* Gallery sets its window size to match the item constraints for tests that need a window boundary

 * Timeline lets you specify a
 * Timeline now offers a truly minimal item scaffold with no theming, background color, or padding

Author: matthew-carroll

lib/src/scenes/gallery.dart

@@ -337,6 +337,14 @@ class Gallery {
       final previousPlatform = debugDefaultTargetPlatformOverride;
       debugDefaultTargetPlatformOverride = item.platform ?? previousPlatform;
 
+      if (itemConstraints != null && itemConstraints.hasBoundedWidth && itemConstraints.hasBoundedHeight) {
+        // Some tests may want to control the size of the window. If we're given bounded
+        // constraints, make the window the biggest allowable size.
+        final previousSize = tester.view.physicalSize;
+        tester.view.physicalSize = itemConstraints.biggest;
+        addTearDown(() => tester.view.physicalSize = previousSize);
+      }
+
       if (item.pumper != null) {
         // Defer to the `pumper` to pump the entire widget tree for this gallery item.
         await item.pumper!.call(tester, itemScaffold, item.description);

lib/src/scenes/timeline.dart

@@ -28,20 +28,24 @@ class Timeline {
     this._description, {
     Directory? directory,
     required String fileName,
-    GoldenSceneItemScaffold itemScaffold = minimalItemScaffold,
+    Size? windowSize,
+    GoldenSceneItemScaffold itemScaffold = standardTimelineItemScaffold,
     required SceneLayout layout,
     GoldenSceneBackground? goldenBackground,
   })  : _directory = directory,
         _fileName = fileName,
+        _windowSize = windowSize,
+        _itemScaffold = itemScaffold,
         _layout = layout,
-        _goldenBackground = goldenBackground,
-        _itemScaffold = itemScaffold;
+        _goldenBackground = goldenBackground;
 
   final String _description;
 
   late final Directory? _directory;
   final String _fileName;
 
+  final Size? _windowSize;
+
   final GoldenSceneItemScaffold _itemScaffold;
 
   final GoldenSceneBackground? _goldenBackground;
@@ -59,7 +63,11 @@ class Timeline {
       throw Exception("Timeline was already set up, but tried to call setup() again.");
     }
 
-    _setup = _TimelineSetup(delegate);
+    _setup = _TimelineSetup((tester) async {
+      _configureWindowSize(tester);
+
+      await delegate(tester);
+    });
 
     return this;
   }
@@ -73,6 +81,8 @@ class Timeline {
     }
 
     _setup = _TimelineSetup((tester) async {
+      _configureWindowSize(tester);
+
       final widgetTree = _itemScaffold(tester, sceneBuilder());
       await tester.pumpWidget(widgetTree);
     });
@@ -89,13 +99,23 @@ class Timeline {
     }
 
     _setup = _TimelineSetup((tester) async {
+      _configureWindowSize(tester);
+
       final widgetTree = _itemScaffold(tester, widget);
       await tester.pumpWidget(widgetTree);
     });
 
     return this;
   }
 
+  void _configureWindowSize(WidgetTester tester) {
+    if (_windowSize != null) {
+      final previousWindowSize = tester.view.physicalSize;
+      tester.view.physicalSize = _windowSize;
+      addTearDown(() => tester.view.physicalSize = previousWindowSize);
+    }
+  }
+
   /// Take a golden photo screenshot of the current Flutter UI.
   ///
   /// {@template golden_image_bounds_default_finder}
@@ -566,7 +586,9 @@ class TimelineTestContext {
   final scratchPad = <String, dynamic>{};
 }
 
-Widget minimalItemScaffold(WidgetTester tester, Widget content) {
+/// The standard [GoldenSceneItemScaffold] that wraps the content of a [Timeline], which
+/// includes a dark theme, a dark background color, and some padding around the content.
+Widget standardTimelineItemScaffold(WidgetTester tester, Widget content) {
   return MaterialApp(
     theme: ThemeData(
       brightness: Brightness.dark,
@@ -586,3 +608,18 @@ Widget minimalItemScaffold(WidgetTester tester, Widget content) {
     debugShowCheckedModeBanner: false,
   );
 }
+
+/// An absolute minimal [GoldenSceneItemScaffold] that wraps the content within a [Timeline].
+Widget minimalTimelineItemScaffold(WidgetTester tester, Widget content) {
+  return MaterialApp(
+    theme: ThemeData(
+      fontFamily: goldenBricks,
+    ),
+    home: Center(
+      child: GoldenImageBounds(
+        child: content,
+      ),
+    ),
+    debugShowCheckedModeBanner: false,
+  );
+}