take into account roundness for pseudo-blur

--in editing mode the panel background blur takes
into account inside the qml window, it is used
as a demonstration for the user. This patch
takes into account the blurred area roundness
in order to not blur faulty areas that are not
going to be blurred in the end.

containment/package/contents/ui/PanelBox.qml

@@ -297,7 +297,7 @@ Item{
         Loader {
             anchors.fill: solidBackground
             active: editModeVisual.inEditMode && root.userShowPanelBackground && plasmoid.configuration.blurEnabled
-            sourceComponent: Item{
+            sourceComponent: Item {
                 Image{
                     id: backTiler
                     anchors.fill: parent
@@ -312,7 +312,7 @@ Item{
 
                 ShaderEffectSource {
                     id: effectSource
-                    anchors.fill: backTiler
+                    anchors.fill: parent
                     visible: false
 
                     sourceItem: backTiler
@@ -321,11 +321,26 @@ Item{
 
                 FastBlur{
                     id: blur
-                    anchors.fill: effectSource
+                    anchors.fill: parent
                     opacity: editModeVisual.appliedOpacity * 1.4
 
                     source: effectSource
                     radius: 50
+                    visible: false
+                }
+
+                OpacityMask {
+                    anchors.horizontalCenter: parent.horizontalCenter
+                    anchors.verticalCenter: parent.verticalCenter
+                    anchors.horizontalCenterOffset: overlayedBackground.painterRectangle.anchors.horizontalCenterOffset
+                    anchors.verticalCenterOffset: overlayedBackground.painterRectangle.anchors.verticalCenterOffset
+
+                    width: overlayedBackground.painterRectangle.width
+                    height: overlayedBackground.painterRectangle.height
+
+                    source: blur
+                    maskSource: overlayedBackground.painterRectangle
+                    opacity: blur.opacity
                 }
             }
         }

containment/package/contents/ui/colorizer/CustomBackground.qml

@@ -66,9 +66,10 @@ Item{
     readonly property bool bothVerticals: (leftBorder && rightBorder)
     readonly property bool bothHorizontals: (bottomBorder && topBorder)
 
-
     readonly property bool drawWithoutRoundness: noOfBorders === 1
 
+    readonly property Item painterRectangle: painter
+
     Binding{
         target: main
         property: "topBorder"