#  EarthAndMoonGTK.py  (c) Kari Laitinen

#  http://www.naturalprogramming.com

#  2009-04-15  File created.
#  2009-04-15  Last modification.

#  This program shows, among other things, how texts can be drawn
#  with different fonts.

#  More notes at the end of this file.

import gtk
import pango

class EarthAndMoon :

   def __init__( self ) :

      self.application_window = gtk.Window( gtk.WINDOW_TOPLEVEL )
      self.application_window.set_title( "BALLS DEPICTING EARTH AND MOON" )
      self.application_window.connect("destroy", lambda w: gtk.main_quit() )

      self.application_window.set_size_request( 600, 400 )
      self.drawing_area = gtk.DrawingArea()

      self.application_window.add( self.drawing_area )

      self.drawing_area.connect( "expose-event", self.drawing_area_exposed )

      self.application_window.show_all()

      self.large_font_description   = pango.FontDescription( "serif bold 20" )
      self.italic_font_description  = pango.FontDescription( "serif italic 12" )
      self.bold_italic_font_description  =  \
                                 pango.FontDescription( "serif bold italic 10" )

   def drawing_area_exposed( self, area, event ) :

      graphics_context = self.drawing_area.get_style().fg_gc[gtk.STATE_NORMAL]

      this_drawable  =  self.drawing_area.window

      window_width, window_height  =  self.application_window.get_size()

      graphics_context.foreground  =  \
                  this_drawable.get_colormap().alloc_color( "green" )

      this_drawable.draw_arc( graphics_context, True,
                              30, 30, 212, 212, 0, 360*64 )  #  Earth

      graphics_context.foreground  =  \
                  this_drawable.get_colormap().alloc_color( "blue" )

      this_drawable.draw_arc( graphics_context, True,
                              400, 100, 58, 58, 0, 360*64 )  #  Moon


      graphics_context.foreground  =  \
                  this_drawable.get_colormap().alloc_color( "black" )

      text_to_show  =  self.drawing_area.create_pango_layout( "" )

      text_to_show.set_font_description( self.large_font_description )
      text_to_show.set_text( "Earth" )
      this_drawable.draw_layout( graphics_context, 100, 270, text_to_show )
      text_to_show.set_text( "Moon" )
      this_drawable.draw_layout( graphics_context, 400, 190, text_to_show )

      text_to_show.set_font_description( self.italic_font_description )
      text_to_show.set_text( "Equatorial radius: 6380 km, 3960 miles" )
      this_drawable.draw_layout( graphics_context,  30, 300, text_to_show )
      text_to_show.set_text( "Radius: 1740 km, 1080 miles" )
      this_drawable.draw_layout( graphics_context, 350, 220, text_to_show )

      text_to_show.set_font_description( self.bold_italic_font_description )
      text_to_show.set_text( "Mean distance between Earth and Moon is" )
      this_drawable.draw_layout( graphics_context, 200, 330, text_to_show )
      text_to_show.set_text( "384 400 kilometers, 238 860 miles" )
      this_drawable.draw_layout( graphics_context, 200, 345, text_to_show )

      return True

   def run( self ) :
      gtk.main()

if __name__ == "__main__":
   this_application  =  EarthAndMoon()
   this_application.run()


#  NOTES

#  In PyGTK, fonts can be specified as pango.FontDescription objects.
#  See http://www.pygtk.org/pygtk2reference/class-pangofontdescription.html

#  The fonts, in general, are a quite mysterious thing in the world of
#  computing. Different computers use different fonts. For this reason,
#  the output of this program may not be the same in every computer.

#  In this program, texts are drawn as pango.Layout objects.
#  The upper left corner of the text object is specified as parameters for
#  the drawing method.

#  This program has been tested in Ubuntu Linux. In general it seems
#  that when you define in Linux a font of a certain size, the font that will
#  be seen on the screen is larger than, for example, the same text size
#  in Windows.