title: Is there a function in gtkmm that reads from FileInputStream in the way that can then be used to set the TextArea
body: <p>I'm trying to read text from file and put it in the TextView. <a href="https://developer.gnome.org/glibmm/unstable/classGio_1_1FileInputStream.html" rel="nofollow">FileInputStream</a> has <code>read_bytes</code>, there is <code>set_text</code> in <a href="https://developer.gnome.org/gtkmm/stable/classGtk_1_1TextBuffer.html" rel="nofollow">TextBuffer</a> that can take <code>ustring</code>, but there seem to be no way to go from one to another.</p>
  
  <p>In the InputStream's child classes i found <a href="https://developer.gnome.org/glibmm/unstable/classGio_1_1DataInputStream.html" rel="nofollow">DataInputStream</a> which does have <code>read_line_utf8</code> giving one an std::string (better than nothing), but even DataInputStream is on the separate class hierarchy branch from FileInputStream.</p>
  
  <p>Of course, theoretically it is possible to just cycle through the array of bytes returned by the <code>read_bytes</code> and turn them into characters, but somehow i just refuse to believe that there is no ready function that i'm overlooking.</p>
  
  <p>Ultimately i'm looking for a function that would take <code>Glib::RefPtr&lt;Glib::Bytes&gt;</code> and return me a <code>Glib::ustring</code></p>