From f8eb2199c261a0267255e836e99ef327e38bacdf Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 6 Mar 2023 22:49:21 -0500
Subject: [PATCH] Fix relative offset.

---
 Components/9918/Implementation/9918.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Components/9918/Implementation/9918.cpp b/Components/9918/Implementation/9918.cpp
index 1af20b369..03ec60f1d 100644
--- a/Components/9918/Implementation/9918.cpp
+++ b/Components/9918/Implementation/9918.cpp
@@ -269,7 +269,7 @@ void TMS9918<personality>::run_for(const HalfCycles cycles) {
 				if constexpr (is_yamaha_vdp(personality)) {
 					if(
 						this->vertical_active_ &&
-						this->fetch_pointer_.row == ((this->line_interrupt_target_ + Storage<personality>::vertical_offset_) & 0xff)
+						this->fetch_pointer_.row == ((this->line_interrupt_target_ - Storage<personality>::vertical_offset_) & 0xff)
 					) {
 						this->line_interrupt_pending_ = true;
 					}
@@ -1241,7 +1241,7 @@ HalfCycles TMS9918<personality>::get_next_sequence_point() const {
 	}
 
 	if constexpr (is_yamaha_vdp(personality)) {
-		next_line_interrupt_row = (this->line_interrupt_target_ + Storage<personality>::vertical_offset_) & 0xff;
+		next_line_interrupt_row = (this->line_interrupt_target_ - Storage<personality>::vertical_offset_) & 0xff;
 	}
 
 	// If there's actually no interrupt upcoming, despite being enabled, either return