src/crepe/api/LoopTimer.cpp


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

#include "LoopTimer.h"

#define MS_PER_SECOND 1000.0

using namespace crepe;

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

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

void LoopTimer::start() {
    this->last_frame_time = SDLContext::get_instance().get_ticks();
    this->elapsed_time = 0;
    this->elapsed_fixed_time = 0;
    this->delta_time = 0;
}

void LoopTimer::update() {
    uint64_t current_frame_time = SDLContext::get_instance().get_ticks();
    this->delta_time = (current_frame_time - last_frame_time) / MS_PER_SECOND;

    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; }

int LoopTimer::get_current_time() const { return this->elapsed_time; }

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; }

void LoopTimer::set_fps(int fps) {
    this->fps = fps;
    this->frame_target_time = 1.0 / this->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() {
    uint64_t current_frame_time = SDLContext::get_instance().get_ticks();
    double frame_duration = (current_frame_time - this->last_frame_time) / MS_PER_SECOND;

    if (frame_duration < this->frame_target_time) {
        uint32_t delay_time = static_cast<uint32_t>((this->frame_target_time - frame_duration) * MS_PER_SECOND);
        SDLContext::get_instance().delay(delay_time);
    }

    this->last_frame_time = current_frame_time;
}

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