Fix drift in scroll_overlay Android item alignment; small updates

scroll_overlay/README.md

@@ -1,3 +1,7 @@
 # Scroll Overlay
 
-Overlays a native scroll view over the Flutter view. The scroll view displays items of a random color and opacity. The scroll view forwards all touch events it receives to the underlying Flutter view. This way, the scroll behavior of Flutter and native controls can be compared.
+Overlays a native scroll view over the Flutter view.
+The scroll view displays items of a random color and opacity.
+The scroll view forwards all touch events it receives to the
+underlying Flutter view.  This way, the scroll behavior of
+Flutter and native controls can be compared.

scroll_overlay/android/app/src/main/java/io/flutter/scroll_overlay/ScrollOverlayActivity.java

@@ -204,11 +204,23 @@ public OverlayViewHolder(@NonNull View itemView) {
              */
             static final int baseItemExtent = 40;
 
+            // Our desired height is in logical pixels, aka dp, but we have to set the
+            // height in the layout as an integer in physical pixels.  If we just
+            // multiply and round, the rounding errors compared to Flutter will add up,
+            // and can get us noticeably out of alignment within a screenful.  So we
+            // compute the exact total offsets in dp and apply the lossy unit conversion
+            // directly to those.
+            private int offsetToTop(int position) {
+                // This is the sum baseItemExtent + (baseItemExtent + 1) + (baseItemExtent + 2) + ….
+                int topInDp = position * baseItemExtent + position * (position - 1) / 2;
+                return (int) TypedValue
+                        .applyDimension(TypedValue.COMPLEX_UNIT_DIP, topInDp, getResources().getDisplayMetrics());
+            }
+
             void bind(int position) {
                 int color = OVERLAY_COLORS[position % OVERLAY_COLORS.length];
                 itemView.setBackground(new ColorDrawable(color));
-                final int height = (int) TypedValue
-                        .applyDimension(TypedValue.COMPLEX_UNIT_DIP, baseItemExtent + position, getResources().getDisplayMetrics());
+                final int height = offsetToTop(position + 1) - offsetToTop(position);
                 itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, height));
                 TextView textView = itemView.findViewById(R.id.text_view);
                 textView.setText("Android " + position);

scroll_overlay/lib/main.dart

@@ -22,7 +22,7 @@ void main() {
 }
 
 class FlutterDemo extends StatefulWidget {
-  const FlutterDemo({Key? key}) : super(key: key);
+  const FlutterDemo({super.key});
 
   @override
   _FlutterDemoState createState() => _FlutterDemoState();

scroll_overlay/pubspec.lock

@@ -5,53 +5,59 @@ packages:
     dependency: transitive
     description:
       name: characters
-      url: "https://pub.dartlang.org"
+      sha256: e6a326c8af69605aec75ed6c187d06b349707a27fbff8222ca9cc2cff167975c
+      url: "https://pub.dev"
     source: hosted
-    version: "1.2.0"
+    version: "1.2.1"
   collection:
     dependency: transitive
     description:
       name: collection
-      url: "https://pub.dartlang.org"
+      sha256: cfc915e6923fe5ce6e153b0723c753045de46de1b4d63771530504004a45fae0
+      url: "https://pub.dev"
     source: hosted
-    version: "1.15.0"
+    version: "1.17.0"
   flutter:
     dependency: "direct main"
     description: flutter
     source: sdk
     version: "0.0.0"
+  js:
+    dependency: transitive
+    description:
+      name: js
+      sha256: "5528c2f391ededb7775ec1daa69e65a2d61276f7552de2b5f7b8d34ee9fd4ab7"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.6.5"
   material_color_utilities:
     dependency: transitive
     description:
       name: material_color_utilities
-      url: "https://pub.dartlang.org"
+      sha256: d92141dc6fe1dad30722f9aa826c7fbc896d021d792f80678280601aff8cf724
+      url: "https://pub.dev"
     source: hosted
-    version: "0.1.4"
+    version: "0.2.0"
   meta:
     dependency: transitive
     description:
       name: meta
-      url: "https://pub.dartlang.org"
+      sha256: "6c268b42ed578a53088d834796959e4a1814b5e9e164f147f580a386e5decf42"
+      url: "https://pub.dev"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0"
   sky_engine:
     dependency: transitive
     description: flutter
     source: sdk
     version: "0.0.99"
-  typed_data:
-    dependency: transitive
-    description:
-      name: typed_data
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
-      url: "https://pub.dartlang.org"
+      sha256: "80b3257d1492ce4d091729e3a67a60407d227c27241d6927be0130c98e741803"
+      url: "https://pub.dev"
     source: hosted
-    version: "2.1.2"
+    version: "2.1.4"
 sdks:
-  dart: ">=2.14.0 <3.0.0"
+  dart: ">=2.17.0 <3.0.0"

scroll_overlay/pubspec.yaml

@@ -2,7 +2,7 @@ name: scroll_overlay
 description: A Flutter app that overlays a native scroll view over the Flutter view.
 
 environment:
-  sdk: '>=2.12.0 <3.0.0'
+  sdk: '>=2.17.0 <3.0.0'
 
 dependencies:
   flutter: