#  MovingBallWithMouseQt.py  Copyright (c) Kari Laitinen

#  http://www.naturalprogramming.com

#  2010-09-28  File created.
#  2010-09-28  Last modification.

#  This program draws three Ball objects onto the screen.
#  It is possible to move these balls by dragging them with
#  the mouse. The Ball class provides a method with which it is
#  possible to find out whether a clicked point is inside the
#  ball. In addition the Ball class provides methods for moving
#  the ball.

#  During compilation/execution the file BallQt.py must be in the same
#  folder (directory) with this file.


import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

from BallQt import Ball

class MovingBallWithMouseWindow( QWidget ) :

   def __init__( self, parent = None ) :

      QWidget.__init__( self, parent )

      self.setGeometry( 200, 200, 680, 480 )

      self.setWindowTitle( "MOVE THE BALLS WITH THE MOUSE" )

      window_width   =  self.width()
      window_height  =  self.height()

      #  The coordinates that are given to Ball constructor refer to
      #  the center point of a ball.

      self.first_ball   =  Ball( window_width / 2  -  120,
                                 window_height / 2,  Qt.red )

      self.second_ball  =  Ball( window_width / 2,
                                 window_height / 2,  Qt.green )

      self.third_ball   =  Ball( window_width / 2  + 120,
                                 window_height / 2,  Qt.blue )

      self.ball_being_moved  =  None

      self.previous_cursor_position_x  =  0 
      self.previous_cursor_position_y  =  0


   def mousePressEvent( self, event ) :

      cursor_position_x = event.x()
      cursor_position_y = event.y()

      if  self.first_ball.contains_point( cursor_position_x,
                                          cursor_position_y ) :

         self.ball_being_moved  =  self.first_ball
         self.ball_being_moved.activate_ball()

      elif  self.second_ball.contains_point( cursor_position_x,
                                             cursor_position_y ) :

         self.ball_being_moved  =  self.second_ball
         self.ball_being_moved.activate_ball()

      elif  self.third_ball.contains_point( cursor_position_x,
                                            cursor_position_y ) :

         self.ball_being_moved  =  self.third_ball
         self.ball_being_moved.activate_ball()


      self.previous_cursor_position_x  =  cursor_position_x
      self.previous_cursor_position_y  =  cursor_position_y

      self.update()


   def mouseMoveEvent( self, event ) :

      if  self.ball_being_moved  !=  None :

         new_cursor_position_x = event.x()
         new_cursor_position_y = event.y()
    
         mouse_movement_x  =  int( new_cursor_position_x )  \
                                   -  self.previous_cursor_position_x
         mouse_movement_y  =  int( new_cursor_position_y )  \
                                   -  self.previous_cursor_position_y

         self.previous_cursor_position_x  =  int( new_cursor_position_x )
         self.previous_cursor_position_y  =  int( new_cursor_position_y )

         self.ball_being_moved.move_this_ball( mouse_movement_x,
                                               mouse_movement_y )
         self.update()


   def mouseReleaseEvent( self, event ) :

      if  self.ball_being_moved  !=  None :

         self.ball_being_moved.deactivate_ball()
         self.ball_being_moved  =  None
         self.update()


   def paintEvent( self, event ) :

      painter = QPainter()

      painter.begin( self )

      self.first_ball.draw( painter )
      self.second_ball.draw( painter )
      self.third_ball.draw( painter )

      painter.end()


#  The main program begins.

this_application = QApplication( sys.argv )
application_window = MovingBallWithMouseWindow()
application_window.show()
this_application.exec_()