[Chromoting] Add InputMonitor and InputState

remoting/android/java/src/org/chromium/chromoting/InputMonitor.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chromoting;
+
+import android.content.Context;
+import android.graphics.Rect;
+import android.view.GestureDetector;
+import android.view.MotionEvent;
+import android.view.ScaleGestureDetector;
+import android.view.ViewConfiguration;
+
+import org.chromium.base.VisibleForTesting;
+import org.chromium.chromoting.InputState.DetectedAction;
+import org.chromium.chromoting.InputState.StartAction;
+
+/**
+ * A combination of existing Android and chromium motion and touch detectors, and provide a set of
+ * {@link Event} when each kind of touch behavior has been detected.
+ */
+public final class InputMonitor
+        implements GestureDetector.OnGestureListener,
+                   ScaleGestureDetector.OnScaleGestureListener,
+                   TapGestureDetector.OnTapListener {
+    /** Tap with one or more fingers. */
+    private final Event.Raisable<TapEventParameter> mOnTap;
+
+    /** Long press and hold with one or more fingers. */
+    private final Event.Raisable<TapEventParameter> mOnPressAndHold;
+
+    /** Any motion event received. */
+    private final Event.Raisable<MotionEvent> mOnTouchEvent;
+
+    /** Scroll with two fingers. */
+    private final Event.Raisable<TwoPointsEventParameter> mOnScroll;
+
+    /** Fling with two fingers. */
+    private final Event.Raisable<TwoPointsEventParameter> mOnScrollFling;
+
+    /** Fling with one finger. */
+    private final Event.Raisable<TwoPointsEventParameter> mOnFling;
+
+    /** Scale with two fingers. */
+    private final Event.Raisable<ScaleEventParameter> mOnScale;
+
+    /** Swipe with three or more fingers. */
+    private final Event.Raisable<TwoPointsEventParameter> mOnSwipe;
+
+    /** Move with one finger. */
+    private final Event.Raisable<TwoPointsEventParameter> mOnMove;
+
+    private final InputState.Settable mInputState;
+    private final int mEdgeSlopInPx;
+    private final float mSwipeThreshold;
+    private final GestureDetector mScroller;
+    private final ScaleGestureDetector mZoomer;
+    private final TapGestureDetector mTapDetector;
+    private final SwipePinchDetector mSwipePinchDetector;
+
+    // Controls whether InputMonitor treats a scrolling with four or more fingers as a swipe.
+    // TouchInputHandler treats a gesture with three fingers as a swipe. To make sure we can easily

[Lambros, 2016/07/14 18:58:07]

I don't see the need for this flag and I don't think we will ever be concerned
about 4-finger swipes. If, say, a 3-finger swipe shows the keyboard, and a user
swipes 4 fingers and the keyboard still appears (or it fails to appear), will
anybody complain?

I would favor removing this flag and reporting all swipe events (4 finger or
otherwise) to the downstream gesture handlers. Let downstream policy decide what
to do with >= 4-finger gestures. Keep this file as a low-level gesture reporter,
without making policy decisions here.

[Hzj_jie, 2016/07/14 23:18:06]

Personally I think swiping with three or four fingers should be treated
similarly. But current implementation does not handle swiping with four fingers.
But I would prefer to have automatically testing, i.e. generate random gesture
events, send to a view, and compare the output of this InputMonitor and current
implementation. Which means, I need to make sure this class behalves exactly the
same as current implementation.

But if you do not have strong opinion about swiping three or four fingers, I
will change current implementation to avoid this flag.

+    // test the differences between TouchInputHandler and InputMonitor, we can set this variable to

[Lambros, 2016/07/14 18:58:07]

Also, better to avoid flags that make code behave differently under test than
production.

[Hzj_jie, 2016/07/14 23:18:06]

Done.

