[WIP] Fix Android mouse scroll wheel input

shell/platform/android/io/flutter/embedding/android/AndroidTouchProcessor.java

@@ -1,9 +1,11 @@
 package io.flutter.embedding.android;
 
+import android.content.Context;
 import android.graphics.Matrix;
 import android.os.Build;
 import android.view.InputDevice;
 import android.view.MotionEvent;
+import android.view.ViewConfiguration;
 import androidx.annotation.IntDef;
 import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
@@ -138,7 +140,8 @@ public boolean onTouchEvent(@NonNull MotionEvent event, @NonNull Matrix transfor
                 || maskedAction == MotionEvent.ACTION_POINTER_UP);
     if (updateForSinglePointer) {
       // ACTION_DOWN and ACTION_POINTER_DOWN always apply to a single pointer only.
-      addPointerForIndex(event, event.getActionIndex(), pointerChange, 0, transformMatrix, packet);
+      addPointerForIndex(
+          event, event.getActionIndex(), pointerChange, 0, transformMatrix, packet, null);
     } else if (updateForMultiplePointers) {
       // ACTION_UP and ACTION_POINTER_UP may contain position updates for other pointers.
       // We are converting these updates to move events here in order to preserve this data.
@@ -147,18 +150,25 @@ public boolean onTouchEvent(@NonNull MotionEvent event, @NonNull Matrix transfor
       for (int p = 0; p < pointerCount; p++) {
         if (p != event.getActionIndex() && event.getToolType(p) == MotionEvent.TOOL_TYPE_FINGER) {
           addPointerForIndex(
-              event, p, PointerChange.MOVE, POINTER_DATA_FLAG_BATCHED, transformMatrix, packet);
+              event,
+              p,
+              PointerChange.MOVE,
+              POINTER_DATA_FLAG_BATCHED,
+              transformMatrix,
+              packet,
+              null);
         }
       }
       // It's important that we're sending the UP event last. This allows PlatformView
       // to correctly batch everything back into the original Android event if needed.
-      addPointerForIndex(event, event.getActionIndex(), pointerChange, 0, transformMatrix, packet);
+      addPointerForIndex(
+          event, event.getActionIndex(), pointerChange, 0, transformMatrix, packet, null);
     } else {
       // ACTION_MOVE may not actually mean all pointers have moved
       // but it's the responsibility of a later part of the system to
       // ignore 0-deltas if desired.
       for (int p = 0; p < pointerCount; p++) {
-        addPointerForIndex(event, p, pointerChange, 0, transformMatrix, packet);
+        addPointerForIndex(event, p, pointerChange, 0, transformMatrix, packet, null);
       }
     }
 
@@ -183,7 +193,7 @@ public boolean onTouchEvent(@NonNull MotionEvent event, @NonNull Matrix transfor
    * @param event The generic motion event being processed.
    * @return True if the event was handled.
    */
-  public boolean onGenericMotionEvent(@NonNull MotionEvent event) {
+  public boolean onGenericMotionEvent(@NonNull MotionEvent event, Context context) {
     // Method isFromSource is only available in API 18+ (Jelly Bean MR2)
     // Mouse hover support is not implemented for API < 18.
     boolean isPointerEvent =
@@ -203,7 +213,8 @@ public boolean onGenericMotionEvent(@NonNull MotionEvent event) {
     packet.order(ByteOrder.LITTLE_ENDIAN);
 
     // ACTION_HOVER_MOVE always applies to a single pointer only.
-    addPointerForIndex(event, event.getActionIndex(), pointerChange, 0, IDENTITY_TRANSFORM, packet);
+    addPointerForIndex(
+        event, event.getActionIndex(), pointerChange, 0, IDENTITY_TRANSFORM, packet, context);
     if (packet.position() % (POINTER_DATA_FIELD_COUNT * BYTES_PER_FIELD) != 0) {
       throw new AssertionError("Packet position is not on field boundary.");
     }
@@ -219,7 +230,8 @@ private void addPointerForIndex(
       int pointerChange,
       int pointerData,
       Matrix transformMatrix,
-      ByteBuffer packet) {
+      ByteBuffer packet,
+      Context context) {
     if (pointerChange == -1) {
       return;
     }
@@ -335,11 +347,17 @@ private void addPointerForIndex(
     packet.putLong(pointerData); // platformData
 
     if (signalKind == PointerSignalKind.SCROLL) {
-      packet.putDouble(-event.getAxisValue(MotionEvent.AXIS_HSCROLL)); // scroll_delta_x
-      packet.putDouble(-event.getAxisValue(MotionEvent.AXIS_VSCROLL)); // scroll_delta_y
+      double verticalScaleFactor = 1.0;
+      if (context != null) {
+        verticalScaleFactor = ViewConfiguration.get(context).getScaledVerticalScrollFactor();
+      }
+      packet.putDouble(-event.getAxisValue(MotionEvent.AXIS_X, pointerIndex)); // scroll_delta_x
+      packet.putDouble(
+          verticalScaleFactor
+              * -event.getAxisValue(MotionEvent.AXIS_Y, pointerIndex)); // scroll_delta_y
     } else {
       packet.putDouble(0.0); // scroll_delta_x
-      packet.putDouble(0.0); // scroll_delta_x
+      packet.putDouble(0.0); // scroll_delta_y
     }
 
