gl-util.c

#include <stdlib.h>
#include <GL/glew.h>
#ifdef __APPLE__
#  include <GLUT/glut.h>
#else
#  include <GL/glut.h>
#endif
#include <stddef.h>
#include <math.h>
#include <stdio.h>
#include "file-util.h"

GLuint make_texture(const char *filename)
{
    int width, height;
    void *pixels = read_tga(filename, &width, &height);
    GLuint texture;

    if (!pixels)
        return 0;

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,     GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,     GL_CLAMP_TO_EDGE);
    glTexImage2D(
        GL_TEXTURE_2D, 0,           /* target, level */
        GL_RGB8,                    /* internal format */
        width, height, 0,           /* width, height, border */
        GL_BGR, GL_UNSIGNED_BYTE,   /* external format, type */
        pixels                      /* pixels */
    );
    free(pixels);
    return texture;
}

void show_info_log(
    GLuint object,
    PFNGLGETSHADERIVPROC glGet__iv,
    PFNGLGETSHADERINFOLOGPROC glGet__InfoLog
)
{
    GLint log_length;
    char *log;

    glGet__iv(object, GL_INFO_LOG_LENGTH, &log_length);
    log = malloc(log_length);
    glGet__InfoLog(object, log_length, NULL, log);
    fprintf(stderr, "%s", log);
    free(log);
}

GLuint make_shader(GLenum type, const char *filename)
{
    GLint length;
    GLchar *source = file_contents(filename, &length);
    GLuint shader;
    GLint shader_ok;

    if (!source)
        return 0;

    shader = glCreateShader(type);
    glShaderSource(shader, 1, (const GLchar**)&source, &length);
    free(source);
    glCompileShader(shader);

    glGetShaderiv(shader, GL_COMPILE_STATUS, &shader_ok);
    if (!shader_ok) {
        fprintf(stderr, "Failed to compile %s:\n", filename);
        show_info_log(shader, glGetShaderiv, glGetShaderInfoLog);
        glDeleteShader(shader);
        return 0;
    }
    return shader;
}

GLuint make_program(GLuint vertex_shader, GLuint fragment_shader)
{
    GLint program_ok;

    GLuint program = glCreateProgram();

    glAttachShader(program, vertex_shader);
    glAttachShader(program, fragment_shader);
    glLinkProgram(program);

    glGetProgramiv(program, GL_LINK_STATUS, &program_ok);
    if (!program_ok) {
        fprintf(stderr, "Failed to link shader program:\n");
        show_info_log(program, glGetProgramiv, glGetProgramInfoLog);
        glDeleteProgram(program);
        return 0;
    }
    return program;
}