#  MovingBallQt.py 

#  http://www.naturalprogramming.com

#  2009-11-18  First program version created by Jaakko Partanen
#  2010-09-27  Last modification by Kari Laitinen

#  This program was transformed to a PyQt application by Jaakko
#  Partanen.

#  Color names used here are described at
#  http://www.w3.org/TR/SVG/types.html#ColorKeywords
#  It should be possible to create QColor objects with these names
#  on all Qt platforms.

import sys

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

class MovingBallWindow( QWidget ) :

   def __init__( self, parent = None ) :
   
      QWidget.__init__( self, parent )

      self.setWindowTitle( "Move the Ball with Buttons" )
      self.setGeometry( 100, 100, 600, 500 )
      
      left_button = QPushButton( "Left", self )
      up_button = QPushButton( "Up", self )
      down_button = QPushButton( "Down", self )
      right_button = QPushButton( "Right" , self )

      self.connect( left_button,
                    SIGNAL( "clicked()" ), self.left_button_clicked )
      self.connect( up_button,
                    SIGNAL( "clicked()" ), self.up_button_clicked )
      self.connect( down_button,
                    SIGNAL( "clicked()" ), self.down_button_clicked )
      self.connect( right_button,
                    SIGNAL( "clicked()" ), self.right_button_clicked )
      
      self.color_selection_combo_box = QComboBox( self )

      # Method addItem() adds a single item to a QComboBox.

      self.color_selection_combo_box.addItem( "red" )

      # With the addItems() method we can add a tuple of items to
      # a QComboBox.

      self.color_selection_combo_box.addItems( ( "orange", "yellow", "blue",
           "magenta", "cyan", "pink", "lightgray" ) )

      self.connect( self.color_selection_combo_box,
                    SIGNAL( "currentIndexChanged(int)" ),
                    self.color_selection_made )

      #  We use the term "Operations Panel" to describe the
      #  layout into which buttons and the combo box will be
      #  inserted.

      operations_panel = QHBoxLayout()

      #  We use the addStretch() method before and after we
      #  add the widgets to the operations panel. This way the
      #  widgets will be centered on the panel.

      operations_panel.addStretch( 1 )
      operations_panel.addWidget( left_button )
      operations_panel.addWidget( up_button )
      operations_panel.addWidget( down_button )
      operations_panel.addWidget( right_button )
      operations_panel.addWidget( self.color_selection_combo_box )
      operations_panel.addStretch( 1 )

      main_vertical_layout = QVBoxLayout()
      main_vertical_layout.addStretch( 1 )
      main_vertical_layout.addLayout( operations_panel )

      self.setLayout( main_vertical_layout )

      self.current_ball_color = QColor( "red" )

      self.ball_center_point_x = self.width() / 2
      self.ball_center_point_y = self.height() / 2

   def left_button_clicked( self ) :
      self.ball_center_point_x = self.ball_center_point_x - 3
      self.update()
      
   def right_button_clicked( self ) :
      self.ball_center_point_x = self.ball_center_point_x + 3
      self.update()
      
   def up_button_clicked( self ) :
      self.ball_center_point_y = self.ball_center_point_y - 3
      self.update()
      
   def down_button_clicked( self ) :
      self.ball_center_point_y = self.ball_center_point_y + 3
      self.update()
      
   def right_button_clicked( self ) :
      self.ball_center_point_x = self.ball_center_point_x + 3
      self.update()
      
   def color_selection_made( self, index ) :
      self.current_ball_color = \
                   QColor( self.color_selection_combo_box.itemText( index ) )
      self.update()
      
   def paintEvent( self, event ) :
   
      painter = QPainter()
      painter.begin( self )
      
      painter.setBrush( self.current_ball_color )

      # drawEllipse() method is used to fill the ball with the current
      # 'brush' color. In addition it draws the outline of the ball
      # with the current 'pen' color which is black.

      painter.drawEllipse( self.ball_center_point_x - 50,
                           self.ball_center_point_y - 50, 100, 100 )

      painter.drawText( 20, 20, "(%d, %d)"  %  \
                        ( self.ball_center_point_x, self.ball_center_point_y ) )
      painter.end()


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