Reland "ChromeOS/Android trackpad gestures" (flutter#34060)

* Android trackpad gestures

* Try to fix lint problem

Author: moffatman

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

@@ -6,9 +6,12 @@
 import android.view.MotionEvent;
 import androidx.annotation.IntDef;
 import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
 import io.flutter.embedding.engine.renderer.FlutterRenderer;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.util.HashMap;
+import java.util.Map;
 
 /** Sends touch information from Android to Flutter in a format that Flutter understands. */
 public class AndroidTouchProcessor {
@@ -26,7 +29,7 @@ public class AndroidTouchProcessor {
     PointerChange.PAN_ZOOM_UPDATE,
     PointerChange.PAN_ZOOM_END
   })
-  private @interface PointerChange {
+  public @interface PointerChange {
     int CANCEL = 0;
     int ADD = 1;
     int REMOVE = 2;
@@ -48,7 +51,7 @@ public class AndroidTouchProcessor {
     PointerDeviceKind.TRACKPAD,
     PointerDeviceKind.UNKNOWN
   })
-  private @interface PointerDeviceKind {
+  public @interface PointerDeviceKind {
     int TOUCH = 0;
     int MOUSE = 1;
     int STYLUS = 2;
@@ -59,15 +62,15 @@ public class AndroidTouchProcessor {
 
   // Must match the PointerSignalKind enum in pointer.dart.
   @IntDef({PointerSignalKind.NONE, PointerSignalKind.SCROLL, PointerSignalKind.UNKNOWN})
-  private @interface PointerSignalKind {
+  public @interface PointerSignalKind {
     int NONE = 0;
     int SCROLL = 1;
     int UNKNOWN = 2;
   }
 
   // Must match the unpacking code in hooks.dart.
   private static final int POINTER_DATA_FIELD_COUNT = 35;
-  private static final int BYTES_PER_FIELD = 8;
+  @VisibleForTesting static final int BYTES_PER_FIELD = 8;
 
   // This value must match the value in framework's platform_view.dart.
   // This flag indicates whether the original Android pointer events were batched together.
@@ -76,12 +79,12 @@ public class AndroidTouchProcessor {
   @NonNull private final FlutterRenderer renderer;
   @NonNull private final MotionEventTracker motionEventTracker;
 
-  private static final int _POINTER_BUTTON_PRIMARY = 1;
-
   private static final Matrix IDENTITY_TRANSFORM = new Matrix();
 
   private final boolean trackMotionEvents;
 
+  private final Map<Integer, float[]> ongoingPans = new HashMap<>();
+
   /**
    * Constructs an {@code AndroidTouchProcessor} that will send touch event data to the Flutter
    * execution context represented by the given {@link FlutterRenderer}.
@@ -220,6 +223,28 @@ private void addPointerForIndex(
     }
 
     int pointerKind = getPointerDeviceTypeForToolType(event.getToolType(pointerIndex));
+    // We use this in lieu of using event.getRawX and event.getRawY as we wish to support
+    // earlier versions than API level 29.
+    float viewToScreenCoords[] = {event.getX(pointerIndex), event.getY(pointerIndex)};
+    transformMatrix.mapPoints(viewToScreenCoords);
+    long buttons;
+    if (pointerKind == PointerDeviceKind.MOUSE) {
+      buttons = event.getButtonState() & 0x1F;
+      if (buttons == 0
+          && event.getSource() == InputDevice.SOURCE_MOUSE
+          && pointerChange == PointerChange.DOWN) {
+        // Some implementations translate trackpad scrolling into a mouse down-move-up event
+        // sequence with buttons: 0, such as ARC on a Chromebook. See #11420, a legacy
+        // implementation that uses the same condition but converts differently.
+        ongoingPans.put(event.getPointerId(pointerIndex), viewToScreenCoords);
+      }
+    } else if (pointerKind == PointerDeviceKind.STYLUS) {
+      buttons = (event.getButtonState() >> 4) & 0xF;
+    } else {
+      buttons = 0;
+    }
+
+    boolean isTrackpadPan = ongoingPans.containsKey(event.getPointerId(pointerIndex));
 
     int signalKind =
         event.getActionMasked() == MotionEvent.ACTION_SCROLL
@@ -230,39 +255,31 @@ private void addPointerForIndex(
 
     packet.putLong(motionEventId); // motionEventId
     packet.putLong(timeStamp); // time_stamp
-    packet.putLong(pointerChange); // change
-    packet.putLong(pointerKind); // kind
+    if (isTrackpadPan) {
+      packet.putLong(getPointerChangeForPanZoom(pointerChange)); // change
+      packet.putLong(PointerDeviceKind.TRACKPAD); // kind
+    } else {
+      packet.putLong(pointerChange); // change
+      packet.putLong(pointerKind); // kind
+    }
     packet.putLong(signalKind); // signal_kind
     packet.putLong(event.getPointerId(pointerIndex)); // device
     packet.putLong(0); // pointer_identifier, will be generated in pointer_data_packet_converter.cc.
 
