i82973 scroll mouse wheel support

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;
@@ -183,7 +185,7 @@ 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 =
@@ -192,7 +194,9 @@ public boolean onGenericMotionEvent(@NonNull MotionEvent event) {
     boolean isMovementEvent =
         (event.getActionMasked() == MotionEvent.ACTION_HOVER_MOVE
             || event.getActionMasked() == MotionEvent.ACTION_SCROLL);
-    if (!isPointerEvent || !isMovementEvent) {
+    if (isPointerEvent && isMovementEvent) {
+      continue;
+    } else {
       return false;
     }
 
@@ -203,14 +207,28 @@ 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.");
     }
     renderer.dispatchPointerDataPacket(packet, packet.position());
     return true;
   }
 
+  /// Passes null for context when it is not available. Note that without context scroll wheel will
+  // not work.
+  private void addPointerForIndex(
+      MotionEvent event,
+      int pointerIndex,
+      int pointerChange,
+      int pointerData,
+      Matrix transformMatrix,
+      ByteBuffer packet) {
+    addPointerForIndex(
+        event, pointerIndex, pointerChange, pointerData, transformMatrix, packet, null);
+  }
+
   // TODO(mattcarroll): consider creating a PointerPacket class instead of using a procedure that
   // mutates inputs.
   private void addPointerForIndex(
@@ -219,7 +237,8 @@ private void addPointerForIndex(
       int pointerChange,
       int pointerData,
       Matrix transformMatrix,
-      ByteBuffer packet) {
+      ByteBuffer packet,
+      Context context) {
     if (pointerChange == -1) {
       return;
     }
@@ -341,12 +360,27 @@ private void addPointerForIndex(
 
     packet.putLong(pointerData); // platformData
 
+    // See android scrollview for insperation.
+    // https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/core/java/android/widget/ScrollView.java?q=function:onGenericMotionEvent%20filepath:widget%2FScrollView.java&ss=android%2Fplatform%2Fsuperproject%2Fmain
     if (signalKind == PointerSignalKind.SCROLL) {
-      packet.putDouble(-event.getAxisValue(MotionEvent.AXIS_HSCROLL)); // scroll_delta_x
-      packet.putDouble(-event.getAxisValue(MotionEvent.AXIS_VSCROLL)); // scroll_delta_y
+      // Default if context is null, chosen to ensure reasonable speed scrolling.
+      double verticalScaleFactor = 48.0;
+      double horizontalScaleFactor = 48.0;
+      if (context != null) {
+        horizontalScaleFactor = ViewConfiguration.get(context).getScaledHorizontalScrollFactor();
+        verticalScaleFactor = ViewConfiguration.get(context).getScaledVerticalScrollFactor();
+      }
+      // We flip the sign of the scroll value below because it aligns the pixel value with the
+      // scroll direction in native android.
+      final double horizontalScrollPixels =
+          horizontalScaleFactor * -event.getAxisValue(MotionEvent.AXIS_HSCROLL, pointerIndex);
+      final double verticalScrollPixels =
+          verticalScaleFactor * -event.getAxisValue(MotionEvent.AXIS_VSCROLL, pointerIndex);
+      packet.putDouble(horizontalScrollPixels); // scroll_delta_x
+      packet.putDouble(verticalScrollPixels); // 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);
   }
 

shell/platform/android/test/io/flutter/embedding/android/AndroidTouchProcessorTest.java

@@ -8,8 +8,11 @@
 import static org.mockito.Mockito.when;
 
 import android.annotation.TargetApi;
+import android.content.Context;
 import android.view.InputDevice;
 import android.view.MotionEvent;
+import android.view.ViewConfiguration;
+import androidx.test.core.app.ApplicationProvider;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import io.flutter.embedding.engine.renderer.FlutterRenderer;
 import java.nio.ByteBuffer;
@@ -58,6 +61,14 @@ private double readPointerPhysicalY(ByteBuffer buffer) {
     return buffer.getDouble(8 * AndroidTouchProcessor.BYTES_PER_FIELD);
   }
 
+  private double readScrollDeltaX(ByteBuffer buffer) {
+    return buffer.getDouble(27 * AndroidTouchProcessor.BYTES_PER_FIELD);
+  }
+
+  private double readScrollDeltaY(ByteBuffer buffer) {
+    return buffer.getDouble(28 * AndroidTouchProcessor.BYTES_PER_FIELD);
+  }
+
   private double readPointerPanX(ByteBuffer buffer) {
     return buffer.getDouble(29 * AndroidTouchProcessor.BYTES_PER_FIELD);
   }
@@ -66,6 +77,11 @@ private double readPointerPanY(ByteBuffer buffer) {
     return buffer.getDouble(30 * AndroidTouchProcessor.BYTES_PER_FIELD);
   }
 
