title: How are Windows VK_ constants declared?
body: <p>For example VK_LEFT, VK_DELETE, VK_ESCAPE, VK_RETURN, etc. How and where are they declared? Are they constants, #defines, or something else? Where do they come from?</p>
  
  <p>If possible, please provide a file name/path where they are declared. Or some other info as specific as possible.</p>