wallpaper: a screen can draw from a gallery folder instead of its hearts

Every wallpaper in the gallery is wide, so hearting a whole folder one
thumbnail at a time is the long way to say "this folder". Each screen
now has a source on the engine page: its hearted list, or one gallery
folder picked by chip, stored as the Wallpapers.groups key in Prefs
(folderH, folderV, "" for the hearts).

A folder that has left the gallery gives an empty pool, so that screen
is left alone rather than quietly falling back to its hearts. The
hearted list stays saved behind a folder source and comes back with the
Hearted chip. Switching source needs nothing from the shuffle: draw()
already drops bag entries that are no longer in the pool.

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

1 files changed, 5 insertions, 3 deletions

diff --git a/desktop/Prefs.qml b/desktop/Prefs.qml
index 9a9b0b7..8634f87 100644
--- a/desktop/Prefs.qml
+++ b/desktop/Prefs.qml
@@ -51,10 +51,11 @@ Singleton {
     property int settingsSidebar: 200
 
     // The wallpaper engine (modules/appearance/WallEngine.qml): on or off,
-    // the interval, a list of paths per screen, and each screen's home, the
-    // wallpaper switching off returns to. In here rather than in list files:
+    // the interval, a list of paths per screen, the gallery folder a screen
+    // draws from instead of its list ("" for the list), and each screen's
+    // home, the wallpaper switching off returns to. In here rather than in list files:
     // the lists can be empty, and an empty FileView write writes nothing.
-    readonly property var wallEngineDefaults: ({ on: false, minutes: 30, h: [], v: [], homeH: "", homeV: "" })
+    readonly property var wallEngineDefaults: ({ on: false, minutes: 30, h: [], v: [], folderH: "", folderV: "", homeH: "", homeV: "" })
     property var wallEngine: wallEngineDefaults
     function setWallEngine(changes) {
         const w = Object.assign({}, root.wallEngine, changes);
@@ -122,6 +123,7 @@ Singleton {
             on: we.on === true,
             minutes: Number.isInteger(we.minutes) && we.minutes >= 1 ? we.minutes : 30,
             h: paths(we.h), v: paths(we.v),
+            folderH: str(we.folderH), folderV: str(we.folderV),
             homeH: str(we.homeH), homeV: str(we.homeV),
         };
     }