# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1324232960 -3600
# Node ID 2d6bb0876770d810e7b1898f1d524b4240753ff7
# Parent  6d55dd10da35d44bff06745d6c3c48b0809da8fa
Replaced the use of nested lists with a flat, genuine, global screen array
accessed directly from the update function.
Made use of array transposition when copying the screen array into a surface
array.

diff -r 6d55dd10da35 -r 2d6bb0876770 main.py
--- a/main.py	Sun Dec 18 18:55:01 2011 +0100
+++ b/main.py	Sun Dec 18 19:29:20 2011 +0100
@@ -19,15 +19,16 @@
     """
 
     surface = pygame.Surface((MAX_WIDTH, MAX_HEIGHT), 0, screen)
-    a = pygame.surfarray.pixels3d(surface)
+    sa = pygame.surfarray.pixels3d(surface)
+    a = sa.transpose(1, 0, 2)
 
     # Copy the array to a surface and apply a pixel intensity.
 
     try:
-        a[:] = screen_array
+        a.flat[:] = screen_array
         a *= INTENSITY
     finally:
-        del a
+        del a, sa
 
     # Scale the surface to the dimensions of the host's screen and copy the
     # result to the host's screen.
@@ -46,7 +47,6 @@
     screen = pygame.display.set_mode((WIDTH, HEIGHT), 0)
 
     ula = get_ula()
-    ula_screen = get_screen()
 
     # Test MODE 2.
 
@@ -54,12 +54,12 @@
 
     ula.fill(0x3000, 0x5800 - 320, encode((1, 6), 4))
     ula.fill(0x5800 - 320, 0x8000, encode((2, 7), 4))
-    update(ula_screen, ula)
+    ula_screen = update(ula)
     update_screen(screen, ula_screen)
     mainloop()
 
     ula.screen_start = 0x3000 + 2
-    update(ula_screen, ula)
+    ula_screen = update(ula)
     update_screen(screen, ula_screen)
     mainloop()
 
@@ -69,12 +69,12 @@
 
     ula.fill(0x6000, 0x6f00 + 160, encode((1, 0, 1, 1, 0, 0, 1, 1), 1))
     ula.fill(0x6f00 + 160, 0x7f40, encode((1, 0, 1, 0, 1, 0, 1, 0), 1))
-    update(ula_screen, ula)
+    ula_screen = update(ula)
     update_screen(screen, ula_screen)
     mainloop()
 
     ula.screen_start = 0x6f00 + 160
-    update(ula_screen, ula)
+    ula_screen = update(ula)
     update_screen(screen, ula_screen)
     mainloop()
 
diff -r 6d55dd10da35 -r 2d6bb0876770 ula.py
--- a/ula.py	Sun Dec 18 18:55:01 2011 +0100
+++ b/ula.py	Sun Dec 18 19:29:20 2011 +0100
@@ -4,6 +4,9 @@
 Acorn Electron ULA simulation.
 """
 
+from array import array
+from itertools import repeat
+
 LINES_PER_ROW = 8       # the number of pixel lines per character row
 MAX_HEIGHT = 256        # the height of the screen in pixels
 MAX_SCANLINE = 312      # the number of scanlines in each frame
@@ -13,26 +16,33 @@
 MAX_MEMORY = 0x10000    # the number of addressable memory locations
 BLANK = (0, 0, 0)
 
-def update(screen, ula):
+screen = array("B", repeat(0, MAX_WIDTH * 3 * MAX_HEIGHT))
+
+def update(ula):
 
     """
-    Update the 'screen' array by reading from the 'ula'. This function
-    effectively has the role of the video circuit, but also provides the clock
-    signal to the ULA.
+    Return a screen array by reading from the 'ula'. This function effectively
+    has the role of the video circuit, but also provides the clock signal to the
+    ULA.
     """
 
     ula.vsync()
+    pos = 0
     y = 0
     while y < MAX_SCANLINE:
         x = 0
         while x < MAX_SCANPOS:
             colour = ula.get_pixel_colour()
             if x < MAX_WIDTH and y < MAX_HEIGHT:
-                screen[x][y] = colour
+                screen[pos] = colour[0]; pos += 1
+                screen[pos] = colour[1]; pos += 1
+                screen[pos] = colour[2]; pos += 1
             x += 1
         ula.hsync()
         y += 1
 
+    return screen
+
 class ULA:
 
     "The ULA functionality."
@@ -276,17 +286,6 @@
 
     return [0] * MAX_MEMORY
 
-def get_screen():
-
-    "Return a list of arrays representing the display."
-
-    x = 0
-    screen = []
-    while x < MAX_WIDTH:
-        screen.append([(0, 0, 0)] * MAX_HEIGHT)
-        x += 1
-    return screen
-
 def fill(memory, start, end, value):
     for i in xrange(start, end):
         memory[i] = value
@@ -301,7 +300,6 @@
     # Make a simple two-dimensional array of tuples (three-dimensional in pygame
     # terminology).
 
-    a = get_screen()
-    update(a, ula)
+    a = update(ula)
 
 # vim: tabstop=4 expandtab shiftwidth=4