title: gtk, how to ask the window manager to activate the main window
body: <p>I help maintain Xournal. One feature we support is making a screenshot.
  We do this by activating the root window and then taking a screenshot.</p>
  
  <p>The issue that I am having is that after the screenshot is made, the active window remains the root window. How do I ask gtk to make the main window of xournal the active one?</p>
  
  <p>I have used gtk_widget_grab_focus but that does not seem to work.</p>
  
  <p>thank you.</p>
  
  <p>--daniel</p>