core/java/android/webkit/AccessibilityInjectorFallback.java - platform/frameworks/base - Gitiles

 /*
  * Copyright (C) 2010 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 android.webkit;

 import android.os.Bundle;
 import android.provider.Settings;
 import android.text.TextUtils;
 import android.text.TextUtils.SimpleStringSplitter;
 import android.util.Log;
 import android.view.KeyEvent;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;
 import android.view.accessibility.AccessibilityNodeInfo;
 import android.webkit.WebViewCore.EventHub;

 import com.android.internal.os.SomeArgs;

 import java.util.ArrayList;

 /**
  * This class injects accessibility into WebViews with disabled JavaScript or
  * WebViews with enabled JavaScript but for which we have no accessibility
  * script to inject.
  * </p>
  * Note: To avoid changes in the framework upon changing the available
  *       navigation axis, or reordering the navigation axis, or changing
  *       the key bindings, or defining sequence of actions to be bound to
  *       a given key this class is navigation axis agnostic. It is only
  *       aware of one navigation axis which is in fact the default behavior
  *       of webViews while using the DPAD/TrackBall.
  * </p>
  * In general a key binding is a mapping from modifiers + key code to
  * a sequence of actions. For more detail how to specify key bindings refer to
  * {@link android.provider.Settings.Secure#ACCESSIBILITY_WEB_CONTENT_KEY_BINDINGS}.
  * </p>
  * The possible actions are invocations to
  * {@link #setCurrentAxis(int, boolean, String)}, or
  * {@link #traverseGivenAxis(int, int, boolean, String, boolean)}
  * {@link #performAxisTransition(int, int, boolean, String)}
  * referred via the values of:
  * {@link #ACTION_SET_CURRENT_AXIS},
  * {@link #ACTION_TRAVERSE_CURRENT_AXIS},
  * {@link #ACTION_TRAVERSE_GIVEN_AXIS},
  * {@link #ACTION_PERFORM_AXIS_TRANSITION},
  * respectively.
  * The arguments for the action invocation are specified as offset
  * hexademical pairs. Note the last argument of the invocation
  * should NOT be specified in the binding as it is provided by
  * this class. For details about the key binding implementation
  * refer to {@link AccessibilityWebContentKeyBinding}.
  */
 class AccessibilityInjectorFallback {
     private static final String LOG_TAG = "AccessibilityInjector";

     private static final boolean DEBUG = true;

     private static final int ACTION_SET_CURRENT_AXIS = 0;
     private static final int ACTION_TRAVERSE_CURRENT_AXIS = 1;
     private static final int ACTION_TRAVERSE_GIVEN_AXIS = 2;
     private static final int ACTION_PERFORM_AXIS_TRANSITION = 3;
     private static final int ACTION_TRAVERSE_DEFAULT_WEB_VIEW_BEHAVIOR_AXIS = 4;

     /** Timeout after which asynchronous granular movement is aborted. */
     private static final int MODIFY_SELECTION_TIMEOUT = 500;

     // WebView navigation axes from WebViewCore.h, plus an additional axis for
     // the default behavior.
     private static final int NAVIGATION_AXIS_CHARACTER = 0;
     private static final int NAVIGATION_AXIS_WORD = 1;
     private static final int NAVIGATION_AXIS_SENTENCE = 2;
     @SuppressWarnings("unused")
     private static final int NAVIGATION_AXIS_HEADING = 3;
     @SuppressWarnings("unused")
     private static final int NAVIGATION_AXIS_SIBLING = 4;
     @SuppressWarnings("unused")
     private static final int NAVIGATION_AXIS_PARENT_FIRST_CHILD = 5;
     private static final int NAVIGATION_AXIS_DOCUMENT = 6;
     private static final int NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR = 7;

     // WebView navigation directions from WebViewCore.h.
     private static final int NAVIGATION_DIRECTION_BACKWARD = 0;
     private static final int NAVIGATION_DIRECTION_FORWARD = 1;

     // these are the same for all instances so make them process wide
     private static ArrayList<AccessibilityWebContentKeyBinding> sBindings =
         new ArrayList<AccessibilityWebContentKeyBinding>();

     // handle to the WebViewClassic this injector is associated with.
     private final WebViewClassic mWebView;
     private final WebView mWebViewInternal;

     // Event scheduled for sending as soon as we receive the selected text.
     private AccessibilityEvent mScheduledEvent;

     // Token required to send the scheduled event.
     private int mScheduledToken = 0;

     // the current traversal axis
     private int mCurrentAxis = 2; // sentence

     // we need to consume the up if we have handled the last down
     private boolean mLastDownEventHandled;

     // getting two empty selection strings in a row we let the WebView handle the event
     private boolean mIsLastSelectionStringNull;

     // keep track of last direction
     private int mLastDirection;

     // Lock used for asynchronous selection callback.
     private final Object mCallbackLock = new Object();

     // Whether the asynchronous selection callback was received.
     private boolean mCallbackReceived;

     // Whether the asynchronous selection callback succeeded.
     private boolean mCallbackResult;

     /**
      * Creates a new injector associated with a given {@link WebViewClassic}.
      *
      * @param webView The associated WebViewClassic.
      */
     public AccessibilityInjectorFallback(WebViewClassic webView) {
         mWebView = webView;
         mWebViewInternal = mWebView.getWebView();
         ensureWebContentKeyBindings();
     }

     /**
      * Processes a key down <code>event</code>.
      *
      * @return True if the event was processed.
      */
     public boolean onKeyEvent(KeyEvent event) {
         // We do not handle ENTER in any circumstances.
         if (isEnterActionKey(event.getKeyCode())) {
             return false;
         }

         if (event.getAction() == KeyEvent.ACTION_UP) {
             return mLastDownEventHandled;
         }

         mLastDownEventHandled = false;