+  /// Utility method when trying to write a new test. Prefer named readPointerXXX.
+  private double readOffset(int offset, ByteBuffer buffer) {
+    return buffer.getDouble(offset * AndroidTouchProcessor.BYTES_PER_FIELD);
+  }
+
   private class MotionEventMocker {
     int pointerId;
     int source;
@@ -81,6 +97,15 @@ MotionEvent mockEvent(int action, float x, float y, int buttonState) {
       MotionEvent event = mock(MotionEvent.class);
       when(event.getDevice()).thenReturn(null);
       when(event.getSource()).thenReturn(source);
+      // Ensure that isFromSource does not auto default to false when source is passed in.
+      when(event.isFromSource(InputDevice.SOURCE_CLASS_POINTER))
+          .thenReturn(source == InputDevice.SOURCE_CLASS_POINTER);
+      when(event.isFromSource(InputDevice.SOURCE_MOUSE))
+          .thenReturn(source == InputDevice.SOURCE_MOUSE);
+      when(event.isFromSource(InputDevice.SOURCE_STYLUS))
+          .thenReturn(source == InputDevice.SOURCE_STYLUS);
+      when(event.isFromSource(InputDevice.SOURCE_TOUCHSCREEN))
+          .thenReturn(source == InputDevice.SOURCE_TOUCHSCREEN);
       when(event.getPointerCount()).thenReturn(1);
       when(event.getActionMasked()).thenReturn(action);
       when(event.getActionIndex()).thenReturn(0);
@@ -89,7 +114,8 @@ MotionEvent mockEvent(int action, float x, float y, int buttonState) {
       when(event.getX(0)).thenReturn(x);
       when(event.getY(0)).thenReturn(y);
       when(event.getToolType(0)).thenReturn(toolType);
-      when(event.isFromSource(InputDevice.SOURCE_CLASS_POINTER)).thenReturn(true);
+      when(event.getAxisValue(MotionEvent.AXIS_HSCROLL, pointerId)).thenReturn(x);
+      when(event.getAxisValue(MotionEvent.AXIS_VSCROLL, pointerId)).thenReturn(y);
       return event;
     }
   }
@@ -220,10 +246,45 @@ public void unexpectedMaskedAction() {
     verify(mockRenderer, never()).dispatchPointerDataPacket(ByteBuffer.allocate(0), 0);
   }
 
+  @Test
+  public void scrollWheel() {
+    // Pointer id must be zero to match actionIndex in mocked event.
+    final int pointerId = 0;
+    MotionEventMocker mocker =
+        new MotionEventMocker(
+            pointerId, InputDevice.SOURCE_CLASS_POINTER, MotionEvent.TOOL_TYPE_MOUSE);
+    final float horizontalScrollValue = -1f;
+    final float verticalScrollValue = .5f;
+    final Context context = ApplicationProvider.getApplicationContext();
+    final double horizontalScaleFactor =
+        ViewConfiguration.get(context).getScaledHorizontalScrollFactor();
+    final double verticalScaleFactor =
+        ViewConfiguration.get(context).getScaledVerticalScrollFactor();
+    // Zero verticalScaleFactor will cause this test to miss bugs.
+    assertEquals("zero horizontal scale factor", true, horizontalScaleFactor != 0);
+    assertEquals("zero vertical scale factor", true, verticalScaleFactor != 0);
+
+    final MotionEvent event =
+        mocker.mockEvent(MotionEvent.ACTION_SCROLL, horizontalScrollValue, verticalScrollValue, 1);
+    boolean handled = touchProcessor.onGenericMotionEvent(event, context);
+
+    InOrder inOrder = inOrder(mockRenderer);
+    inOrder
+        .verify(mockRenderer)
+        .dispatchPointerDataPacket(packetCaptor.capture(), packetSizeCaptor.capture());
+    ByteBuffer packet = packetCaptor.getValue();
+
+    assertEquals(-horizontalScrollValue * horizontalScaleFactor, readScrollDeltaX(packet));
+    assertEquals(-verticalScrollValue * verticalScaleFactor, readScrollDeltaY(packet));
+    verify(event).getAxisValue(MotionEvent.AXIS_HSCROLL, pointerId);
+    verify(event).getAxisValue(MotionEvent.AXIS_VSCROLL, pointerId);
+
+    inOrder.verifyNoMoreInteractions();
+  }
+
   @Test
   public void unexpectedPointerChange() {
     // Regression test for https://github.com/flutter/flutter/issues/129765
-
     MotionEventMocker mocker =
         new MotionEventMocker(0, InputDevice.SOURCE_MOUSE, MotionEvent.TOOL_TYPE_MOUSE);