Now calling move for a ball computes the next position of the ball for the next frame.

3 files changed, 40 insertions, 32 deletions

diff --git a/ball.py b/ball.py
index 21b5e09..01a0fdf 100644
--- a/ball.py
+++ b/ball.py
@@ -4,7 +4,7 @@ Created on Sat Sep 14 10:57:17 2013
 
 @author: laurent-bernabe
 """
-
+import pygame
 
 class Ball(object):
 
@@ -12,19 +12,23 @@ class Ball(object):
     An abstractation of a ball.
     """
 
-    def __init__(self, txt_font, txt_color, bg_color, operation):
+    def __init__(self, txt_font, txt_color, bg_color, operation, velocity):
         """
         Constructor
         txt_font : text font => olpcgames.pangofont
         txt_color : text color => Tuple of 3 integers in [0,255]
         bg_color : background color => Tuple of 3 integers in [0,255]
         operation : operation => An Operation value
+        velocity : current direction of move => A tuple of 2 floats (x,y)
         """
+        info = pygame.display.Info()
+        self._SCREEN_WIDTH, self._SCREEN_HEIGTH = info.current_w, info.current_h        
         self._txt_font = txt_font
         self._txt_color = txt_color
         self._bg_color = bg_color
         self._operation = operation
         self._center = (0, 0)
+        self._velocity = velocity
         txt_size = txt_font.size(operation.get_text())
         if txt_size[0] > txt_size[1]:
             max_txt_size = txt_size[0]
@@ -72,7 +76,7 @@ class Ball(object):
         Accessor to the center position.
         => Tuple of 2 integers.
         """
-        return self._center
+        return tuple([int(x) for x in self._center])
 
     def move_to(self, new_center_position):
         """
@@ -81,10 +85,24 @@ class Ball(object):
         """
         self._center = new_center_position
 
-    def move(self, move_value):
-        """
-        Moves the ball by the values inside move_value.
-        move_value : by how much does it move ? => a tuple of 2 integers
-        """
-        self._center = (self._center[0] + move_value[0],
-                        self._center[1] + move_value[1])
+    def move(self):
+        """
+        Moves the ball by its current velocity.
+        Please notice that this velocity will change whenever the ball hits
+        a wall (a screen side).
+        """
+        expected_new_center = (self._center[0] + self._velocity[0],
+                               self._center[1] + self._velocity[1])
+        self._center = expected_new_center
+        radius = self._diameter / 2 
+        # Ball must not go across left or right wall.                
+        if (self._center[0] < radius 
+           or self._center[0] > self._SCREEN_WIDTH - radius):
+            self._velocity = (-self._velocity[0], self._velocity[1])
+            self._center = (self._center[0] + self._velocity[0],
+                            self._center[1] + self._velocity[1])
+        elif (self._center[1] < radius
+             or self._center[1] > self._SCREEN_HEIGTH - radius):
+            self._velocity = (self._velocity[0], -self._velocity[1])
+            self._center = (self._center[0] + self._velocity[0],
+                            self._center[1] + self._velocity[1])
\ No newline at end of file
diff --git a/elements_painter.py b/elements_painter.py
index b1ab8a1..aab9aa1 100644
--- a/elements_painter.py
+++ b/elements_painter.py
@@ -17,12 +17,12 @@ def paint_ball(ball, surface):
     surface : the destination surface => PyGame.Surface
     """
     pygame.draw.circle(surface, ball.get_bg_color(), ball.get_center(),
-                       ball.get_diameter() / 2)
+                       int(ball.get_diameter() / 2))
     ball_center = ball.get_center()
     txt_width, txt_height = ball.get_txt_font().size(ball.get_operation().
                                                      get_text())
-    txt_position = (ball_center[0] - txt_width / 2,
-                    ball_center[1] - txt_height / 2)
+    txt_position = (int(ball_center[0] - txt_width / 2),
+                    int(ball_center[1] - txt_height / 2))
     txt_surface = ball.get_txt_font().render(
         ball.get_operation().get_text(), color=ball.get_txt_color())
     surface.blit(txt_surface, txt_position)
diff --git a/main.py b/main.py
index 57e2526..13b5cf8 100644
--- a/main.py
+++ b/main.py
@@ -7,7 +7,7 @@ Created on Sat Sep 14 10:57:17 2013
 
 import olpcgames
 import pygame
-import sys
+from sys import exit
 from olpcgames.pangofont import PangoFont
 from pygame.locals import QUIT
 from ball import *
@@ -28,33 +28,23 @@ def main():
         screen = pygame.display.set_mode(size)
         pygame.display.set_caption("Hit the balls")
     clock = pygame.time.Clock()
-    info = pygame.display.Info()
-    screen_size = info.current_w, info.current_h
     font = PangoFont(family='Helvetica', size=16, bold=True)
     BLACK = (0, 0, 0)
     BLUE = (0, 0, 255)
-    YELLOW = (255, 255, 0)
-    RED = (255, 0, 0)
-    GREEN = (0, 255, 0)
-    the_balls = [Ball(font, BLACK, BLUE, Operation(1000, 3000, OPER_MUL)),
-                 Ball(font, BLACK, YELLOW, Operation(120, 45, OPER_SUB)),
-                 Ball(font, BLACK, RED, Operation(9, 3, OPER_DIV)),
-                 Ball(font, BLACK, GREEN, Operation(120, 240, OPER_ADD))]
-    the_balls[0].move((140, 170))
-    the_balls[1].move((400, 300))
-    the_balls[2].move((200, 80))
-    the_balls[3].move((330, 70))
-
+    the_ball = Ball(font, BLACK, BLUE, Operation(1000, 3000, OPER_MUL),
+                    (2, 1.2))
+    the_ball.move_to((140, 170))
+    
     while True:
         screen.fill(BACKGROUND)
-        for ball in the_balls:
-            paint_ball(ball, screen)
-        pygame.display.update()
+        paint_ball(the_ball, screen)
         for event in pygame.event.get():
             if event.type == QUIT:
                 pygame.quit()
-                sys.exit()
+                exit()
+        pygame.display.update()
         clock.tick(FPS)
+        the_ball.move()
 
 if __name__ == "__main__":
     main()