Added text navigation gestures for keyboard touch exploration.

Bug: 4905427
Change-Id: I9b44d65e4503e46ce71322a3c325c55d188e34a0

1 files changed, 227 insertions, 0 deletions

diff --git a/java/src/com/android/inputmethod/accessibility/FlickGestureDetector.java b/java/src/com/android/inputmethod/accessibility/FlickGestureDetector.java
new file mode 100644
index 000000000..9d99e3131
--- /dev/null
+++ b/java/src/com/android/inputmethod/accessibility/FlickGestureDetector.java
@@ -0,0 +1,227 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.inputmethod.accessibility;
+
+import android.content.Context;
+import android.os.Message;
+import android.view.MotionEvent;
+import android.view.ViewConfiguration;
+
+import com.android.inputmethod.compat.MotionEventCompatUtils;
+import com.android.inputmethod.keyboard.PointerTracker;
+import com.android.inputmethod.latin.StaticInnerHandlerWrapper;
+
+/**
+ * Detects flick gestures within a stream of hover events.
+ * <p>
+ * A flick gesture is defined as a stream of hover events with the following
+ * properties:
+ * <ul>
+ *   <li>Begins with a {@link MotionEventCompatUtils#ACTION_HOVER_ENTER} event
+ *   <li>Contains any number of {@link MotionEventCompatUtils#ACTION_HOVER_MOVE}
+ *       events
+ *   <li>Ends with a {@link MotionEventCompatUtils#ACTION_HOVER_EXIT} event
+ *   <li>Maximum duration of 250 milliseconds
+ *   <li>Minimum distance between enter and exit points must be at least equal to
+ *       scaled double tap slop (see
+ *       {@link ViewConfiguration#getScaledDoubleTapSlop()})
+ * </ul>
+ * <p>
+ * Initial enter events are intercepted and cached until the stream fails to
+ * satisfy the constraints defined above, at which point the cached enter event
+ * is sent to its source {@link AccessibleKeyboardViewProxy} and subsequent move
+ * and exit events are ignored.
+ */
+public abstract class FlickGestureDetector {
+    public static final int FLICK_UP = 0;
+    public static final int FLICK_RIGHT = 1;
+    public static final int FLICK_LEFT = 2;
+    public static final int FLICK_DOWN = 3;
+
+    private final FlickHandler mFlickHandler;
+    private final int mFlickRadiusSquare;
+
+    private AccessibleKeyboardViewProxy mCachedView;
+    private PointerTracker mCachedTracker;
+    private MotionEvent mCachedHoverEnter;
+
+    private static class FlickHandler extends StaticInnerHandlerWrapper<FlickGestureDetector> {
+        private static final int MSG_FLICK_TIMEOUT = 1;
+
+        /** The maximum duration of a flick gesture in milliseconds. */
+        private static final int DELAY_FLICK_TIMEOUT = 250;
+
+        public FlickHandler(FlickGestureDetector outerInstance) {
+            super(outerInstance);
+        }
+
+        @Override
+        public void handleMessage(Message msg) {
+            final FlickGestureDetector gestureDetector = getOuterInstance();
+
+            switch (msg.what) {
+            case MSG_FLICK_TIMEOUT:
+                gestureDetector.clearFlick(true);
+            }
+        }
+
+        public void startFlickTimeout() {
+            cancelFlickTimeout();
+            sendEmptyMessageDelayed(MSG_FLICK_TIMEOUT, DELAY_FLICK_TIMEOUT);
+        }
+
+        public void cancelFlickTimeout() {
+            removeMessages(MSG_FLICK_TIMEOUT);
+        }
+    }
+
+    /**
+     * Creates a new flick gesture detector.
+     *
+     * @param context The parent context.
+     */
+    public FlickGestureDetector(Context context) {
+        final int doubleTapSlop = ViewConfiguration.get(context).getScaledDoubleTapSlop();
+
+        mFlickHandler = new FlickHandler(this);
+        mFlickRadiusSquare = doubleTapSlop * doubleTapSlop;
+    }
+
+    /**
+     * Processes motion events to detect flick gestures.
+     *
+     * @param event The current event.
+     * @param view The source of the event.
+     * @param tracker A pointer tracker for the event.
+     * @return {@code true} if the event was handled.
+     */
+    public boolean onHoverEvent(MotionEvent event, AccessibleKeyboardViewProxy view,
+            PointerTracker tracker) {
