Restore always-on thumbnail diorama and gate behind a new setting

The gaze-only thumbnail diorama experiment never read right — the
parallax pop only registered while the cell was hovered, which lost
the overall sense of depth in the grid. Restore the always-on layout
from before that series of commits (foreground at z=24, ScaleHoverEffect
on the container) and introduce a Diorama Thumbnails toggle that's
shown only when Reduce Motion is off, so users who want the flat look
without disabling all motion have an opt-out.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: illixion

SpatialStash/SpatialStash/Model/AppModel.swift

@@ -562,6 +562,23 @@ class AppModel {
         reduceMotion || systemReduceMotion
     }
 
+    /// When true, gallery thumbnails render the two-layer diorama with the
+    /// foreground popped forward in z. Independent from Reduce Motion: a
+    /// user may want the parallax-free look without disabling other motion.
+    /// Forced off when `effectiveReduceMotion` is true — read
+    /// `effectiveThumbnailDiorama` at use sites.
+    var thumbnailDiorama: Bool {
+        didSet {
+            if thumbnailDiorama != oldValue {
+                UserDefaults.standard.set(thumbnailDiorama, forKey: "thumbnailDiorama")
+            }
+        }
+    }
+
+    var effectiveThumbnailDiorama: Bool {
+        thumbnailDiorama && !effectiveReduceMotion
+    }
+
     /// When true, image viewer windows have rounded corners.
     var roundedCorners: Bool {
         didSet {
@@ -827,6 +844,11 @@ class AppModel {
         // Accessibility setting overrides via effectiveReduceMotion)
         let loadedReduceMotion = UserDefaults.standard.bool(forKey: "reduceMotion")
 
+        // Load thumbnail diorama preference (default: true)
+        let loadedThumbnailDiorama = UserDefaults.standard.object(forKey: "thumbnailDiorama") != nil
+            ? UserDefaults.standard.bool(forKey: "thumbnailDiorama")
+            : true
+
         // Load rounded corners (default: true)
         let loadedRoundedCorners = UserDefaults.standard.object(forKey: "roundedCorners") != nil
             ? UserDefaults.standard.bool(forKey: "roundedCorners")
@@ -907,6 +929,7 @@ class AppModel {
         self.spatial3DMaxResolution = loadedSpatial3DMaxResolution
         self.dioramaDistance = loadedDioramaDistance
         self.reduceMotion = loadedReduceMotion
+        self.thumbnailDiorama = loadedThumbnailDiorama
         self.roundedCorners = loadedRoundedCorners
         self.openMediaInNewWindows = loadedOpenMediaInNewWindows
         self.rememberImageEnhancements = loadedRememberImageEnhancements

SpatialStash/SpatialStash/Views/DioramaForegroundHoverEffect.swift

@@ -22,19 +22,16 @@ struct GalleryThumbnailView: View {
             // Background
             Color.secondary.opacity(0.2)
 
-            if let dioramaPair, !appModel.effectiveReduceMotion {
-                // Both layers always rendered, both at z=0 — looks flat at
-                // rest. On gaze the foreground scales beyond the container's
-                // hover scale and tilts slightly, reading as forward motion
-                // without needing dynamic z-offset (which the hover-effect
-                // transform vocabulary doesn't expose).
+            if let dioramaPair, appModel.effectiveThumbnailDiorama {
+                // Two-layer diorama: blurred-subject backdrop, masked foreground
+                // popped forward in z for an Apple TV-style parallax pop.
                 Image(uiImage: dioramaPair.backdrop)
                     .resizable()
                     .scaledToFill()
                 Image(uiImage: dioramaPair.foreground)
                     .resizable()
                     .scaledToFill()
-                    .hoverEffect(DioramaForegroundHoverEffect())
+                    .offset(z: 24)
             } else if let loadedImage {
                 Image(uiImage: loadedImage)
                     .resizable()
@@ -81,7 +78,7 @@ struct GalleryThumbnailView: View {
     /// any in-flight or completed result without re-running Vision.
     private func generateDioramaIfPossible() async {
         guard let loadedImage else { return }
-        guard !appModel.effectiveReduceMotion else { return }
+        guard appModel.effectiveThumbnailDiorama else { return }
         let key = image.thumbnailURL
         if let cached = ThumbnailDioramaCache.shared.cached(for: key) {
             dioramaPair = cached

SpatialStash/SpatialStash/Views/Pictures/GalleryThumbnailView.swift

@@ -51,6 +51,10 @@ struct SettingsTabView: View {
                             .foregroundColor(.secondary)
                     }
 
+                    if !appModel.effectiveReduceMotion {
+                        Toggle("Diorama Thumbnails", isOn: $appModel.thumbnailDiorama)
+                    }
+
                     Toggle("Rounded Corners", isOn: $appModel.roundedCorners)
 
                     Toggle("Always Open In New Window", isOn: $appModel.openMediaInNewWindows)