title: Understanding the location of ui_mainwindow.h in the Qt Creater widgets template
body: <p>I am writing my first application with Qt Creator, and I have loaded the default widget template. In <code>mainwindow.cpp</code>, there is the line <code>#include "ui_mainwindow.h"</code>. However, this file does not exist yet. After compiling the code, I notice that there is a filed named <code>ui_mainwindow.h</code> in the build folder.</p>
  
  <p>Please could somebody explain what is going on here? It seems that perhaps there is a two-stage build process, one to build the user interface files (i.e. <code>ui_mainwindow.h</code>), and then one to build the actual program. In that case, and if this header file is put in the build directory, why is it <code>#include "ui_mainwindow.h"</code> rather than <code>#include "../build/ui_mainwindow.h"</code>?</p>