+        // Always cache and consume the first hover event.
+        if (event.getAction() == MotionEventCompatUtils.ACTION_HOVER_ENTER) {
+            mCachedView = view;
+            mCachedTracker = tracker;
+            mCachedHoverEnter = MotionEvent.obtain(event);
+            mFlickHandler.startFlickTimeout();
+            return true;
+        }
+
+        // Stop if the event has already been canceled.
+        if (mCachedHoverEnter == null) {
+            return false;
+        }
+
+        final float distanceSquare = calculateDistanceSquare(mCachedHoverEnter, event);
+        final long timeout = event.getEventTime() - mCachedHoverEnter.getEventTime();
+
+        switch (event.getAction()) {
+        case MotionEventCompatUtils.ACTION_HOVER_MOVE:
+            // Consume all valid move events before timeout.
+            return true;
+        case MotionEventCompatUtils.ACTION_HOVER_EXIT:
+            // Ignore exit events outside the flick radius.
+            if (distanceSquare < mFlickRadiusSquare) {
+                clearFlick(true);
+                return false;
+            } else {
+                return dispatchFlick(mCachedHoverEnter, event);
+            }
+        default:
+            return false;
+        }
+    }
+
+    /**
+     * Clears the cached flick information and optionally forwards the event to
+     * the source view's internal hover event handler.
+     *
+     * @param sendCachedEvent Set to {@code true} to forward the hover event to
+     *            the source view.
+     */
+    private void clearFlick(boolean sendCachedEvent) {
+        mFlickHandler.cancelFlickTimeout();
+
+        if (mCachedHoverEnter != null) {
+            if (sendCachedEvent) {
+                mCachedView.onHoverEventInternal(mCachedHoverEnter, mCachedTracker);
+            }
+            mCachedHoverEnter.recycle();
+            mCachedHoverEnter = null;
+        }
+
+        mCachedTracker = null;
+        mCachedView = null;
+    }
+
+    /**
+     * Computes the direction of a flick gesture and forwards it to
+     * {@link #onFlick(MotionEvent, MotionEvent, int)} for handling.
+     *
+     * @param e1 The {@link MotionEventCompatUtils#ACTION_HOVER_ENTER} event
+     *            where the flick started.
+     * @param e2 The {@link MotionEventCompatUtils#ACTION_HOVER_EXIT} event
+     *            where the flick ended.
+     * @return {@code true} if the flick event was handled.
+     */
+    private boolean dispatchFlick(MotionEvent e1, MotionEvent e2) {
+        clearFlick(false);
+
+        final float dX = e2.getX() - e1.getX();
+        final float dY = e2.getY() - e1.getY();
+        final int direction;
+
+        if (dY > dX) {
+            if (dY > -dX) {
+                direction = FLICK_DOWN;
+            } else {
+                direction = FLICK_LEFT;
+            }
+        } else {
+            if (dY > -dX) {
+                direction = FLICK_RIGHT;
+            } else {
+                direction = FLICK_UP;
+            }
+        }
+
+        return onFlick(e1, e2, direction);
+    }
+
+    private float calculateDistanceSquare(MotionEvent e1, MotionEvent e2) {
+        final float dX = e2.getX() - e1.getX();
+        final float dY = e2.getY() - e1.getY();
+        return (dX * dX) + (dY * dY);
+    }
+
+    /**
+     * Handles a detected flick gesture.
+     *
+     * @param e1 The {@link MotionEventCompatUtils#ACTION_HOVER_ENTER} event
+     *            where the flick started.
+     * @param e2 The {@link MotionEventCompatUtils#ACTION_HOVER_EXIT} event
+     *            where the flick ended.
+     * @param direction The direction of the flick event, one of:
+     *            <ul>
+     *              <li>{@link #FLICK_UP}
+     *              <li>{@link #FLICK_DOWN}
+     *              <li>{@link #FLICK_LEFT}
+     *              <li>{@link #FLICK_RIGHT}
+     *            </ul>
+     * @return {@code true} if the flick event was handled.
+     */
+    public abstract boolean onFlick(MotionEvent e1, MotionEvent e2, int direction);
+}