💿🐜 Antkeeper source code
https://antkeeper.com
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93 lines
3.0 KiB
93 lines
3.0 KiB
/*
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* Copyright (C) 2021 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_FRAME_SCHEDULER_HPP
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#define ANTKEEPER_FRAME_SCHEDULER_HPP
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#include <chrono>
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#include <functional>
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/**
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* Schedules fixed-timestep update calls and variable timestep render calls.
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*
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* @see https://gafferongames.com/post/fix_your_timestep/
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*/
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class frame_scheduler
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{
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public:
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frame_scheduler();
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/**
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* Sets the update callback.
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*
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* @param callback Function which takes two parameters: `t`, the total elapsed time, and `dt`, delta time (timestep) which is calculated as `1.0 / update_rate`. This function will be called at the frequency specified by `frame_scheduler::set_update_rate()`.
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*/
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void set_update_callback(std::function<void(double, double)> callback);
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/**
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* Sets the render callback.
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*
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* @param callback Function which takes one parameter: `alpha`, which is a factor that can be used to interpolate between the previous and current update states.
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*/
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void set_render_callback(std::function<void(double)> callback);
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/**
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* Sets the update rate.
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*
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* @param frequency Frequency, in hertz, at which the update callback should be called.
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*/
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void set_update_rate(double frequency);
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/**
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* Sets the maximum duration of a frame. This limits the number of times the update callback is called per frame, thereby preventing a "spiral of death", in which the update callback is called too many times per frame while trying to catch up to the target update rate.
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*
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* @param duration Maximum frame duration, in seconds..
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*/
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void set_max_frame_duration(double duration);
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/**
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* Returns the duration of the last frame, in seconds.
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*/
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double get_frame_duration() const;
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/**
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* Resets the total elapsed time, frame duration, and internal timers.
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*/
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void reset();
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/**
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* Updates the internal timers and performs the scheduled update and render callbacks.
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*/
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void tick();
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private:
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std::function<void(double, double)> update_callback;
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std::function<void(double)> render_callback;
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double update_rate;
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double update_timestep;
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double max_frame_duration;
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double elapsed_time;
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double accumulator;
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std::chrono::high_resolution_clock::time_point frame_start;
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std::chrono::high_resolution_clock::time_point frame_end;
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double frame_duration;
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};
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#endif // ANTKEEPER_FRAME_SCHEDULER_HPP
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