better alignment

src/shell/qmlpackages/desktop/contents/configuration/panelconfiguration/Ruler.qml

@@ -54,11 +54,13 @@ PlasmaCore.FrameSvgItem {
     }
     SliderHandle {
         id: minimumLengthHandle
+        offset: panel.offset
         graphicElementName: "minslider"
         onValueChanged: panel.minimumLength = value
     }
     SliderHandle {
         id: maximumLengthHandle
+        offset: panel.offset
         graphicElementName: "maxslider"
         onValueChanged: panel.maximumLength = value
     }

src/shell/qmlpackages/desktop/contents/configuration/panelconfiguration/SliderHandle.qml

@@ -33,12 +33,21 @@ PlasmaCore.SvgItem {
 
     property int value
     property string graphicElementName
+    property int offset: 0
 
     onValueChanged: {
         if (panel.location == 5 || panel.location == 6) {
-            y = value
+            y = value + offset - root.height/2
         } else {
-            x = value
+            x = value + offset - root.width/2
+        }
+    }
+
+    onOffsetChanged: {
+        if (panel.location == 5 || panel.location == 6) {
+            y = value + offset - root.height/2
+        } else {
+            x = value + offset - root.width/2
         }
     }
 
@@ -50,9 +59,9 @@ PlasmaCore.SvgItem {
         anchors.fill: parent
         onPositionChanged: {
             if (panel.location == 5 || panel.location == 6) {
-                root.value = parent.y
+                root.value = parent.y - offset + root.height/2
             } else {
-                root.value = parent.x
+                root.value = parent.x - offset + root.width/2
             }
         }
     }