path: root/remoting/android/java/src/org/chromium/chromoting/TouchInputStrategy.java

// Copyright 2015 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.graphics.Matrix;
import android.view.MotionEvent;

import org.chromium.base.VisibleForTesting;
import org.chromium.chromoting.jni.JniInterface;
import org.chromium.chromoting.jni.TouchEventData;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * This class receives local touch input events and forwards them to the remote host.
 * A queue of MotionEvents is built up and then either transmitted to the remote host if one of its
 * remote gesture handler methods is called (such as onScroll) or it is cleared if the current
 * stream of events does not represent a remote gesture.
 * NOTE: Not all touch gestures are remoted.  Touch input and gestures outside the supported ones
 *       (which includes tapping and 2 finger panning) will either affect the local canvas or
 *       will be dropped/ignored.
 */
public class TouchInputStrategy implements InputStrategyInterface {
    /**
     * This interface abstracts the injection mechanism to allow for unit testing.
     */
    public interface RemoteInputInjector {
        public void injectMouseEvent(int x, int y, int button, boolean buttonDown);
        public void injectTouchEvent(TouchEventData.EventType eventType, TouchEventData[] data);
    }

    /**
     * This class provides the default implementation for injecting remote events.
     */
    private static class DefaultInputInjector implements RemoteInputInjector {
        @Override
        public void injectMouseEvent(int x, int y, int button, boolean buttonDown) {
            JniInterface.sendMouseEvent(x, y, button, buttonDown);
        }

        @Override
        public void injectTouchEvent(TouchEventData.EventType eventType, TouchEventData[] data) {
            JniInterface.sendTouchEvent(eventType, data);
        }
    }

    /**
     * Contains the maximum number of MotionEvents to store before cancelling the current gesture.
     * The size is ~3x the largest number of events seen during any remotable gesture sequence.
     */
    private static final int QUEUED_EVENT_THRESHOLD = 50;

    /**
     * Contains the set of MotionEvents received for the current gesture candidate.  If one of the
     * gesture handling methods is called, these queued events will be transmitted to the remote
     * host for injection.  The queue has a maximum size determined by |QUEUED_EVENT_THRESHOLD| to
     * prevent a live memory leak where the queue grows unbounded during a local gesture (such as
     * someone panning the local canvas continuously for several seconds/minutes).
     */
    private Queue<MotionEvent> mQueuedEvents;

    /**
     * Indicates that the events received should be treated as part of an active remote gesture.
     */
    private boolean mInRemoteGesture = false;

    /**
     * Indicates whether MotionEvents and gestures should be acted upon or ignored.  This flag is
     * set when we believe that the current sequence of events is not something we should remote.
     */
    private boolean mIgnoreTouchEvents = false;

    private final RenderData mRenderData;

    private RemoteInputInjector mRemoteInputInjector;

    public TouchInputStrategy(RenderData renderData) {
        mRenderData = renderData;
        mRemoteInputInjector = new DefaultInputInjector();
        mQueuedEvents = new LinkedList<MotionEvent>();

        synchronized (mRenderData) {
            mRenderData.drawCursor = false;
        }
    }

    @Override
    public boolean onTap(int button) {
        if (mQueuedEvents.isEmpty() || mIgnoreTouchEvents) {
            return false;
        }

        switch (button) {
            case TouchInputHandlerInterface.BUTTON_LEFT:
                injectQueuedEvents();
                return true;

            case TouchInputHandlerInterface.BUTTON_RIGHT:
                // Using the mouse for right-clicking is consistent across all host platforms.
                // Right-click gestures are often platform specific and can be tricky to simulate.

                // Grab the first queued event which should be the initial ACTION_DOWN event.
                MotionEvent downEvent = mQueuedEvents.peek();
                assert downEvent.getActionMasked() == MotionEvent.ACTION_DOWN;

                int x = (int) downEvent.getX();
                int y = (int) downEvent.getY();
                mRemoteInputInjector.injectMouseEvent(
                        x, y, TouchInputHandlerInterface.BUTTON_RIGHT, true);
                mRemoteInputInjector.injectMouseEvent(
                        x, y, TouchInputHandlerInterface.BUTTON_RIGHT, false);
                clearQueuedEvents();
                return true;

            default:
                // Tap gestures for > 2 fingers are not supported.
                return false;
        }
    }

    @Override
    public boolean onPressAndHold(int button) {
        if (button != TouchInputHandlerInterface.BUTTON_LEFT || mQueuedEvents.isEmpty()
                || mIgnoreTouchEvents) {
            return false;
        }

        mInRemoteGesture = true;
        injectQueuedEvents();
        return true;
    }

    @Override
    public void onScroll(float distanceX, float distanceY) {
        if (mIgnoreTouchEvents || mInRemoteGesture) {
            return;
        }

        mInRemoteGesture = true;
        injectQueuedEvents();
    }

    @Override
    public void onMotionEvent(MotionEvent event) {
        // MotionEvents received are stored in a queue.  This queue is added to until one of the
        // gesture handling methods is called to indicate that a remote gesture is in progress.  At
        // that point, each enqueued MotionEvent is dequeued and transmitted to the remote machine
        // and the class will now forward all MotionEvents received in real time until the gesture
        // has been completed.  If we receive too many events without having been notified to start
        // a remote gesture, then the queue is cleared and we will wait until the start of the next
        // gesture to begin queueing again.
        int action = event.getActionMasked();
        if (mIgnoreTouchEvents && action != MotionEvent.ACTION_DOWN) {
            return;
        } else if (mQueuedEvents.size() > QUEUED_EVENT_THRESHOLD) {
            // Since we maintain a queue of events to replay once the gesture is known, we need to
            // ensure that we do not continue to queue events when we are reasonably sure that the
            // user action is not going to be sent to the remote host.
            mIgnoreTouchEvents = true;
            clearQueuedEvents();
            return;
        }

