better sytle.

src/Chip8/Opcodes.hs

@@ -14,6 +14,15 @@ import Debug.Trace
 
 import Chip8.State (VMState(..))
 
+xSize :: VMState -> Word8 
+xSize s@VMState { extended = e} =
+  if e then 128 else 64
+
+ySize :: VMState -> Word8 
+ySize s@VMState { extended = e} =
+  if e then 64 else 32
+
+
 runInstruction :: VMState  -- ^ Initial CPU state
                -> Word16   -- ^ Full CPU instruction
                -> VMState  -- ^ Resulting CPU state
@@ -117,7 +126,7 @@ op00EE s@VMState { stack = stack } _ =
 op00FB :: VMState
        -> Word16
        -> VMState
-op00FB s _ = shiftScreen s 4 0
+op00FB s i = shiftScreen s 4 0
 
 -- | Scroll display 4 pixels left
 op00FC :: VMState
@@ -519,7 +528,7 @@ drawSprite s@VMState { display = display, extended = e } x y addr n =
     -- Adds the x,y offset to the relative pixel co-ordinate
     addOffset (sx, sy) = (sx + x, sy + y)
     -- Checks if the pixel co-ordinate is within the display bounds
-    inBounds (x, y) = if e then (x >= 0 && x < 128) && (y >= 0 && y < 64) else (x >= 0 && x < 64) && (y >= 0 && y < 32)
+    inBounds (x, y) = (x >= 0 && x < xSize s) && (y >= 0 && y < ySize s)
     -- Gets the sprite's relative pixels, adds offsets and filters out of bounds
     sprite = filter inBounds $ map addOffset $ getSprite s addr n
     -- Folding func to turn sprite in to updated pixels and flag on collision
@@ -537,14 +546,14 @@ screenCoordinates s@VMState { extended = e } offx offy =
              | x <- [0..127],
                y <- [0..63]]
     where
-      inBounds ((x, y), z) = if e then (x >= 0 && x < 128) && (y >= 0 && y < 64) else (x >= 0 && x < 64) && (y >= 0 && y < 32)
+      inBounds ((x, y), z) = (x >= 0 && x < xSize s) && (y >= 0 && y < ySize s)
 
 shiftScreen :: VMState
             -> Word8            -- ^ x coordinate offset
             -> Word8            -- ^ y coordinate offset
             -> VMState
 shiftScreen s@VMState {display = display } offx offy = 
-    s { display = listArray ((0,0),(127,63)) (repeat False) // display' }
+    s { display = listArray ((0,0),(xSize s - 1, ySize s  - 1)) (repeat False) // display' }
     where
       display' = screenCoordinates s offx offy      
 

src/Chip8/State.hs

@@ -3,7 +3,6 @@ module Chip8.State
       VMState(..)
     , create
     , nextInstruction
-    , showDisplay
     ) where
 
 import Data.Word
@@ -40,7 +39,7 @@ create p g = VMState { memory = listArray (0x0, 0xFFF) memContents
                      , i = 0x0
                      , v = listArray (0x0, 0xF) []
                      , stack = []
-                     , display = listArray ((0,0),(128,64)) (repeat False)
+                     , display = listArray ((0,0),(127,63)) (repeat False)
                      , pressed = S.empty
                      , delayTimer = 0
                      , waitForKeypress = Nothing
@@ -92,12 +91,3 @@ nextInstruction VMState { pc = pc, memory = memory } =
   where
     b1 = fromIntegral $ memory ! pc       -- First byte in instruction
     b2 = fromIntegral $ memory ! (pc + 1) -- Second byte in instruction
-
--- | Returns a string representation of a VM state's display
-showDisplay :: VMState  -- ^ The VM state
-            -> String   -- ^ A string showing the display contents using ascii
-showDisplay s =
-    unlines [unwords [toPixel (display s ! (x, y)) | x <- [0..63]] | y <- [0..31]]
-  where
-    toPixel True = "█"
-    toPixel False = " "

src/Main.hs

@@ -15,11 +15,11 @@ import Graphics.Gloss.Data.Color (black, white)
 import Graphics.Gloss.Data.Display
 import Graphics.Gloss.Interface.Pure.Game
 
-import Chip8.State (VMState(..), create, nextInstruction, showDisplay)
+import Chip8.State (VMState(..), create, nextInstruction)
 import Chip8.Opcodes (runInstruction)
 
 cpuFrequency :: Int
-cpuFrequency = 10
+cpuFrequency = 100
 
 screenFrequency :: Int
 screenFrequency = 1