#  PictureShowQt.py  (c) Kari Laitinen

#  http://www.naturalprogramming.com/

#  2009-11-16  File created.
#  2009-11-23  Last modification.

import sys
from PyQt4 import QtGui, QtCore

from threading import Thread
from threading import Event
from time import sleep

##gtk.gdk.threads_init()   # Initializing the gtk's thread engine

class AnimationThread ( Thread ) :

   def __init__( self, given_main_thread_object ) :

      Thread.__init__( self ) 

      self.main_thread_object  =  given_main_thread_object

      self.thread_must_be_stopped  =  Event()

      self.mutex = QtCore.QMutex() # Lisäsin tämän mutta ei auttanut.

      # print " thread init done "

   def stop_this_thread( self ) :

      self.thread_must_be_stopped.set()


   def run( self ) :

      while  not self.thread_must_be_stopped.isSet()  :

         #gtk.gdk.threads_enter()  # Acquiring the gtk global mutex
         self.mutex.lock()

         self.main_thread_object.change_picture_and_redraw()

         self.mutex.unlock()
         #gtk.gdk.threads_leave()  # Releasing the gtk global mutex

         sleep( 3.000 )  # Delay of three seconds.

      # print " run method ends "


 
class PictureShowWindow( QtGui.QWidget ) :

   def __init__( self, parent=None ) :

      QtGui.QWidget.__init__( self, parent )

      self.setGeometry( 100, 100, 800, 600 )
 
      self.setWindowTitle( "SHOWING A SEQUENCE OF PICTURES" )

      picture_file_names  =  ( "yellow_field_by_vincent_van_gogh.jpg",
                               "night_watch_by_rembrandt.jpg",
                               "persistence_of_memory_by_dali.jpg",
                               "demoiselles_de_avignon_by_picasso.jpg",
                               "mona_lisa_by_leonardo.jpg" )

      self.pictures_to_be_shown  =  []

      for  file_name  in  picture_file_names :

         picture_to_be_shown  =  QtGui.QImage( file_name )

         self.pictures_to_be_shown.append( picture_to_be_shown )
                      
      self.index_of_current_picture  =  0

      self.animation_thread  =  AnimationThread( self )
      self.animation_thread.start()

   def change_picture_and_redraw( self ) :

      self.index_of_current_picture  +=  1

      if  self.index_of_current_picture  >=  len( self.pictures_to_be_shown ) :

         self.index_of_current_picture  =  0

      self.repaint()
      #QtGui.QWidget.repaint( self )  # an alternative method call
      # Should I use update() in place of repaint() ???
      #http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qwidget.html#repaint

   def paintEvent( self, event ) :

      painter = QtGui.QPainter()
      
      painter.begin( self )
      
      painter.drawImage( 30, 20,
                  self.pictures_to_be_shown[ self.index_of_current_picture ] )

      painter.end()


   def exit_this_window( self ) :

      self.animation_thread.stop_this_thread()

      self.close() #is this necessary???





#  Here is the main program:

def main( args ) :

   this_application = QtGui.QApplication( args )
   application_window = PictureShowWindow()
   application_window.show()

   # The following statement specifies that when the
   # "lastWindowClosed()" signal is emitted by QApplication,
   # the Python method exit_this_window is called for the
   # PictureShowWindow object.

   this_application.connect( this_application,
                             QtCore.SIGNAL( "lastWindowClosed()" ),
                             application_window.exit_this_window )

   this_application.exec_()
  
if __name__== "__main__" :

   main( sys.argv )

#  Notes:

#  2009-11-23: This program worked in Windows but not in Ubuntu Linux.
#  The Linux error message said that a signal cannot be sent
#  from one thread to another.
#  Must try Qt threads. See ThreadTestQt.py.