chrono::milliseconds(0);
    this->delta_time = std::chrono::milliseconds(0);
}

void LoopTimer::update() {
    auto current_frame_time = std::chrono::steady_clock::now();
    // Convert to duration in seconds for delta time
    this->delta_time = std::chrono::duration_cast<std::chrono::duration<double>>(current_frame_time - last_frame_time);

    if (this->delta_time > this->maximum_delta_time) {
        this->delta_time = this->maximum_delta_time;
    }

    this->delta_time *= this->game_scale;
    this->elapsed_time += this->delta_time;
    this->last_frame_time = current_frame_time;
}

double LoopTimer::get_delta_time() const {
    return this->delta_time.count();
}

double LoopTimer::get_current_time() const {
    return this->elapsed_time.count();
}

void LoopTimer::advance_fixed_update() {
    this->elapsed_fixed_time += this->fixed_delta_time;
}

double LoopTimer::get_fixed_delta_time() const {
    return this->fixed_delta_time.count();
}

void LoopTimer::set_fps(int fps) {
    this->fps = fps;
	// target time per frame in seconds
    this->frame_target_time = std::chrono::seconds(1) / fps; 
}

int LoopTimer::get_fps() const {
    return this->fps;
}

void LoopTimer::set_game_scale(double value) {
    this->game_scale = value;
}

double LoopTimer::get_game_scale() const {
    return this->game_scale;
}
void LoopTimer::enforce_frame_rate() {
    std::chrono::steady_clock::time_point current_frame_time = std::chrono::steady_clock::now();
    std::chrono::milliseconds frame_duration = std::chrono::duration_cast<std::chrono::milliseconds>(current_frame_time - this->last_frame_time);

    if (frame_duration < this->frame_target_time) {
        std::chrono::milliseconds delay_time = std::chrono::duration_cast<std::chrono::milliseconds>(this->frame_target_time - frame_duration);
        if (delay_time.count() > 0) {
            SDLContext::get_instance().delay(delay_time.count());
        }
    }

    this->last_frame_time = current_frame_time;
}

double LoopTimer::get_lag() const {
    return (this->elapsed_time - this->elapsed_fixed_time).count();
}