fix(menus): align menus and actions with KDE HIG

src/qml/SubtitleTracksMenu.qml

@@ -11,6 +11,7 @@ import org.kde.ki18n
 // Checkable list of subtitle tracks, for the primary or the secondary subtitle.
 AppMenu {
     id: root
+    icon.name: isPrimary ? "text-x-generic" : "text-x-script"
 
     required property MpvItem mpv
     property bool isPrimary: true
@@ -36,13 +37,16 @@ AppMenu {
 
     enabled: mpv.subtitleTracks.length > 0
 
+    ButtonGroup { id: tracksGroup; exclusive: true }
+
     AppMenuItem {
         text: KI18n.i18nc("@item:inmenu no subtitle", "None")
         checkable: true
+        ButtonGroup.group: tracksGroup
         checked: root.selectedId === 0
         onTriggered: {
             root.select(0)
-            // Clicking a checked item unchecks it, which drops the binding.
+            // Keep mpv authoritative after MenuItem updates its checked state.
             checked = Qt.binding(() => root.selectedId === 0)
         }
     }
@@ -50,13 +54,18 @@ AppMenu {
     Instantiator {
         model: root.mpv.subtitleTracks
         delegate: AppMenuItem {
+            id: trackItem
             required property var modelData
             text: root.trackLabel(modelData)
             checkable: true
+            ButtonGroup.group: tracksGroup
             checked: modelData.id === root.selectedId
             // mpv cannot show one track in both places.
             enabled: modelData.id !== root.otherId
-            onTriggered: root.select(modelData.id)
+            onTriggered: {
+                root.select(modelData.id)
+                checked = Qt.binding(() => trackItem.modelData.id === root.selectedId)
+            }
         }
         onObjectAdded: (index, object) => root.insertItem(index + 1, object)
         onObjectRemoved: (index, object) => root.removeItem(object)