Imporove alignment in clipboard and show hint when empty

Adds a hint when the clipboard history is empty to be consistent with all the
other plasmoids, it's not pixel-perfect but good enough. Also improve alignment
of the search and highlight

BUG: 344159

applets/clipboard/contents/ui/ClipboardItemDelegate.qml

@@ -33,11 +33,8 @@ PlasmaComponents.ListItem {
     signal barcode(string uuid)
     signal action(string uuid)
 
-    width: parent.width - units.gridUnit * 2
     height: Math.max(label.height, toolButtonsLayout.implicitHeight) + 2 * units.smallSpacing
 
-    x: -listMargins.left
-
     enabled: true
 
     onClicked: menuItem.itemSelected(UuidRole)
@@ -54,7 +51,7 @@ PlasmaComponents.ListItem {
         height: childrenRect.height
         anchors {
             left: parent.left
-            leftMargin: units.gridUnit / 2
+            leftMargin: units.gridUnit / 2 - listMargins.left
             right: parent.right
             verticalCenter: parent.verticalCenter
         }

applets/clipboard/contents/ui/ClipboardPage.qml

@@ -22,6 +22,7 @@ import QtQuick.Layouts 1.1
 import org.kde.plasma.plasmoid 2.0
 import org.kde.plasma.core 2.0 as PlasmaCore
 import org.kde.plasma.components 2.0 as PlasmaComponents
+import org.kde.plasma.extras 2.0 as PlasmaExtras
 
 ColumnLayout {
     Keys.onPressed: {
@@ -76,12 +77,19 @@ ColumnLayout {
         }
     }
 
+    PlasmaExtras.Heading {
+        id: emptyHint
+        Layout.fillWidth: true
+        level: 3
+        opacity: 0.6
+        visible: clipboardMenu.model.count === 0
+        text: i18n("Clipboard history is empty.")
+    }
+
     RowLayout {
         Layout.fillWidth: true
-        Item {
-            width: units.gridUnit / 2 - parent.spacing
-            height: 1
-        }
+        visible: !emptyHint.visible
+
         PlasmaComponents.TextField {
             id: filter
             placeholderText: i18n("Search")

applets/clipboard/contents/ui/Menu.qml

@@ -37,10 +37,7 @@ PlasmaExtras.ScrollArea {
 
         boundsBehavior: Flickable.StopAtBounds
         interactive: contentHeight > height
-        highlight: PlasmaComponents.Highlight {
-            anchors.bottomMargin: -listMargins.bottom
-            y: 1
-        }
+        highlight: PlasmaComponents.Highlight { }
         highlightMoveDuration: 0
         highlightResizeDuration: 0
         currentIndex: -1