fix trembling at parabolic edges

containment/package/contents/ui/background/BackgroundProperties.qml

@@ -25,8 +25,8 @@ Item{
         return (hasLeftBorder && hasRightBorder);
     }
 
-    property int offset: 0
-    property int length: 0
+    property real offset: 0
+    property real length: 0
     property int thickness: 0
     property int screenEdgeMargin: 0
     property real currentOpacity: 0

containment/package/contents/ui/layouts/LayoutsContainer.qml

@@ -298,7 +298,7 @@ Item{
 
         readonly property bool centered: (root.myView.alignment === LatteCore.Types.Center) || (root.myView.alignment === LatteCore.Types.Justify)
         readonly property bool reversed: Qt.application.layoutDirection === Qt.RightToLeft
-        readonly property int parabolicOffsetting: Math.round((startParabolicSpacer.length - endParabolicSpacer.length) / 2)
+        readonly property real parabolicOffsetting: (startParabolicSpacer.length - endParabolicSpacer.length) / 2
         property int inJustifyCenterOffset: 0
 
         alignment: {

containment/package/contents/ui/layouts/ParabolicEdgeSpacer.qml

@@ -24,7 +24,7 @@ Item {
     readonly property int hiddenItemsCount: (parabolic.spread - 1)/2
 
     property int index: -1
-    property int length: 0
+    property real length: 0
 
     Behavior on length {
         id: animatedLengthBehavior