Styjun

I'm starting OpenGL with C, so I started up a CLion project and got started. For reference, I'm on a Mac 10.14.

This is my CMakeLists.txt:

cmake_minimum_required(VERSION 3.10)
project(GLMC C)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_MODULE_PATH /usr/local/lib/cmake)
set(CMAKE_PREFIX_PATH /usr/local/lib/cmake/glfw3)

find_package (PkgConfig REQUIRED)
find_package (OpenGL REQUIRED)
find_package (glfw3 REQUIRED)

include_directories(/usr/local/include glad)
include_directories($GLFW_INCLUDE_DIRS)

find_library(COCOA_LIBRARY Cocoa REQUIRED)
find_library(IOKIT_LIBRARY IOKit REQUIRED)
find_library(COREVID_LIBRARY CoreVideo REQUIRED)

set(CMAKE_C_STANDARD 99)

add_executable(GLMC main.c glad.c)
target_link_libraries (GLMC
 $OPENGL_LIBRARIES
 $COCOA_LIBRARY
 $COREVID_LIBRARY
 $IOKIT_LIBRARY
 $GLFW3_LIBRARY glfw)

And this is my main.c:

#include "glad.h"
#include <GLFW/glfw3.h>
#include "linmath.h"
#include <stdlib.h>
#include <stdio.h>
static const struct

 float x, y;
 float r, g, b;
 vertices[3] =
 
 -0.6f, -0.4f, 1.f, 0.f, 0.f ,
 0.6f, -0.4f, 0.f, 1.f, 0.f ,
 0.f, 0.6f, 0.f, 0.f, 1.f 
 ;
static const char* vertex_shader_text =
 "uniform mat4 MVP;n"
 "attribute vec3 vCol;n"
 "attribute vec2 vPos;n"
 "varying vec3 color;n"
 "void main()n"
 "n"
 " gl_Position = MVP * vec4(vPos, 0.0, 1.0);n"
 " color = vCol;n"
 "n";
static const char* fragment_shader_text =
 "varying vec3 color;n"
 "void main()n"
 "n"
 " gl_FragColor = vec4(color, 1.0);n"
 "n";
static void error_callback(int error, const char* description)

 fprintf(stderr, "Error: %sn", description);

static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)

 if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
 glfwSetWindowShouldClose(window, GLFW_TRUE);

int main(void)

 GLFWwindow* window;
 GLuint vertex_buffer, vertex_shader, fragment_shader, program;
 GLint mvp_location, vpos_location, vcol_location;
 glfwSetErrorCallback(error_callback);
 if (!glfwInit())
 exit(EXIT_FAILURE);
 glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
 glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
 window = glfwCreateWindow(640, 480, "Simple example", NULL, NULL);
 if (!window)
 
 glfwTerminate();
 exit(EXIT_FAILURE);
 
 glfwSetKeyCallback(window, key_callback);
 glfwMakeContextCurrent(window);
 gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);
 glfwSwapInterval(1);
 // NOTE: OpenGL error checks have been omitted for brevity
 glGenBuffers(1, &vertex_buffer);
 glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
 glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
 vertex_shader = glCreateShader(GL_VERTEX_SHADER);
 glShaderSource(vertex_shader, 1, &vertex_shader_text, NULL);
 glCompileShader(vertex_shader);
 fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
 glShaderSource(fragment_shader, 1, &fragment_shader_text, NULL);
 glCompileShader(fragment_shader);
 program = glCreateProgram();
 glAttachShader(program, vertex_shader);
 glAttachShader(program, fragment_shader);
 glLinkProgram(program);
 mvp_location = glGetUniformLocation(program, "MVP");
 vpos_location = glGetAttribLocation(program, "vPos");
 vcol_location = glGetAttribLocation(program, "vCol");
 glEnableVertexAttribArray(vpos_location);
 glVertexAttribPointer(vpos_location, 2, GL_FLOAT, GL_FALSE,
 sizeof(float) * 5, (void*) 0);
 glEnableVertexAttribArray(vcol_location);
 glVertexAttribPointer(vcol_location, 3, GL_FLOAT, GL_FALSE,
 sizeof(float) * 5, (void*) (sizeof(float) * 2));
 while (!glfwWindowShouldClose(window))
 
 float ratio;
 int width, height;
 mat4x4 m, p, mvp;
 glfwGetFramebufferSize(window, &width, &height);
 ratio = width / (float) height;
 glViewport(0, 0, width, height);
 glClearColor(1,1,1,1);
 glClear(GL_COLOR_BUFFER_BIT);
 mat4x4_identity(m);
 mat4x4_rotate_Z(m, m, (float) glfwGetTime());
 mat4x4_ortho(p, -ratio, ratio, -1.f, 1.f, 1.f, -1.f);
 mat4x4_mul(mvp, p, m);
 glUseProgram(program);
 glUniformMatrix4fv(mvp_location, 1, GL_FALSE, (const GLfloat*) mvp);
 glDrawArrays(GL_TRIANGLES, 0, 3);
 glfwSwapBuffers(window);
 glfwPollEvents();
 
 glfwDestroyWindow(window);
 glfwTerminate();
 exit(EXIT_SUCCESS);

This is the sample code on their website.
I have this basic GLFW/GLAD code. The latest versions of glad.h, glad.c and khrplatform.h are properly referenced.

I have installed glfw3 through brew properly, and succesfully referenced it through C++ and XCode, but I wanted to do it in C and CLion.

The window is entirely black, until it is moved by dragging the title bar, which causes everything to work perfectly.

Turns out, this is a known bug on Mac Mojave. I fixed this by setting the window position (simulating a window drag) on the first iteration of the main loop:

bool hasWindowBeenFixed=false;

while(true)
 glfwSwapBuffers(); // IMPORTANT: The fix only works AFTER swap buffers has been called
 if(!hasWindowBeenFixed)
 hasWindowBeenFixed=true;
 glfwSetWindowPos(window,50,50);