title: How to fix my deprecated use of gluOrtho2D()?
body: <p>I've got existing code (OS X, Obj-C, NSOpenGLView) that calls:</p>
  
  <pre><code>gluOrtho2D(0.0, newSize.width, newSize.height, 0.0);
  </code></pre>
  
  <p>It works fine except that I get a deprecated function warning that urges me to use GLKMatrix4MakeOrtho() instead.  OK – but how?  I can't seem to even find the existence of that function; I'm including:</p>
  
  <pre><code>#import &lt;OpenGL/gl.h&gt;
  #import &lt;OpenGL/glu.h&gt;
  </code></pre>
  
  <p>and Xcode does not know of a function by that name.  My OpenGL reference manual does not have any mention of it, or indeed, of any functions with the prefix GLK; what's going on there?  And then if I managed to find the function and include the right header and link against whatever I need to link against, what then – what would an equivalent call be for GLKMatrix4MakeOrtho() that would do the same thing as my gluOrtho2D() call?  I tried Googling, and found many hits showing that other people are getting the same deprecation warning, but I couldn't find anybody saying how to fix it...</p>