     if (isTrackpadPan) {

shell/platform/android/io/flutter/embedding/android/FlutterView.java

@@ -952,7 +952,8 @@ public boolean onTouchEvent(@NonNull MotionEvent event) {
   @Override
   public boolean onGenericMotionEvent(@NonNull MotionEvent event) {
     boolean handled =
-        isAttachedToFlutterEngine() && androidTouchProcessor.onGenericMotionEvent(event);
+        isAttachedToFlutterEngine()
+            && androidTouchProcessor.onGenericMotionEvent(event, getContext());
     return handled ? true : super.onGenericMotionEvent(event);
   }
 

shell/platform/android/io/flutter/view/FlutterView.java

@@ -482,7 +482,8 @@ public boolean onHoverEvent(MotionEvent event) {
    */
   @Override
   public boolean onGenericMotionEvent(MotionEvent event) {
-    boolean handled = isAttached() && androidTouchProcessor.onGenericMotionEvent(event);
+    boolean handled =
+        isAttached() && androidTouchProcessor.onGenericMotionEvent(event, getContext());
     return handled ? true : super.onGenericMotionEvent(event);
   }
 

sky/packages/sky_engine/lib/_embedder.yaml

@@ -1,33 +1,33 @@
-# This file is suitable for use within the tree. A different _embedder.yaml
-# is generated by the BUILD.gn in this directory. Changes here must be
-# mirrored there.
+# This file is generated by //flutter/sky/packages/sky_engine:_embedder_yaml
+# Do not modify this file directly. Instead, update the build file.
+
 embedded_libs:
-  "dart:async": "../../../../../third_party/dart/sdk/lib/async/async.dart"
-  "dart:collection": "../../../../../third_party/dart/sdk/lib/collection/collection.dart"
-  "dart:convert": "../../../../../third_party/dart/sdk/lib/convert/convert.dart"
-  "dart:core": "../../../../../third_party/dart/sdk/lib/core/core.dart"
-  "dart:developer": "../../../../../third_party/dart/sdk/lib/developer/developer.dart"
-  "dart:ffi": "../../../../../third_party/dart/sdk/lib/ffi/ffi.dart"
-  "dart:html": "../../../../../third_party/dart/sdk/lib/html/html_dart2js.dart"
-  "dart:io": "../../../../../third_party/dart/sdk/lib/io/io.dart"
-  "dart:isolate": "../../../../../third_party/dart/sdk/lib/isolate/isolate.dart"
-  "dart:js": "../../../../../third_party/dart/sdk/lib/js/js.dart"
-  "dart:js_interop": "../../../../../third_party/dart/sdk/lib/js_interop/js_interop.dart"
-  "dart:js_interop_unsafe": "../../../../../third_party/dart/sdk/lib/js_interop_unsafe/js_interop_unsafe.dart"
-  "dart:js_util": "../../../../../third_party/dart/sdk/lib/js_util/js_util.dart"
-  "dart:math": "../../../../../third_party/dart/sdk/lib/math/math.dart"
-  "dart:typed_data": "../../../../../third_party/dart/sdk/lib/typed_data/typed_data.dart"
-  "dart:ui": "../../../../lib/ui/ui.dart"
-  "dart:ui_web": "../../../../lib/web_ui/lib/ui_web/src/ui_web.dart"
+  "dart:async": "async/async.dart"
+  "dart:collection": "collection/collection.dart"
+  "dart:convert": "convert/convert.dart"
+  "dart:core": "core/core.dart"
+  "dart:developer": "developer/developer.dart"
+  "dart:ffi": "ffi/ffi.dart"
+  "dart:html": "html/html_dart2js.dart"
+  "dart:io": "io/io.dart"
+  "dart:isolate": "isolate/isolate.dart"
+  "dart:js": "js/js.dart"
+  "dart:js_interop": "js_interop/js_interop.dart"
+  "dart:js_interop_unsafe": "js_interop_unsafe/js_interop_unsafe.dart"
+  "dart:js_util": "js_util/js_util.dart"
+  "dart:math": "math/math.dart"
+  "dart:typed_data": "typed_data/typed_data.dart"
+  "dart:ui": "ui/ui.dart"
+  "dart:ui_web": "ui_web/ui_web.dart"
 
-  "dart:_http": "../../../../../third_party/dart/sdk/lib/_http/http.dart"
-  "dart:_interceptors": "../../../../../third_party/dart/sdk/lib/_interceptors/interceptors.dart"
+  "dart:_http": "_http/http.dart"
+  "dart:_interceptors": "_interceptors/interceptors.dart"
   # The _internal library is needed as some implementations bleed into the
   # public API, e.g. List being Iterable by virtue of implementing
   # EfficientLengthIterable. Not including this library yields analysis errors.
-  "dart:_internal": "../../../../../third_party/dart/sdk/lib/internal/internal.dart"
+  "dart:_internal": "internal/internal.dart"
   # The _js_annotations library is also needed for the same reasons as _internal.
-  "dart:_js_annotations": "../../../../../third_party/dart/sdk/lib/js/_js_annotations.dart"
+  "dart:_js_annotations": "_js_annotations/_js_annotations.dart"
   # The _js_types library is also needed for the same reasons as _internal.
-  "dart:_js_types": "../../../../../third_party/dart/sdk/lib/_internal/js_shared/lib/js_types.dart"
+  "dart:_js_types": "_js_types/js_types.dart"
   "dart:nativewrappers": "_empty.dart"