Revision as of 10:32, 17 September 2012

Brick-Breaker is a simple arcade game where the player moves a paddle on the screen and bounces a ball towards bricks at the top of the screen. When the ball hits a brick it breaks and the ball bounces back - the objective of the game is to destroy all the bricks. This is the first article explaining the PySymbian implementation of Brick-Breaker - it covers the different slider functions in detail.

02 Aug
2009

Development tools

1. Text editor - notepad is sufficient.
2. PySymbian - preferred version: PySymbian 1.4.5 stable release
3. PySymbian script shell - preferred version: PySymbian 1.4.5 stable release

The PySymbian tools can be downloaded from Sourceforge resources.

The following modules are used when developing this application:

• appuifw module
• sysinfo module
• graphics module
• e32 module
• key_codes module
• random module
• math module
• time module

Functions

The following functions are used in Brick Breaker game.

1. draw_screen: draw black screen in canvas.
2. draw_slider: draw slider.
3. leftkey: control the slider by left key.
4. rightkey: control the slider by right key.
5. draw_bricks: draw number of bricks.
6. erase_bricks: erase bricks.

Initializing slider parameter

Before discussing, any functions in detail - let us define some of the slider parameters.

#SLIDER PARAMETERS#####
 
SliderX1=120
SliderY1=305
SliderX2=160
SliderY2=315
SliderSpeed=22
 
SliderColor=RED
 
import sysinfo
TotalScreenWidth=sysinfo.display_pixels()[1]

draw_screen()

By using this function, We create a black screen in canvas. The definition of the draw_screen() is as follows:

#defining draw function
def draw_screen():
       #Set the screen to full
       appuifw.app.screen = 'full'
 
       #Global variable for application UI 
       global canvas
       canvas = appuifw.Canvas(redraw_callback=handle_redraw)    
       appuifw.app.body = canvas
       appuifw.app.exit_key_handler = quit
 
       #Global variable for application UI
       global img
       img = graphics.Image.new(canvas.size)
 
       #Clear the image
       img.clear(BLACK)
       handle_redraw(None)

draw_slider()

By using this function, we create a slider in canvas using keyboard shortcuts. The definition of the draw_screen() is as follows:

#defining slider function
def draw_slider():
	global canvas
 
	#Keyboard shortcuts
	canvas.bind(key_codes.EKeyLeftArrow,lambda:  leftkey())
	canvas.bind(key_codes.EKeyRightArrow,lambda: rightkey())
	appuifw.app.body = canvas
	appuifw.app.exit_key_handler = quit
 
       #draw the rectangle	
	img.rectangle((SliderX1,SliderY1,SliderX2,SliderY2),fill=SliderColor)   
	handle_redraw(None)

leftkey()

The leftkey() is called from the draw_slider() function. By using this function, we can move the slider to left side by pressing left key. Thus, the code of leftkey() function is as follows:

#defining leftkey function
def leftkey():
	if (SliderX1>0):
               #draw the rectangle
		img.rectangle((SliderX1, SliderY1, SliderX2, SliderY2),fill=BLACK)
 
               #globally define variables    
		global img, canvas,SliderX1, SliderY1, SliderX2, SliderY2
 
               #defining the slider coordinate X1 and X2
		SliderX1=SliderX1-SliderSpeed
		SliderX2=SliderX2-SliderSpeed
		img.rectangle((SliderX1, SliderY1, SliderX2, SliderY2),fill=SliderColor)
 
	       #appuifw.note(u"Left arrow was pressed")
		handle_redraw(None)

rightkey()

The rightkey() is called from the draw_slider() function. By using this function, we can move the slider to right side by pressing right key. Thus the code of rightkey() function is as follows:

#defining right key function
def rightkey():
	if (SliderX2<TotalScreenWidth):
	#if (SliderX2<sysinfo.display_pixels()[1]):
                #draw rectangle
		 img.rectangle((SliderX1, SliderY1, SliderX2, SliderY2),fill=BLACK)
 
                #globally define variables    
		 global img, canvas,SliderX1, SliderY1, SliderX2, SliderY2
 
               #defining the slider coordinate X1 and X2
		SliderX1=SliderX1+SliderSpeed
		SliderX2=SliderX2+SliderSpeed
		img.rectangle((SliderX1, SliderY1, SliderX2, SliderY2),fill=SliderColor)
 
		#appuifw.note(u"Left arrow was pressed")
		 handle_redraw(None)

That finishes the slider functions (Part 1) for the Brick-Breaker Game.

The next article in the series : Part 2 for brick-Breaker, would cover Brick functions for this game.

Screenshots

These screenshots demonstrate the Slider and its movable position on canvas. The screenshots are relevant only to Part 1.

Related Links

• How to develop brick-breaker game in PySymbian - Part 2
• How to develop brick-breaker game in PySymbian - Part 3
• Introduction to PySymbian