title: Preprocessor-IF doesn't work
body: <p>I'm trying to check with Preprocessor-Ifs if the Device is an iPad. If it is an iPad, I want to define something Devicespecific, but for some reason I can't check in an PP-IF if a PP-Constant is true.</p>
  
  <p>Maybe you got an idea?</p>
  
  <pre><code>#ifdef UI_USER_INTERFACE_IDIOM
  
      #define IS_IPAD (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad)
  
  #else
  
      #define IS_IPAD false
  
  #endif
  
  
  
  #if IS_IPAD
  
      #define WIDTH 768
      #define HEIGHT 1024
  
  #else
  
      #define WIDTH 320
      #define HEIGHT 480
  
  #endif
  </code></pre>