Mortis game loop template

gameloop.cpp

#define STB_TRUETYPE_IMPLEMENTATION
#define STB_IMAGE_IMPLEMENTATION

#include "glm/glm/glm.hpp"
#include "glm/glm/ext.hpp"
#include "stb/stb_truetype.h"
#include "stb/stb_image.h"
#include "zen/sdlu.h"
#include "zen/glut.h"
#include "zen/zen.h"


const int WINDOW_WIDTH = 1024;
const int WINDOW_HEIGHT = 768;

const float fixedTimestep = 0.01f;
float accumulator = 0.0f;


float previousState;
float currentState;


uint32_t fontID;


void setup() {

	previousState = 0.0f;
	currentState = 0.0f;

	SDL::createWindow("Lua Test", WINDOW_WIDTH, WINDOW_HEIGHT);

	glut::init();

	// loading a font
	uint8_t *file = SDL::loadFile("../fonts/FreePixel.ttf");
	fontID = glut::loadFont(file, 16);
	SDL::freeFile(file);

	glut::setupMultisampler(WINDOW_WIDTH, WINDOW_HEIGHT, 8);

	SDL::showWindow();
}


void shutdown() {

	SDL::destroyWindow();

}


void fixedUpdate() {

	previousState = currentState;
	currentState += fixedTimestep * 10;
	
	if (currentState > WINDOW_WIDTH) {
		currentState = 0;
	}
}


void update() {

}


void input() {

	SDL::window.shouldClose = SDL::keyDown(ESCAPE);

}


void render(float alpha) {

	float xpos = (1.0f - alpha) * previousState + alpha * currentState;
	float ypos = 200.0f;
	float radius = 42.0f;
	glm::vec2 xy0(xpos - radius, ypos - radius);
	glm::vec2 xy1(xpos + radius, ypos + radius);
	float z = -0.5;
	glm::vec4 color(0.0f, 1.0f, 0.0f, 0.5f);
	glm::mat4 mat = glm::ortho(0.0f, (float)WINDOW_WIDTH, (float)WINDOW_HEIGHT, 0.0f, 0.1f, 1.0f);
	glut::drawRect(&xy0[0], &xy1[0], z, &color[0], &mat[0][0]);

}


int main(int argc, char *argv[]) {

	setup();	

	SDL::createWindow("Lua Test", WINDOW_WIDTH, WINDOW_HEIGHT);

	glut::init();

	// loading a font
	uint8_t *file = SDL::loadFile("../fonts/FreePixel.ttf");
	fontID = glut::loadFont(file, 16);
	SDL::freeFile(file);

	glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
	glut::setupMultisampler(WINDOW_WIDTH, WINDOW_HEIGHT, 8);

	SDL::showWindow();
	while (SDL::isRunning()) {

		glut::initFrame();
		SDL::beginFrame();

		float frameTime = SDL::frame.deltaTime;
		if (frameTime < 0.2f) {
			frameTime = 0.2f;
		}

		accumulator += frameTime;
		while (accumulator >= fixedTimestep) {
			fixedUpdate();
			accumulator -= fixedTimestep;
		}

		input();

		update();

		render(accumulator / fixedTimestep);


		glEnable(GL_BLEND);
		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

		glm::vec3 todoPos(10.0f, 20.0f, -0.5f);
		glm::vec4 color(0.0f, 1.0f, 0.0f, 0.5f);
		glm::mat4 mat = glm::ortho(0.0f, (float)WINDOW_WIDTH, (float)WINDOW_HEIGHT, 0.0f, 0.1f, 1.0f);

		std::string str = zen::format("%d frames", SDL::frame.totalFrames);
		glut::drawFont(fontID, str.c_str(), &todoPos[0], &color[0], &mat[0][0]);

		todoPos.y += 20;
		int32_t ms = (int32_t)(1.0e3 * SDL::frame.totalTime / SDL::frame.totalFrames);
		str = zen::format("%d (ms)", ms);
		glut::drawFont(fontID, str.c_str(), &todoPos[0], &color[0], &mat[0][0]);

		glut::renderFrame();
		SDL::endFrame();
	}


	glut::quit();
	SDL::destroyWindow();

	return 0;
}