Index

1. Lecture: 16-1

• Prerequisites for this lecture are: 15-1, 15-2 and 15-3.

2. Implementation of Touchmap

• these notes will show the structure of touchmap.py
• they also will describe touchgui.select
• they will show you how extend touchmap
  • creating an export function
  • create a worldspawn entity
• also show you how to add your own graphics into the library
• touchmap is implemented in a single file
• uses a similar structure to the demo programs in touchgui

• touchmap-0.1/touchmap.py

  def main ():
      global players, grid, cell_size
  
      pygame.init ()
      if full_screen:
          gameDisplay = pygame.display.set_mode ((display_width, \
                                               display_height), FULLSCREEN)
      else:
          gameDisplay = pygame.display.set_mode ((display_width, display_height))
  
      touchgui.set_display (gameDisplay, display_width, display_height)
      controls = buttons ()
  
      gameDisplay.fill (touchguipalate.black)
      while True:
          grid = button_grid (cell_size)
          forms = controls + grid
          touchgui.select (forms, event_test, finished)
  
  main ()

3. touchgui.select

• touchgui/touchgui.py

  def select (forms, event_test, finished = None, timeout = -1):
      if timeout == -1:
          _blocking_select (forms, event_test, finished)
      else:
          _nonblocking_select (forms, event_test, finished, timeout)

• two optional parameters: finished and timeout
• if timeout is absent then it calls a blocking version of select
  • in which the process will block until an event occurs
  • this is efficient, but forces the main program to be entirely event based
    • furthermore all events must go through the touchgui/pygame event queue
• sometimes you might want to write programs which use a mixture of event based and some polling
• for example the cluedo server program
  • tests the gui briefly and then checks the network stack for input and rotates icons
    • ideally it would be good to join the network stack to the pygame input event queue and timers
    • in practice this is hard to configure, and touchgui.select allows a pragmatic (less efficient) solution
    • can poll both
      

4. Cluedo server example code

•     offset = 0
      while not selection_complete:
          s, rpc = getRPC (s)
          processRPC (s, rpc)
          playerIcons = positionIcons (players, [.5, .5], .2, offset)
          forms = playerIcons + playerIconsStatic
          gameDisplay.fill (palate.black)
          touchgui.select (forms, event_test, selected, 10)
          offset = (offset + 1) % 360
      return players

5. touchgui.select

• redraws all tiles in forms.
• finished is polled to see if the function should return
  • finished is a parameterless function which returns True or False
• timeout is the maximum no. of milliseconds the function can poll.
  • timeout is optional and defaults to -1 if absent
• finished is also optional
• Pre-condition
  • forms is a list of tiles.
  • event_test is which has a single parameter (event)
  • event_test does not return a value
• Post-condition: None.

Index

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