From 99e5388a46d5d073736f4ba703e5d6205bb94a53 Mon Sep 17 00:00:00 2001
From: CrispyPin <crispin@tasa.se>
Date: Mon, 6 May 2024 11:23:14 +0200
Subject: [PATCH] fix crash when copy rule points to outside the rule bounds
 after a resize

---
 petri/src/lib.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/petri/src/lib.rs b/petri/src/lib.rs
index a46a6a5..2790799 100644
--- a/petri/src/lib.rs
+++ b/petri/src/lib.rs
@@ -418,7 +418,12 @@ impl Dish {
 						}
 					}
 					RuleCellTo::Copy(x, y) => {
-						let cell = old_state[x + y * variant.width];
+						let index = x + y * variant.width;
+						if index >= old_state.len() {
+							// the copy source is outside the rule bounds
+							continue;
+						}
+						let cell = old_state[index];
 						if let Some(cell) = cell {
 							// if the copy source is outside the world, do nothing
 							self.set_cell(px, py, cell);