+    // false to force InputMonitor to behave consistently as TouchInputHandler.
+    private final boolean mSwipeWithMoreFingers;
+
+    private Rect mPanGestureBounds;
+
+    @VisibleForTesting
+    InputMonitor(DesktopViewInterface view, Context context, boolean swipeWithMoreFingers) {
+        mOnTap = new Event.Raisable<>();
+        mOnPressAndHold = new Event.Raisable<>();
+        mOnTouchEvent = new Event.Raisable<>();
+        mOnScroll = new Event.Raisable<>();
+        mOnScrollFling = new Event.Raisable<>();
+        mOnFling = new Event.Raisable<>();
+        mOnScale = new Event.Raisable<>();
+        mOnSwipe = new Event.Raisable<>();
+        mOnMove = new Event.Raisable<>();
+        mInputState = new InputState.Settable();
+        mEdgeSlopInPx = ViewConfiguration.get(context).getScaledEdgeSlop();
+        mSwipeThreshold = 40 * context.getResources().getDisplayMetrics().density;
+        mScroller = new GestureDetector(context, this, null, false);
+        mScroller.setIsLongpressEnabled(false);
+        mZoomer = new ScaleGestureDetector(context, this);
+        mTapDetector = new TapGestureDetector(context, this);
+        mSwipePinchDetector = new SwipePinchDetector(context);
+        view.onClientSizeChanged().add(
+                new Event.ParameterRunnable<SizeChangedEventParameter>() {
+                    @Override
+                    public void run(SizeChangedEventParameter param) {
+                        handleClientSizeChanged(param);
+                    }
+                });
+        // Currently we support only touch events.
+        view.onTouch().add(
+                new Event.ParameterRunnable<TouchEventParameter>() {
+                    @Override
+                    public void run(TouchEventParameter param) {
+                        handleTouch(param);
+                    }
+                });
+        mSwipeWithMoreFingers = swipeWithMoreFingers;
+    }
+
+    public InputMonitor(DesktopViewInterface view, Context context) {
+        this(view, context, true);
+    }
+
+    // -------------- Getters -------------------------------------------------------------
+    public Event<TapEventParameter> onTap() {
+        return mOnTap;
+    }
+
+    public Event<TapEventParameter> onPressAndHold() {
+        return mOnPressAndHold;
+    }
+
+    public Event<MotionEvent> onTouchEvent() {
+        return mOnTouchEvent;
+    }
+
+    public Event<TwoPointsEventParameter> onScroll() {
+        return mOnScroll;
+    }
+
+    public Event<TwoPointsEventParameter> onScrollFling() {
+        return mOnScrollFling;
+    }
+
+    public Event<TwoPointsEventParameter> onFling() {
+        return mOnFling;
+    }
+
+    public Event<ScaleEventParameter> onScale() {
+        return mOnScale;
+    }
+
+    public Event<TwoPointsEventParameter> onSwipe() {
+        return mOnSwipe;
+    }
+
+    public Event<TwoPointsEventParameter> onMove() {
+        return mOnMove;
+    }
+
+    public InputState inputState() {
+        return mInputState;
+    }
+
+    // -------------- Implementations of GestureDetector.OnGestureListener ----------------
+
+    /** Called whenever a gesture starts. Always accepts the gesture so it isn't ignored. */
+    @Override
+    public boolean onDown(MotionEvent e) {
+        return true;
+    }
+
+    /** Called when a fling gesture is recognized. */
+    @Override
+    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
+        if (mInputState.suppressFling()) {
+            return false;
+        }
+
+        if (mInputState.scrollFling()) {
+            mInputState.setDetectedAction(DetectedAction.AFTER_SCROLL_FLING);
+            mOnScrollFling.raise(new TwoPointsEventParameter(e1, e2, velocityX, velocityY));
+            return true;
+        }
+
+        if (mInputState.suppressCursorMovement()) {
+            return false;
+        }
+
+        mInputState.setDetectedAction(DetectedAction.FLING);
+        mOnFling.raise(new TwoPointsEventParameter(e1, e2, velocityX, velocityY));
+        return true;
+    }
+
+    /** Called when a long-press is triggered for one or more fingers. */
+    @Override
+    public void onLongPress(MotionEvent e) {}
+
+    /** Called when the user drags one or more fingers across the touchscreen. */
+    @Override
+    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
+        if (!isInPanGestureBounds(e1)) {
+            // The gesture of scrolling from edge to the center should be handled by Android OS.
