QML: Add positiveModulo() JS helper function

2 files changed, 15 insertions, 3 deletions

diff --git a/res/qml/Library.qml b/res/qml/Library.qml
index 7b88561f25..d6589927ef 100644
--- a/res/qml/Library.qml
+++ b/res/qml/Library.qml
@@ -28,9 +28,7 @@ Item {
                 if (rowCount == 0)
                     return ;
 
-                let newIndex = currentIndex = (currentIndex + value) % rowCount;
-                while (newIndex < 0)newIndex += rowCount
-                currentIndex = newIndex;
+                currentIndex = Mixxx.MathUtils.positiveModulo(currentIndex + value, rowCount);
             }
 
             function loadSelectedTrackIntoNextAvailableDeck(play) {
diff --git a/res/qml/Mixxx/MathUtils.mjs b/res/qml/Mixxx/MathUtils.mjs
index e7b500b7b4..5e69447ba9 100644
--- a/res/qml/Mixxx/MathUtils.mjs
+++ b/res/qml/Mixxx/MathUtils.mjs
@@ -7,3 +7,17 @@
 export const clamp = function(value, min, max) {
     return Math.max(Math.min(value, max), min);
 };
+
+/**
+ * @param {number} x Value
+ * @param {number} m Modulus
+ * @returns {number} Result of y where y = x modulo m and y > 0
+ */
+export const positiveModulo = function(x, m) {
+    console.assert(m > 0);
+    let result = x % m;
+    while (result < 0) {
+        result += m;
+    }
+    return result;
+};