gameoflife/opengl_train.c

#include <GL/glew.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>
#include <stdbool.h>
#include <stdio.h>

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

#define FACTOR 80
#define WIDTH ((FACTOR) * 16)
#define HEIGHT ((FACTOR) * 9)

SDL_Event e;

float vertices[] = {
	// Positions	Color				TexCoords
    -0.5f,  0.5f,	1.0f, 0.0f, 0.0f,	0.0f, 0.0f, // Top-left
     0.5f,  0.5f,	0.0f, 1.0f, 0.0f,	1.0f, 0.0f, // Top-right
     0.5f, -0.5f,	0.0f, 0.0f, 1.0f,	1.0f, 1.0f, // Bottom-right
    -0.5f, -0.5f,	1.0f, 1.0f, 1.0f,	0.0f, 1.0f, // Bottom-left
};

GLuint elements[] = {
	0, 1, 2,
	2, 3, 0,
};

char * read_file(const char* path){
	FILE* file = fopen(path, "r");

	fseek(file, 0, SEEK_END);
	int eof = ftell(file);
	fseek(file, 0, SEEK_SET);

	char* file_content = malloc(eof * sizeof(char));
	fread(file_content, sizeof(char), eof, file);
	fclose(file);
	return file_content;
}

GLuint CompileShader(const char* data, GLenum type){
	GLuint shader = glCreateShader(type);
	glShaderSource(shader, 1, &data, NULL);
	glCompileShader(shader);

	GLint status;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
	char buffer[512];
	glGetShaderInfoLog(shader, 512, NULL, buffer);
	printf("%s", buffer);

	return shader;
}

GLuint LinkShader(GLuint vertexShader, GLuint fragmentShader){
	GLuint shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	GLint status;
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &status);
	char buffer[512];
	glGetProgramInfoLog(shaderProgram, 512, NULL, buffer);
	printf("%s", buffer);

	return shaderProgram;
}

int main(void)
{

	const char* vs = read_file("./shader.vs");
	const char* fs = read_file("./shader.fs");

	if(SDL_Init(SDL_INIT_EVENTS | SDL_INIT_VIDEO)){
		SDL_Log("Unable to initialize SDL: %s", SDL_GetError());
	}

	SDL_Window *win;

	win = SDL_CreateWindow("Game of life", 0, 0, WIDTH, HEIGHT, SDL_WINDOW_OPENGL);
	if(!win){
		SDL_Log("Unable to create Window: %s", SDL_GetError());
	}
	SDL_GLContext con = SDL_GL_CreateContext(win);
	if(!con){
		SDL_Log("Unable to create OpenGL Context: %s", SDL_GetError());
	}

	if(glewInit()){
		SDL_Log("SDL_INIT error");
	};

	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

	// vectors
	GLuint vertexBuffer;
	glGenBuffers(1, &vertexBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);

	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	// reuse vectors
	GLuint ebo;
	glGenBuffers(1, &ebo);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

	GLuint vertexShader = CompileShader(vs, GL_VERTEX_SHADER);
	GLuint fragmentShader = CompileShader(fs, GL_FRAGMENT_SHADER);
	GLuint shaderProgram = LinkShader(vertexShader, fragmentShader);

	// Textures
	int width, height;
	unsigned char *image, *image2;

	GLuint tex[2];
	glGenTextures(2, tex);

	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, tex[0]);

	//Load image
	image = stbi_load("./sample.png", &width, &height, NULL, 3);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
	stbi_image_free(image);
	glGenerateMipmap(GL_TEXTURE_2D);

	glUniform1i(glGetUniformLocation(shaderProgram, "kitty"), 0);

	glActiveTexture(GL_TEXTURE1);
	glBindTexture(GL_TEXTURE_2D, tex[1]);

	//Load image
	image2 = stbi_load("./sample2.png", &width, &height, NULL, 3);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image2);
	stbi_image_free(image2);
	glGenerateMipmap(GL_TEXTURE_2D);

	glUniform1i(glGetUniformLocation(shaderProgram, "puppy"), 1);

	GLint posAttrib = glGetAttribLocation(shaderProgram, "positions");
	glEnableVertexAttribArray(posAttrib);
	glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 7, 0);

	GLint colAttrib = glGetAttribLocation(shaderProgram, "color");
	glEnableVertexAttribArray(colAttrib);
	glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 7, (void*)(2*sizeof(float)));

	GLint texCoordsAttrib = glGetAttribLocation(shaderProgram, "texCoords");
	glEnableVertexAttribArray(texCoordsAttrib);
	glVertexAttribPointer(texCoordsAttrib, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 7, (void*)(5*sizeof(float)));

	glUseProgram(shaderProgram);

	int i = 0;
	bool should_close = false;
	while(!should_close){
		i++;
		glClearColor(0, 0, 0, 1);
		glClear(GL_COLOR_BUFFER_BIT);
		glUniform1i(glGetUniformLocation(shaderProgram, "triangleColor"), i);

		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		/* glDrawArrays(GL_TRIANGLES, 0, 3); */

		SDL_GL_SwapWindow(win);

		while(SDL_PollEvent(&e)){
			if(e.type == SDL_QUIT) should_close = true;
			if(e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_a) should_close = true;
		}
	}

	glDeleteProgram(shaderProgram);
	glDeleteShader(fragmentShader);
	glDeleteShader(vertexShader);

	SDL_GL_DeleteContext(con);
	SDL_DestroyWindow(win);
	SDL_Quit();

	return 0;
}