opengl_test.cr

if LibGLFW3.init != 0
error_callback = ->(error : Int32, description : Int8*) {
  puts "Error #{error}: #{String.new(description.as(UInt8*))}"
}
LibGLFW3.setErrorCallback(error_callback)

LibGLFW3.windowHint(LibGLFW3::OPENGL_PROFILE, LibGLFW3::OPENGL_CORE_PROFILE)
LibGLFW3.windowHint(LibGLFW3::OPENGL_FORWARD_COMPAT, 1)
LibGLFW3.windowHint(LibGLFW3::CONTEXT_VERSION_MAJOR, 4)
LibGLFW3.windowHint(LibGLFW3::CONTEXT_VERSION_MINOR, 2)
LibGLFW3.windowHint(LibGLFW3::OPENGL_DEBUG_CONTEXT, 1)

window = LibGLFW3.createWindow(800, 600, "Hello Crystal!", nil, nil)

if window
  LibGLFW3.makeContextCurrent(window)
  LibGLFW3.swapInterval(1)

  points = [
    0.0f32,  0.5f32,  0.0f32,
    0.5f32, -0.5f32,  0.0f32,
   -0.5f32, -0.5f32,  0.0f32
  ]

  LibGL.genBuffers 1, out vbo
  LibGL.bindBuffer LibGL::ARRAY_BUFFER, vbo
  LibGL.bufferData LibGL::ARRAY_BUFFER, 9 * sizeof(Float32), points, LibGL::STATIC_DRAW

  LibGL.genVertexArrays 1, out vao
  LibGL.bindVertexArray vao
  LibGL.bindBuffer LibGL::ARRAY_BUFFER, vbo
  LibGL.vertexAttribPointer 0, 3, LibGL::FLOAT, LibGL::FALSE, 0, nil

  vertex_shader = ["#version 420\nin vec3 vp; void main() { gl_Position = vec4(vp, 1.0); }".to_unsafe.as(Int8*)]
  fragment_shader = ["#version 420\nout vec4 frag_color; void main() { frag_color = vec4(0.5, 0.0, 0.5, 1.0); }".to_unsafe.as(Int8*)]
  vs_pp = vertex_shader.to_unsafe
  fs_pp = fragment_shader.to_unsafe

  vs = LibGL.createShader(LibGL::VERTEX_SHADER);
  LibGL.shaderSource(vs, 1, vs_pp, nil);
  LibGL.compileShader(vs);
  fs = LibGL.createShader(LibGL::FRAGMENT_SHADER);
  LibGL.shaderSource(fs, 1, fs_pp, nil);
  LibGL.compileShader(fs);

  LibGL.getShaderiv vs, LibGL::COMPILE_STATUS, out status1
  LibGL.getShaderiv fs, LibGL::COMPILE_STATUS, out status2
  pp status1, status2

  shader_programme = LibGL.createProgram();
  LibGL.attachShader(shader_programme, fs);
  LibGL.attachShader(shader_programme, vs);
  LibGL.linkProgram(shader_programme);

  while (error = LibGL.getError) != LibGL::NO_ERROR
   p error
  end

  while LibGLFW3.windowShouldClose(window) == 0
    LibGLFW3.getFramebufferSize(window, out width, out height)
    ratio = width.to_f / height.to_f

    LibGL.viewport(0, 0, width, height);
    LibGL.clear(LibGL::COLOR_BUFFER_BIT | LibGL::DEPTH_BUFFER_BIT);

    LibGL.useProgram shader_programme
    
    LibGL.bindVertexArray vao
    LibGL.drawArrays LibGL::TRIANGLES, 0, 3

    while (error = LibGL.getError) != LibGL::NO_ERROR
      puts error
    end
    
    LibGLFW3.swapBuffers(window)
    LibGLFW3.pollEvents
  end

  LibGLFW3.destroyWindow(window)
else
  puts "Failed to create window"
end

LibGLFW3.terminate
else
puts "GLFW failed to initialize"
end