Fix color scheme preview

Set inherit to false in the root of the preview item.
Normally you would set ColorSet to View and be done with it, in this
case we need some additional custom stuff because of the custom palette.
BUG:434493

kcms/colors/package/contents/ui/main.qml

@@ -149,9 +149,8 @@ KCM.GridViewKCM {
 
             color: model.palette.window
 
+            Kirigami.Theme.inherit: false
             Kirigami.Theme.highlightColor: model.palette.highlight
-            Kirigami.Theme.highlightedTextColor: model.palette.highlightedText
-            Kirigami.Theme.linkColor: model.palette.link
             Kirigami.Theme.textColor: model.palette.text
 
             Rectangle {
@@ -208,11 +207,26 @@ KCM.GridViewKCM {
                 QtControls.Frame {
                     Layout.fillWidth: true
                     Layout.fillHeight: true
-                    Kirigami.Theme.backgroundColor: model.palette.base
-                    // FIXME Make Frame still visible but without any inner padding
-                    padding: 1
+                    padding: 0
+
                     activeFocusOnTab: false
 
+                    // Frame by default has a transparent background, override it so we can use the view color
+                    // instead.
+                    background: Rectangle {
+                        color: Kirigami.Theme.backgroundColor
+                        border.width: 1
+                        border.color: Qt.rgba(model.palette.text.r, model.palette.text.g, model.palette.text.b, 0.3)
+                    }
+
+                    // We need to set inherit to false here otherwise the child ItemDelegates will not use the
+                    // alternative base color we set here.
+                    Kirigami.Theme.inherit: false
+                    Kirigami.Theme.backgroundColor: model.palette.base
+                    Kirigami.Theme.highlightColor: model.palette.highlight
+                    Kirigami.Theme.highlightedTextColor: model.palette.highlightedText
+                    Kirigami.Theme.linkColor: model.palette.link
+                    Kirigami.Theme.textColor: model.palette.text
                     Column {
                         id: listPreviewColumn
 
@@ -221,7 +235,8 @@ KCM.GridViewKCM {
                             .arg(model.palette.linkVisited)
                             .arg(i18nc("Visited hyperlink", "visited"))
 
-                        width: parent.width
+                        anchors.fill: parent
+                        anchors.margins: 1
 
                         QtControls.ItemDelegate {
                             width: parent.width