put shell in subdir, and add nix package

shell/mpris/Controller.qml

@@ -0,0 +1,77 @@
+pragma Singleton
+pragma ComponentBehavior: Bound
+
+import QtQuick
+import Quickshell
+import Quickshell.Io
+import Quickshell.Services.Mpris
+
+Singleton {
+    id: root
+    property MprisPlayer trackedPlayer
+
+    IpcHandler {
+        target: "mpris"
+
+        function next(): void {
+            root.trackedPlayer.next();
+        }
+
+        function prev(): void {
+            root.trackedPlayer.previous();
+        }
+
+        function play(): void {
+            root.trackedPlayer.play();
+        }
+
+        function pause(): void {
+            root.trackedPlayer.pause();
+        }
+
+        function play_pause(): void {
+            if (root.trackedPlayer.isPlaying) {
+                root.trackedPlayer.pause();
+            } else {
+                root.trackedPlayer.play();
+            }
+        }
+    }
+
+    Instantiator {
+        model: Mpris.players
+
+        Connections {
+            required property MprisPlayer modelData
+            target: modelData
+
+            Component.onCompleted: {
+                if (root.trackedPlayer == null || modelData.isPlaying) {
+                    root.trackedPlayer = modelData;
+                }
+            }
+
+            Component.onDestruction: {
+                if (root.trackedPlayer == null || !root.trackedPlayer.isPlaying) {
+                    for (const player of Mpris.players.values) {
+                        if (player.playbackState.isPlaying) {
+                            root.trackedPlayer = player;
+                            break;
+                        }
+                    }
+
+                    if (root.trackedPlayer == null && Mpris.players.values.length != 0) {
+                        root.trackedPlayer = Mpris.players.values[0];
+                    }
+                }
+            }
+
+            function onPlaybackStateChanged() {
+                if (root.trackedPlayer !== modelData)
+                    root.trackedPlayer = modelData;
+            }
+        }
+    }
+
+    function init() {}
+}