From d3f1957f64b74ba9ba9d8c2d2f1c7faa7bd86938 Mon Sep 17 00:00:00 2001
From: Jonathan Balls <jonathanballs@protonmail.com>
Date: Fri, 4 Oct 2024 11:24:04 +0100
Subject: [PATCH] fix off-by-one error when for scanline number

---
 src/mmu/ppu.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/mmu/ppu.rs b/src/mmu/ppu.rs
index 6ef3749..bae9525 100644
--- a/src/mmu/ppu.rs
+++ b/src/mmu/ppu.rs
@@ -85,13 +85,13 @@ impl PPU {
 
             // Full line takes 114 ticks
             if self.modeclock >= 456 {
+                self.modeclock -= 456;
+                self.ly = (self.ly + 1) % 154;
+
                 if self.ly < SCREEN_HEIGHT as u8 {
                     self.render_scanline(self.ly);
                 }
 
-                self.modeclock -= 456;
-                self.ly = (self.ly + 1) % 154;
-
                 // Enter mode 1 (VBLANK)
                 if self.ly == 144 {
                     self.vblank_irq = true