+            mInputState.setDetectedAction(InputState.DetectedAction.SCROLL_EDGE);
+            return false;
+        }
+
+        if (((mSwipeWithMoreFingers && e2.getPointerCount() >= 3) || e2.getPointerCount() == 3)
+                && !mInputState.swipeCompleted()) {
+            if (distanceY > mSwipeThreshold || distanceY < -mSwipeThreshold) {
+                mInputState.setDetectedAction(DetectedAction.SWIPE);
+                mOnSwipe.raise(new TwoPointsEventParameter(e1, e2, distanceX, distanceY));
+                return true;
+            }
+            return false;
+        }
+
+        if (e2.getPointerCount() == 2 && mSwipePinchDetector.isSwiping()) {
+            mInputState.setDetectedAction(DetectedAction.SCROLL);
+            mOnScroll.raise(new TwoPointsEventParameter(e1, e2, distanceX, distanceY));
+            return true;
+        }
+
+        if (e2.getPointerCount() != 1 || mInputState.suppressCursorMovement()) {
+            return false;
+        }
+
+        mInputState.setDetectedAction(DetectedAction.MOVE);
+        mOnMove.raise(new TwoPointsEventParameter(e1, e2, distanceX, distanceY));
+        return true;
+    }
+
+    /** Called by {@link GestureDetector}, does nothing. */
+    @Override
+    public void onShowPress(MotionEvent e) {}
+
+    /** Called by {@link GestureDetector}, returns false to continue following gesture detection. */
+    @Override
+    public boolean onSingleTapUp(MotionEvent e) {
+        return false;
+    }
+
+    // --------- Implementations of ScaleGestureDetector.OnScaleGestureListener -----------
+    /** Called when the user is in the process of pinch-zooming. */
+    @Override
+    public boolean onScale(ScaleGestureDetector detector) {
+        if (!mSwipePinchDetector.isPinching()) {
+            return false;
+        }
+
+        mInputState.setDetectedAction(DetectedAction.SCALE);
+        mOnScale.raise(new ScaleEventParameter(detector.getScaleFactor(),
+                                          detector.getFocusX(),
+                                          detector.getFocusY()));
+        return true;
+    }
+
+    /**
+     * Called when the user starts to zoom. Always accepts the zoom so that
+     * onScale() can decide whether to respond to it.
+     */
+    @Override
+    public boolean onScaleBegin(ScaleGestureDetector detector) {
+        return true;
+    }
+
+    /** Called when the user is done zooming. Defers to onScale()'s judgement. */
+    @Override
+    public void onScaleEnd(ScaleGestureDetector detector) {
+        onScale(detector);
+    }
+
+    // -------------- Implementations of TapGestureDetector.OnTapListener ----------------
+    /** Called when the user taps the screen with one or more fingers. */
+    @Override
+    public boolean onTap(int pointerCount, float x, float y) {
+        TapEventParameter para = new TapEventParameter(pointerCount, x, y);
+        mOnTap.raise(para);
+        return para.handled;
+    }
+
+    /** Called when a long-press is triggered for one or more fingers. */
+    @Override
+    public void onLongPress(int pointerCount, float x, float y) {
+        TapEventParameter para = new TapEventParameter(pointerCount, x, y);
+        mOnPressAndHold.raise(para);
+        if (para.handled) {
+            mInputState.setStartAction(StartAction.LONG_PRESS);
+        }
+    }
+
+    /**
+     * Returns a boolean value to indicate whether the MotionEvent is in the range of
+     * {@link mPanGestureBounds}
+     */
+    private boolean isInPanGestureBounds(MotionEvent e) {
+        Preconditions.notNull(e);
+        return mPanGestureBounds == null
+               || mPanGestureBounds.contains((int) e.getX(), (int) e.getY());
+    }
+
+    // ---------------------------- Event handlers ---------------------------------------
+    private void handleClientSizeChanged(SizeChangedEventParameter parameter) {
+        mPanGestureBounds = new Rect(mEdgeSlopInPx,
+                                     mEdgeSlopInPx,
+                                     parameter.width - mEdgeSlopInPx,
+                                     parameter.height - mEdgeSlopInPx);
+    }
+
+    private void handleTouch(TouchEventParameter parameter) {
+        mOnTouchEvent.raise(parameter.event);
+
+        boolean handled = mScroller.onTouchEvent(parameter.event);
+        handled |= mZoomer.onTouchEvent(parameter.event);
+        handled |= mTapDetector.onTouchEvent(parameter.event);
+        mSwipePinchDetector.onTouchEvent(parameter.event);
+
+        parameter.handled = handled;
+    }
+}