        switch (action) {
            case MotionEvent.ACTION_DOWN:
                resetStateData();
                mQueuedEvents.add(transformToRemoteCoordinates(event));
                break;

            case MotionEvent.ACTION_POINTER_DOWN:
                if (mInRemoteGesture) {
                    // Cancel the current gesture if a pointer down action is seen during it.
                    // We do this because a new pointer down means that we are no longer performing
                    // the old gesture.
                    mIgnoreTouchEvents = true;
                    clearQueuedEvents();
                } else {
                    mQueuedEvents.add(transformToRemoteCoordinates(event));
                }
                break;

            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_MOVE:
            case MotionEvent.ACTION_POINTER_UP:
            case MotionEvent.ACTION_UP:
                event = transformToRemoteCoordinates(event);
                if (mInRemoteGesture) {
                    injectTouchEventData(event);
                    event.recycle();
                } else {
                    mQueuedEvents.add(event);
                }
                break;

            default:
                break;
        }
    }

    @Override
    public void injectCursorMoveEvent(int x, int y) {}

    @Override
    public DesktopView.InputFeedbackType getShortPressFeedbackType() {
        return DesktopView.InputFeedbackType.NONE;
    }

    @Override
    public DesktopView.InputFeedbackType getLongPressFeedbackType() {
        return DesktopView.InputFeedbackType.LARGE_ANIMATION;
    }

    @Override
    public boolean isIndirectInputMode() {
        return false;
    }

    @VisibleForTesting
    protected void setRemoteInputInjectorForTest(RemoteInputInjector injector) {
        mRemoteInputInjector = injector;
    }

    /**
     * Extracts the touch point data from a MotionEvent, converts each point into a marshallable
     * object and passes the set of points to the JNI layer to be transmitted to the remote host.
     *
     * @param event The event to send to the remote host for injection.  NOTE: This object must be
     *              updated to represent the remote machine's coordinate system before calling this
     *              function.  This should be done via the transformToRemoteCoordinates() method.
     */
    private void injectTouchEventData(MotionEvent event) {
        int action = event.getActionMasked();
        TouchEventData.EventType touchEventType = TouchEventData.EventType.fromMaskedAction(action);
        List<TouchEventData> touchEventList = new ArrayList<TouchEventData>();

        if (action == MotionEvent.ACTION_MOVE) {
            // In order to process all of the events associated with an ACTION_MOVE event, we need
            // to walk the list of historical events in order and add each event to our list, then
            // retrieve the current move event data.
            int pointerCount = event.getPointerCount();
            int historySize = event.getHistorySize();
            for (int h = 0; h < historySize; ++h) {
                for (int p = 0; p < pointerCount; ++p) {
                    touchEventList.add(new TouchEventData(event.getPointerId(p),
                            event.getHistoricalX(p, h), event.getHistoricalY(p, h),
                            event.getHistoricalSize(p, h), event.getHistoricalSize(p, h),
                            event.getHistoricalOrientation(p, h),
                            event.getHistoricalPressure(p, h)));
                }
            }

            for (int p = 0; p < pointerCount; p++) {
                touchEventList.add(new TouchEventData(event.getPointerId(p), event.getX(p),
                        event.getY(p), event.getSize(p), event.getSize(p), event.getOrientation(p),
                        event.getPressure(p)));
            }
        } else {
            // For all other events, we only want to grab the current/active pointer.  The event
            // contains a list of every active pointer but passing all of of these to the host can
            // cause confusion on the remote OS side and result in broken touch gestures.
            int activePointerIndex = event.getActionIndex();
            touchEventList.add(new TouchEventData(event.getPointerId(activePointerIndex),
                    event.getX(activePointerIndex), event.getY(activePointerIndex),
                    event.getSize(activePointerIndex), event.getSize(activePointerIndex),
                    event.getOrientation(activePointerIndex),
                    event.getPressure(activePointerIndex)));
        }

        if (!touchEventList.isEmpty()) {
            TouchEventData[] touchEventArray = new TouchEventData[touchEventList.size()];
            mRemoteInputInjector.injectTouchEvent(
                    touchEventType, touchEventList.toArray(touchEventArray));
        }
    }

    private void injectQueuedEvents() {
        while (!mQueuedEvents.isEmpty()) {
            MotionEvent event = mQueuedEvents.remove();
            injectTouchEventData(event);
            event.recycle();
        }
    }

    private void clearQueuedEvents() {
        while (!mQueuedEvents.isEmpty()) {
            mQueuedEvents.remove().recycle();
        }
    }

    // NOTE: MotionEvents generated from this method should be recycled.
    private MotionEvent transformToRemoteCoordinates(MotionEvent event) {
        // Use a copy of the original event so the original event can be passed to other
        // detectors/handlers in an unmodified state.
        event = MotionEvent.obtain(event);
        synchronized (mRenderData) {
            // Transform the event coordinates so they represent the remote screen coordinates
            // instead of the local touch display.
            Matrix inverted = new Matrix();
            mRenderData.transform.invert(inverted);
            event.transform(inverted);
        }

        return event;
    }

    private void resetStateData() {
        clearQueuedEvents();
        mInRemoteGesture = false;
        mIgnoreTouchEvents = false;
    }
}