feat(desktop): preferences file under the state home

The first preference is the controls panel's visible tiles. The file is
written only on a change and keeps keys it does not know, so a broken or
newer file is never clobbered by a shell that only read it. State home
rather than the runtime dir because it must survive a reboot, rather
than ~/.config because the shell writes it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/desktop/Prefs.qml b/desktop/Prefs.qml
new file mode 100644
index 0000000..dd2fdfc
--- /dev/null
+++ b/desktop/Prefs.qml
@@ -0,0 +1,69 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+pragma Singleton
+
+import Quickshell
+import Quickshell.Io
+import QtQuick
+import "island/Controls.js" as Controls
+
+// Preferences that must survive a reboot, in one JSON file under the state
+// home. Only the shell writes it, which is why it is not in ~/.config.
+//
+// Nothing is written until the user changes something. A file that fails to
+// parse reads as the defaults and stays on disk as it is, so a hand edit
+// with a typo is not replaced by a panel that was merely opened.
+Singleton {
+    id: root
+
+    readonly property string path:
+        (Quickshell.env("XDG_STATE_HOME") || Quickshell.env("HOME") + "/.local/state")
+        + "/quickshell/desktop.json"
+
+    // Visible control tiles, in display order.
+    property var controls: Controls.defaults()
+
+    // The whole parsed object, so a write keeps keys this version does not
+    // know about.
+    property var data: ({})
+
+    function setControls(list) {
+        root.controls = Controls.normalize(list);
+        const out = Object.assign({}, root.data, { controls: root.controls });
+        root.data = out;
+        file.setText(JSON.stringify(out, null, 2) + "\n");
+    }
+
+    function reparse() {
+        let parsed = {};
+        try {
+            const v = JSON.parse(file.text());
+            if (v && typeof v === "object" && !Array.isArray(v)) parsed = v;
+        } catch (e) {}
+        root.data = parsed;
+        const next = "controls" in parsed ? Controls.normalize(parsed.controls) : Controls.defaults();
+        // The watch also fires on our own write; compare so it is a no-op.
+        if (JSON.stringify(next) !== JSON.stringify(root.controls)) root.controls = next;
+    }
+
+    FileView {
+        id: file
+        path: root.path
+        atomicWrites: true
+        watchChanges: true
+        printErrors: false
+        onFileChanged: reload()
+        onLoaded: root.reparse()
+        // Missing file: the defaults, and nothing written.
+        onLoadFailed: { root.data = {}; root.controls = Controls.defaults(); }
+    }
+}