Share pointer movement gate across menus

shell/Ui/PointerMoveGate.qml

@@ -0,0 +1,38 @@
+import QtQuick
+
+// Filters synthetic hover churn from moving delegates under a stationary
+// pointer. Call reset() after keyboard/list mutations, then moved() from a
+// row MouseArea's onPositionChanged before changing cursor selection.
+QtObject {
+  id: root
+
+  property Item referenceItem: null
+  property real threshold: 1
+  property bool primed: false
+  property real lastX: 0
+  property real lastY: 0
+
+  function reset() {
+    root.primed = false
+    root.lastX = 0
+    root.lastY = 0
+  }
+
+  function moved(item, mouse) {
+    if (!item || !mouse) {
+      root.reset()
+      return false
+    }
+
+    var target = root.referenceItem || item
+    var point = item.mapToItem(target, mouse.x, mouse.y)
+    var didMove = root.primed
+      && (Math.abs(point.x - root.lastX) > root.threshold || Math.abs(point.y - root.lastY) > root.threshold)
+
+    root.lastX = point.x
+    root.lastY = point.y
+    root.primed = true
+
+    return didMove
+  }
+}