From adeb6ca8a9668e12cd04f864dd7914e94bc67883 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Tue, 16 Mar 2021 22:52:43 -0500
Subject: [PATCH] feat: implement window x, window y and ly compare registers

---
 src/bus.rs | 6 ++++++
 src/ppu.rs | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/src/bus.rs b/src/bus.rs
index 3101199..b243803 100644
--- a/src/bus.rs
+++ b/src/bus.rs
@@ -130,9 +130,12 @@ impl Bus {
                     0xFF42 => self.ppu.pos.scroll_y,
                     0xFF43 => self.ppu.pos.scroll_x,
                     0xFF44 => self.ppu.pos.line_y,
+                    0xFF45 => self.ppu.pos.ly_compare as u8,
                     0xFF47 => self.ppu.monochrome.bg_palette.into(),
                     0xFF48 => self.ppu.monochrome.obj_palette_0.into(),
                     0xFF49 => self.ppu.monochrome.obj_palette_1.into(),
+                    0xFF4A => self.ppu.pos.window_y,
+                    0xFF4B => self.ppu.pos.window_x,
                     _ => unimplemented!("Unable to read {:#06X} in I/O Registers", addr),
                 }
             }
@@ -213,9 +216,12 @@ impl Bus {
                     0xFF42 => self.ppu.pos.scroll_y = byte,
                     0xFF43 => self.ppu.pos.scroll_x = byte,
                     0xFF44 => self.ppu.pos.line_y = byte,
+                    0xFF45 => self.ppu.pos.ly_compare = byte == 0x01, // FIXME: We don't consider the possibility of a byte being different form 0x00 or 0x01
                     0xFF47 => self.ppu.monochrome.bg_palette = byte.into(),
                     0xFF48 => self.ppu.monochrome.obj_palette_0 = byte.into(),
                     0xFF49 => self.ppu.monochrome.obj_palette_1 = byte.into(),
+                    0xFF4A => self.ppu.pos.window_y = byte,
+                    0xFF4B => self.ppu.pos.window_x = byte,
                     0xFF50 => {
                         // Disable Boot ROM
                         if byte != 0 {
diff --git a/src/ppu.rs b/src/ppu.rs
index 223c47e..ac34d29 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -167,6 +167,9 @@ pub struct ScreenPosition {
     pub scroll_y: u8,
     pub scroll_x: u8,
     pub line_y: u8,
+    pub ly_compare: bool,
+    pub window_y: u8,
+    pub window_x: u8,
 }
 
 bitfield! {