use the window color to dim

containments/panel/package/contents/ui/SlidingPanel.qml

@@ -31,7 +31,7 @@ NanoShell.FullScreenPanel {
     property bool userInteracting: false
     property bool expanded: false
 
-    color: "transparent"
+    color: Qt.rgba(0, 0, 0, 0.6 * Math.min(1, offset/contentArea.height))
     property alias contents: contentArea.data
     property int headerHeight
 
@@ -111,11 +111,6 @@ NanoShell.FullScreenPanel {
         to: contentArea.height
     }
 
-    Rectangle {
-        anchors.fill: parent
-        color: Qt.rgba(0, 0, 0, 0.6 * Math.min(1, offset/contentArea.height))
-    }
-
     PlasmaCore.ColorScope {
         anchors.fill: parent
         y: Math.min(0, -height + window.offset)