Add graphics window

src/screen.ml

@@ -1,14 +1,15 @@
+let width = 160
+let height = 144
+
 type pixel = {
-  r : char;
-  g : char;
-  b : char;
-  a : char;
+  r : int;
+  g : int;
+  b : int;
+  a : int;
 }
 
 type t = {
-  width  : int;
-  height : int;
-  data   : pixel array;
+  data   : pixel array array;
 }
 
 type control = {
@@ -45,11 +46,9 @@ let get_lcd_control mem =
     bg_display;
   }
 
-let init_screen w h =
+let init =
   {
-    width = w;
-    height = h;
-    data = Array.make_matrix h w { r = 255; g = 255; b = 255; a = 255 }
+    data = Array.make_matrix width height { r = 255; g = 255; b = 255; a = 255 }
   }