From 8149352e6346b98ad639e453a4f32826220c4499 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Sat, 12 Jun 2021 13:41:51 -0500
Subject: [PATCH] fix(ppu): Discard SCX mod 8 pixels from fifo

As of right now, the implementation of this is rudimentary. There are
currently some visual bugs that still need to get worked out
---
 src/ppu.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/ppu.rs b/src/ppu.rs
index 6490f2e..0705daa 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -381,6 +381,15 @@ impl Ppu {
         if self.fifo.is_enabled() {
             use RenderPriority::*;
 
+            if self.x_pos == 0 {
+                // Start of a Scanline
+                let discarded_count = self.pos.scroll_x % 8;
+
+                for _ in 0..discarded_count {
+                    let _ = self.fifo.back.pop_back();
+                }
+            }
+
             // Handle Background Pixel and Sprite FIFO
             let bg_enabled = self.ctrl.bg_win_enabled();
             let obj_enabled = self.ctrl.obj_enabled();