Function init_webgl

test/minimal_webgl/webgl.c:45–100

}

void init_webgl(int width, int height)
{
  double dpr = emscripten_get_device_pixel_ratio();
  emscripten_set_element_css_size("canvas", width / dpr, height / dpr);
  emscripten_set_canvas_element_size("canvas", width, height);

  EmscriptenWebGLContextAttributes attrs;
  emscripten_webgl_init_context_attributes(&attrs);
  attrs.alpha = 0;
#if MAX_WEBGL_VERSION >= 2
  attrs.majorVersion = 2;
#endif
  glContext = emscripten_webgl_create_context("canvas", &attrs);
  assert(glContext);
  emscripten_webgl_make_context_current(glContext);

  pixelWidth = 2.f / width;
  pixelHeight = 2.f / height;

  static const char vertex_shader[] =
    "attribute vec4 pos;"
    "varying vec2 uv;"
    "uniform mat4 mat;"
    "void main(){"
      "uv=pos.xy;"
      "gl_Position=mat*pos;"
    "}";
  GLuint vs = compile_shader(GL_VERTEX_SHADER, vertex_shader);

  static const char fragment_shader[] =
    "precision lowp float;"
    "uniform sampler2D tex;"
    "varying vec2 uv;"
    "uniform vec4 color;"
    "void main(){"
      "gl_FragColor=color*texture2D(tex,uv);"
    "}";
  GLuint fs = compile_shader(GL_FRAGMENT_SHADER, fragment_shader);

  GLuint program = create_program(vs, fs);
  colorPos = glGetUniformLocation(program, "color");
  matPos = glGetUniformLocation(program, "mat");
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

  glGenBuffers(1, &quad);
  glBindBuffer(GL_ARRAY_BUFFER, quad);
  const float pos[] = { 0, 0, 1, 0, 0, 1, 1, 1 };
  glBufferData(GL_ARRAY_BUFFER, sizeof(pos), pos, GL_STATIC_DRAW);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
  glEnableVertexAttribArray(0);

  solidColor = create_texture();
  unsigned int whitePixel = 0xFFFFFFFFu;
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 1, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, &whitePixel);
}

typedef void (*tick_func)(double t, double dt);