From 644a1356a85301dd112f866c91a5da41f091ac64 Mon Sep 17 00:00:00 2001
From: Fabien Freling <public@ffreling.com>
Date: Wed, 8 Apr 2015 14:49:24 +0200
Subject: [PATCH] Add LCD control structure.

Also add the Bin module to easily deal with binary.
---
 .merlin       |  2 +-
 src/bit.ml    |  4 ++++
 src/screen.ml | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 src/bit.ml

diff --git a/.merlin b/.merlin
index dfaf66f..e566758 100644
--- a/.merlin
+++ b/.merlin
@@ -1,3 +1,3 @@
 S src
 
-B _build
+B _build/src
diff --git a/src/bit.ml b/src/bit.ml
new file mode 100644
index 0000000..a3bf5ff
--- /dev/null
+++ b/src/bit.ml
@@ -0,0 +1,4 @@
+let is_set num i =
+  if i < 0 then failwith "Invalid bit index."
+  (num lsr i) land 0b00000001 <> 0
+
diff --git a/src/screen.ml b/src/screen.ml
index 5747e37..a1f27ed 100644
--- a/src/screen.ml
+++ b/src/screen.ml
@@ -11,6 +11,40 @@ type t = {
   data   : pixel array;
 }
 
+type control = {
+  lcd_display_enable    : bool;
+  tile_map_select       : int;
+  window_display_enable : bool;
+  tile_data_select      : int;
+  bg_tile_map_select    : int;
+  sprite_size           : int;
+  sprite_enable         : bool;
+  bg_display            : bool;
+}
+
+let get_lcd_control mem =
+  let b = Memory.get mem 0xFF40 |> int_of_char in
+
+  let lcd_display_enable = Bit.is_set b 7 in
+  let tile_map_select = if not (Bit.is_set b 6) then 0x9800 else 0x9c00 in
+  let window_display_enable = Bit.is_set b 5 in
+  let tile_data_select = if not (Bit.is_set b 4) then 0x8800 else 0x8000 in
+  let bg_tile_map_select = if not (Bit.is_set b 3) then 0x9800 else 0x9c00 in
+  let sprite_size = if not (Bit.is_set b 2) then 8 else 16 in
+  let sprite_enable = Bit.is_set b 1 in
+  let bg_display = Bit.is_set b 0 in
+
+  {
+    lcd_display_enable;
+    tile_map_select;
+    window_display_enable;
+    tile_data_select;
+    bg_tile_map_select;
+    sprite_size;
+    sprite_enable;
+    bg_display;
+  }
+
 let init_screen w h =
   {
     width = w;