title: source_group CMake command isn't working
body: <p>I don't understand the source_group command in my CMakeLists.txt.
  When I do this it works:</p>
  
  <pre><code>file(GLOB INPUT_HEAD    KeyBoard.h Mouse.h)
  source_group("Header Files\\Input" FILES ${INPUT_HEAD})
  </code></pre>
  
  <p>But this isn't working:</p>
  
  <pre><code>file(GLOB SHADERS ../Shaders/*.txt)
  source_group("Source Files\\Shaders" FILES ${SHADERS})
  </code></pre>
  
  <p>Any suggestions on how to solve this?
  (I have read the documentation for this command, I don't understand whythis doesn't work)</p>