-    // We use this in lieu of using event.getRawX and event.getRawY as we wish to support
-    // earlier versions than API level 29.
-    float viewToScreenCoords[] = {event.getX(pointerIndex), event.getY(pointerIndex)};
-    transformMatrix.mapPoints(viewToScreenCoords);
-    packet.putDouble(viewToScreenCoords[0]); // physical_x
-    packet.putDouble(viewToScreenCoords[1]); // physical_y
+    if (isTrackpadPan) {
+      float[] panStart = ongoingPans.get(event.getPointerId(pointerIndex));
+      packet.putDouble(panStart[0]);
+      packet.putDouble(panStart[1]);
+    } else {
+      packet.putDouble(viewToScreenCoords[0]); // physical_x
+      packet.putDouble(viewToScreenCoords[1]); // physical_y
+    }
 
     packet.putDouble(
         0.0); // physical_delta_x, will be generated in pointer_data_packet_converter.cc.
     packet.putDouble(
         0.0); // physical_delta_y, will be generated in pointer_data_packet_converter.cc.
 
-    long buttons;
-    if (pointerKind == PointerDeviceKind.MOUSE) {
-      buttons = event.getButtonState() & 0x1F;
-      // TODO(dkwingsmt): Remove this fix after implementing touchpad gestures
-      // https://github.com/flutter/flutter/issues/23604#issuecomment-524471152
-      if (buttons == 0
-          && event.getSource() == InputDevice.SOURCE_MOUSE
-          && (pointerChange == PointerChange.DOWN || pointerChange == PointerChange.MOVE)) {
-        buttons = _POINTER_BUTTON_PRIMARY;
-      }
-    } else if (pointerKind == PointerDeviceKind.STYLUS) {
-      buttons = (event.getButtonState() >> 4) & 0xF;
-    } else {
-      buttons = 0;
-    }
     packet.putLong(buttons); // buttons
 
     packet.putLong(0); // obscured
@@ -317,12 +334,22 @@ private void addPointerForIndex(
       packet.putDouble(0.0); // scroll_delta_x
     }
 
-    packet.putDouble(0.0); // pan_x
-    packet.putDouble(0.0); // pan_y
+    if (isTrackpadPan) {
+      float[] panStart = ongoingPans.get(event.getPointerId(pointerIndex));
+      packet.putDouble(viewToScreenCoords[0] - panStart[0]);
+      packet.putDouble(viewToScreenCoords[1] - panStart[1]);
+    } else {
+      packet.putDouble(0.0); // pan_x
+      packet.putDouble(0.0); // pan_y
+    }
     packet.putDouble(0.0); // pan_delta_x
     packet.putDouble(0.0); // pan_delta_y
     packet.putDouble(1.0); // scale
     packet.putDouble(0.0); // rotation
+
+    if (isTrackpadPan && getPointerChangeForPanZoom(pointerChange) == PointerChange.PAN_ZOOM_END) {
+      ongoingPans.remove(event.getPointerId(pointerIndex));
+    }
   }
 
   @PointerChange
@@ -354,7 +381,19 @@ private int getPointerChangeForAction(int maskedAction) {
     if (maskedAction == MotionEvent.ACTION_SCROLL) {
       return PointerChange.HOVER;
     }
-    return -1;
+    throw new AssertionError("Unexpected masked action");
+  }
+
+  @PointerChange
+  private int getPointerChangeForPanZoom(int pointerChange) {
+    if (pointerChange == PointerChange.DOWN) {
+      return PointerChange.PAN_ZOOM_START;
+    } else if (pointerChange == PointerChange.MOVE) {
+      return PointerChange.PAN_ZOOM_UPDATE;
+    } else if (pointerChange == PointerChange.UP || pointerChange == PointerChange.CANCEL) {
+      return PointerChange.PAN_ZOOM_END;
+    }
+    throw new AssertionError("Unexpected pointer change");
   }
 
   @PointerDeviceKind