quickshell: unify media player selection in a Media singleton

The pill and popout each picked an active MPRIS player independently, so
with multiple players open they disagreed and flipped. Add a Media
singleton that selects one active player with stickiness and bind both
components to it.

dot_config/quickshell/bar/MediaPill.qml

@@ -1,5 +1,4 @@
 import Quickshell
-import Quickshell.Services.Mpris
 import QtQuick
 import QtQuick.Layouts
 import "../shared" as Shared
@@ -7,13 +6,7 @@ import "../shared" as Shared
 BarPill {
     id: root
 
-    readonly property var player: {
-        let players = Mpris.players.values;
-        for (let i = 0; i < players.length; i++) {
-            if (players[i].isPlaying) return players[i];
-        }
-        return players.length > 0 ? players[0] : null;
-    }
+    readonly property var player: Shared.Media.activePlayer
 
     visible: player !== null
     groupName: "media"

dot_config/quickshell/bar/popouts/MediaPopout.qml

@@ -1,5 +1,4 @@
 import Quickshell
-import Quickshell.Services.Mpris
 import QtQuick
 import QtQuick.Layouts
 import "../../shared" as Shared
@@ -13,13 +12,7 @@ Item {
     PopoutBackground { anchors.fill: parent }
     MouseArea { anchors.fill: parent }
 
-    readonly property var player: {
-        let players = Mpris.players.values;
-        for (let i = 0; i < players.length; i++) {
-            if (players[i].isPlaying) return players[i];
-        }
-        return players.length > 0 ? players[0] : null;
-    }
+    readonly property var player: Shared.Media.activePlayer
 
     readonly property bool isPlaying: player?.isPlaying ?? false
     readonly property string trackTitle: player?.trackTitle ?? ""

dot_config/quickshell/shared/Media.qml

@@ -0,0 +1,53 @@
+pragma Singleton
+
+import Quickshell
+import Quickshell.Services.Mpris
+import QtQuick
+
+// Single source of truth for "which MPRIS player is active", so the bar pill and
+// the popout never disagree when several players are open.
+Singleton {
+    id: root
+
+    property var activePlayer: null
+
+    readonly property bool hasPlayer: activePlayer !== null
+    readonly property bool isPlaying: activePlayer?.isPlaying ?? false
+
+    // Choose the active player with stickiness: keep the current one while it
+    // still exists and is playing; otherwise prefer a playing player (scanning
+    // newest-first), else keep a valid current, else fall back to the first.
+    function reevaluate() {
+        let players = Mpris.players.values;
+        if (players.length === 0) { root.activePlayer = null; return; }
+
+        let cur = root.activePlayer;
+        let curValid = cur && players.indexOf(cur) >= 0;
+        if (curValid && cur.isPlaying) return;
+
+        for (let i = players.length - 1; i >= 0; i--) {
+            if (players[i].isPlaying) { root.activePlayer = players[i]; return; }
+        }
+
+        if (curValid) return;
+        root.activePlayer = players[0];
+    }
+
+    // Re-evaluate when the set of players changes…
+    Connections {
+        target: Mpris.players
+        function onValuesChanged() { root.reevaluate(); }
+    }
+
+    // …and when any individual player's playback state changes.
+    Instantiator {
+        model: Mpris.players
+        delegate: Connections {
+            required property var modelData
+            target: modelData
+            function onPlaybackStateChanged() { root.reevaluate(); }
+        }
+    }
+
+    Component.onCompleted: reevaluate()
+}