[TabButton] Change padding, how color set is picked and background

Still not really satisfied with the looks, but it's a bit better.

style/qtquickcontrols/TabButton.qml

@@ -3,7 +3,6 @@
  */
 
 import QtQuick 2.15
-import QtQuick.Controls 2.15 as Controls
 import QtQuick.Templates 2.15 as T
 import org.kde.kirigami 2.14 as Kirigami
 import "impl"
@@ -11,8 +10,8 @@ import "impl"
 T.TabButton {
     id: control
 
-    readonly property bool __inHeader: Controls.TabBar.position === Controls.TabBar.Header
-    readonly property bool __inFooter: Controls.TabBar.position === Controls.TabBar.Footer
+    readonly property bool __inHeader: T.TabBar.position === T.TabBar.Header
+    readonly property bool __inFooter: T.TabBar.position === T.TabBar.Footer
 
     implicitWidth: Math.max(implicitBackgroundWidth + leftInset + rightInset,
                             implicitContentWidth + leftPadding + rightPadding,
@@ -22,12 +21,28 @@ T.TabButton {
                              implicitIndicatorHeight + topPadding + bottomPadding)
 
     padding: Kirigami.Units.mediumSpacing
+    leftPadding: {
+        if ((!contentItem.hasIcon && contentItem.textBesideIcon) // False if contentItem has been replaced
+            || display == T.AbstractButton.TextOnly
+            || display == T.AbstractButton.TextUnderIcon) {
+            return Kirigami.Units.mediumHorizontalPadding
+        } else {
+            return control.horizontalPadding
+        }
+    }
+    rightPadding: {
+        if (contentItem.hasLabel && display != T.AbstractButton.IconOnly) { // False if contentItem has been replaced
+            return Kirigami.Units.mediumHorizontalPadding
+        } else {
+            return control.horizontalPadding
+        }
+    }
     spacing: Kirigami.Units.mediumSpacing
 
     icon.width: Kirigami.Units.iconSizes.auto
     icon.height: Kirigami.Units.iconSizes.auto
 
-    Kirigami.Theme.colorSet: Kirigami.Theme.Button
+    Kirigami.Theme.colorSet: control.checked || control.down ? Kirigami.Theme.Button : (T.TabBar.tabBar.Kirigami.Theme.colorSet ?? Kirigami.Theme.Button)
     Kirigami.Theme.inherit: !(background && background.visible)
 
     contentItem: IconLabelContent {
@@ -35,21 +50,25 @@ T.TabButton {
     }
 
     //TODO: tweak the appearance. This is just to have something usable and reasonably close to what we want.
-    background: Rectangle {
-        visible: control.checked
+    background: Kirigami.ShadowedRectangle {
+//         visible: control.checked
+//             && !(control.ListView.view
+//                 && control.ListView.view.highlightItem
+//                 && control.ListView.view.highlightItem.visible)
         implicitHeight: Kirigami.Units.mediumControlHeight
         implicitWidth: implicitHeight
-        color: Kirigami.Theme.alternateBackgroundColor
+        color: control.checked || control.down ? Kirigami.Theme.alternateBackgroundColor : Kirigami.Theme.backgroundColor
+
         Rectangle {
-            id: line
+            id: separatorLine
             anchors {
                 left: parent.left
                 right: parent.right
                 top: control.__inFooter ? parent.top : undefined
                 bottom: control.__inHeader ? parent.bottom : undefined
             }
-            height: Kirigami.Units.highlightLineThickness
-            color: Kirigami.Theme.focusColor
+            height: control.checked ? Kirigami.Units.highlightLineThickness : 1
+            color: control.hovered || control.checked || control.visualFocus ? Kirigami.Theme.focusColor : Kirigami.Theme.separatorColor
         }
     }
 }