force solidness in behaveAsPlasmaPanel

--when we are able to force solidness even though
the plasma theme may never provides that, because
the svg file has some tranparencies in it. Then
for such cases we support it. Such is case is when
the panel is behaveAsPlasmaPanel and maxLength=100%

containment/package/contents/ui/PanelBox.qml

@@ -256,6 +256,24 @@ Item{
             value: root.isVertical ? shadowsSvgItem.marginsHeight : shadowsSvgItem.marginsWidth
         }
 
+        //! This is used to provide real solidness without any transparency from the plasma theme
+        Rectangle{
+            id: solidBackgroundRectangle
+            anchors.fill: solidBackground
+            color: theme.backgroundColor
+            opacity: behaveAsPlasmaPanel && solidBackground.forceSolidness && plasmoid.configuration.maxLength === 100 ? 1 : 0
+
+            Behavior on opacity{
+                enabled: Latte.WindowSystem.compositingActive
+                NumberAnimation { duration: 2 * barLine.animationTime }
+            }
+
+            Behavior on opacity{
+                enabled: !Latte.WindowSystem.compositingActive
+                NumberAnimation { duration: 0 }
+            }
+        }
+
         PlasmaCore.FrameSvgItem{
             id: solidBackground
             anchors.leftMargin: Latte.WindowSystem.compositingActive ? shadowsSvgItem.margins.left - leftIncreaser : 0
@@ -264,10 +282,11 @@ Item{
             anchors.bottomMargin: Latte.WindowSystem.compositingActive ? shadowsSvgItem.margins.bottom - bottomIncreaser : 0
             anchors.fill:parent
 
-            opacity: (root.solidPanel && !plasmoid.configuration.solidBackgroundForMaximized) || root.forceSolidPanel
-                     || (root.hasExpandedApplet && root.zoomFactor===1 && plasmoid.configuration.panelSize===100)
-                     || !Latte.WindowSystem.compositingActive ?
-                         1 : plasmoid.configuration.panelTransparency / 100
+            opacity: forceSolidness ? 1 : plasmoid.configuration.panelTransparency / 100
+
+            readonly property bool forceSolidness: (root.solidPanel && !plasmoid.configuration.solidBackgroundForMaximized) || root.forceSolidPanel
+                                                   || (root.hasExpandedApplet && root.zoomFactor===1 && plasmoid.configuration.panelSize===100)
+                                                   || !Latte.WindowSystem.compositingActive
 
             property rect efGeometry: Qt.rect(-1,-1,0,0)