From 87333ac31592c329a000bcba8be8aa568ef12eb3 Mon Sep 17 00:00:00 2001
From: Joel Uckelman <uckelman@nomic.net>
Date: Sun, 10 Sep 2023 00:12:08 +0100
Subject: [PATCH] IncrementPropertly: Corrected bad wrap-around calculation
 when increment is negative.

---
 .../VASSAL/build/module/properties/IncrementProperty.java   | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/vassal-app/src/main/java/VASSAL/build/module/properties/IncrementProperty.java b/vassal-app/src/main/java/VASSAL/build/module/properties/IncrementProperty.java
index aef4213887..d012bcc974 100644
--- a/vassal-app/src/main/java/VASSAL/build/module/properties/IncrementProperty.java
+++ b/vassal-app/src/main/java/VASSAL/build/module/properties/IncrementProperty.java
@@ -82,7 +82,11 @@ public String getNewValue(String oldValue) {
       else if (constraints.isWrap()) {
         final int min = constraints.getMinimumValue();
         final int max = constraints.getMaximumValue();
-        value = min + ((value - min + incr) % (max - min + incr));
+        final int range = max - min + 1;
+        // NB: value - min + incr could be < 0 (but > -range), which is
+        // why we add range and mod a second time to ensure that the
+        // result is in [0,range).
+        value = min + ((value - min + incr) % range + range) % range;
       }
       else {
         value += incr;