viewer: option for random transition

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to this project will be documented in this file.
 - support for animated PNG
 - Info: added day filter with item date
 - Widget: option to update image on tap
+- Slideshow / Screen saver: option for random transition
 
 ### Changed
 

lib/model/settings/enums/viewer_transition.dart

@@ -1,5 +1,8 @@
+import 'dart:math';
+
 import 'package:aves/widgets/viewer/controls/controller.dart';
 import 'package:aves_model/aves_model.dart';
+import 'package:collection/collection.dart';
 import 'package:flutter/widgets.dart';
 
 extension ExtraViewerTransition on ViewerTransition {
@@ -15,6 +18,46 @@ extension ExtraViewerTransition on ViewerTransition {
         return PageTransitionEffects.fade(pageController, index, zoomIn: true);
       case ViewerTransition.none:
         return PageTransitionEffects.none(pageController, index);
+      case ViewerTransition.random:
+        return _ViewerTransitionRandomizer.getBuilder(pageController, index);
     }
   }
 }
+
+class _ViewerTransitionRandomizer {
+  static const options = [
+    ViewerTransition.slide,
+    ViewerTransition.parallax,
+    ViewerTransition.fade,
+    ViewerTransition.zoomIn,
+  ];
+
+  static final List<(int, ViewerTransition)> _indexedTransitions = [];
+
+  static TransitionBuilder getBuilder(
+    PageController pageController,
+    int index,
+  ) =>
+      (context, child) {
+        final negative = pageController.hasClients && pageController.position.haveDimensions && (pageController.page! - index).isNegative;
+        final transition = _getTransition(negative ? index - 1 : index);
+        final builder = transition.builder(pageController, index);
+        return builder(context, child);
+      };
+
+  static ViewerTransition _getTransition(int transitionIndex) {
+    var indexedTransition = _indexedTransitions.firstWhereOrNull((v) => v.$1 == transitionIndex);
+    if (indexedTransition != null) {
+      _indexedTransitions.remove(indexedTransition);
+    } else {
+      indexedTransition = (transitionIndex, options[Random().nextInt(options.length)]);
+    }
+    _indexedTransitions.insert(0, indexedTransition);
+    while (_indexedTransitions.length > 3) {
+      _indexedTransitions.removeLast();
+    }
+
+    final (_, transition) = indexedTransition;
+    return transition;
+  }
+}

lib/view/src/settings/enums.dart

@@ -251,6 +251,8 @@ extension ExtraViewerTransitionView on ViewerTransition {
         return context.l10n.viewerTransitionZoomIn;
       case ViewerTransition.none:
         return context.l10n.viewerTransitionNone;
+      case ViewerTransition.random:
+        return context.l10n.widgetDisplayedItemRandom;
     }
   }
 }

plugins/aves_model/lib/src/settings/enums.dart

@@ -40,7 +40,7 @@ enum VideoLoopMode { never, shortOnly, always }
 
 enum VideoResumptionMode { never, ask, always }
 
-enum ViewerTransition { slide, parallax, fade, zoomIn, none }
+enum ViewerTransition { slide, parallax, fade, zoomIn, none, random }
 
 enum WidgetDisplayedItem { random, mostRecent }