         AccessibilityWebContentKeyBinding binding = null;
         for (AccessibilityWebContentKeyBinding candidate : sBindings) {
             if (event.getKeyCode() == candidate.getKeyCode()
                     && event.hasModifiers(candidate.getModifiers())) {
                 binding = candidate;
                 break;
             }
         }

         if (binding == null) {
             return false;
         }

         for (int i = 0, count = binding.getActionCount(); i < count; i++) {
             int actionCode = binding.getActionCode(i);
             String contentDescription = Integer.toHexString(binding.getAction(i));
             switch (actionCode) {
                 case ACTION_SET_CURRENT_AXIS:
                     int axis = binding.getFirstArgument(i);
                     boolean sendEvent = (binding.getSecondArgument(i) == 1);
                     setCurrentAxis(axis, sendEvent, contentDescription);
                     mLastDownEventHandled = true;
                     break;
                 case ACTION_TRAVERSE_CURRENT_AXIS:
                     int direction = binding.getFirstArgument(i);
                     // on second null selection string in same direction - WebView handles the event
                     if (direction == mLastDirection && mIsLastSelectionStringNull) {
                         mIsLastSelectionStringNull = false;
                         return false;
                     }
                     mLastDirection = direction;
                     sendEvent = (binding.getSecondArgument(i) == 1);
                     mLastDownEventHandled = traverseGivenAxis(
                             direction, mCurrentAxis, sendEvent, contentDescription, false);
                     break;
                 case ACTION_TRAVERSE_GIVEN_AXIS:
                     direction = binding.getFirstArgument(i);
                     // on second null selection string in same direction => WebView handle the event
                     if (direction == mLastDirection && mIsLastSelectionStringNull) {
                         mIsLastSelectionStringNull = false;
                         return false;
                     }
                     mLastDirection = direction;
                     axis =  binding.getSecondArgument(i);
                     sendEvent = (binding.getThirdArgument(i) == 1);
                     traverseGivenAxis(direction, axis, sendEvent, contentDescription, false);
                     mLastDownEventHandled = true;
                     break;
                 case ACTION_PERFORM_AXIS_TRANSITION:
                     int fromAxis = binding.getFirstArgument(i);
                     int toAxis = binding.getSecondArgument(i);
                     sendEvent = (binding.getThirdArgument(i) == 1);
                     performAxisTransition(fromAxis, toAxis, sendEvent, contentDescription);
                     mLastDownEventHandled = true;
                     break;
                 case ACTION_TRAVERSE_DEFAULT_WEB_VIEW_BEHAVIOR_AXIS:
                     // This is a special case since we treat the default WebView navigation
                     // behavior as one of the possible navigation axis the user can use.
                     // If we are not on the default WebView navigation axis this is NOP.
                     if (mCurrentAxis == NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR) {
                         // While WebVew handles navigation we do not get null selection
                         // strings so do not check for that here as the cases above.
                         mLastDirection = binding.getFirstArgument(i);
                         sendEvent = (binding.getSecondArgument(i) == 1);
                         traverseGivenAxis(mLastDirection, NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR,
                             sendEvent, contentDescription, false);
                         mLastDownEventHandled = false;
                     } else {
                         mLastDownEventHandled = true;
                     }
                     break;
                 default:
                     Log.w(LOG_TAG, "Unknown action code: " + actionCode);
             }
         }

         return mLastDownEventHandled;
     }

     /**
      * Set the current navigation axis.
      *
      * @param axis The axis to set.
      * @param sendEvent Whether to send an accessibility event to
      *        announce the change.
      */
     private void setCurrentAxis(int axis, boolean sendEvent, String contentDescription) {
         mCurrentAxis = axis;
         if (sendEvent) {
             final AccessibilityEvent event = getPartialyPopulatedAccessibilityEvent(
                     AccessibilityEvent.TYPE_ANNOUNCEMENT);
             event.getText().add(String.valueOf(axis));
             event.setContentDescription(contentDescription);
             sendAccessibilityEvent(event);
         }
     }

     /**
      * Performs conditional transition one axis to another.
      *
      * @param fromAxis The axis which must be the current for the transition to occur.
      * @param toAxis The axis to which to transition.
      * @param sendEvent Flag if to send an event to announce successful transition.
      * @param contentDescription A description of the performed action.
      */
     private void performAxisTransition(int fromAxis, int toAxis, boolean sendEvent,
             String contentDescription) {
         if (mCurrentAxis == fromAxis) {
             setCurrentAxis(toAxis, sendEvent, contentDescription);
         }
     }

     boolean performAccessibilityAction(int action, Bundle arguments) {
         switch (action) {
             case AccessibilityNodeInfo.ACTION_NEXT_AT_MOVEMENT_GRANULARITY:
             case AccessibilityNodeInfo.ACTION_PREVIOUS_AT_MOVEMENT_GRANULARITY: {
                 final int direction = getDirectionForAction(action);
                 final int axis = getAxisForGranularity(arguments.getInt(
                         AccessibilityNodeInfo.ACTION_ARGUMENT_MOVEMENT_GRANULARITY_INT));
                 return traverseGivenAxis(direction, axis, true, null, true);
             }
             case AccessibilityNodeInfo.ACTION_NEXT_HTML_ELEMENT:
             case AccessibilityNodeInfo.ACTION_PREVIOUS_HTML_ELEMENT: {
                 final int direction = getDirectionForAction(action);
                 // TODO: Add support for moving by object.
                 final int axis = NAVIGATION_AXIS_SENTENCE;
                 return traverseGivenAxis(direction, axis, true, null, true);
             }
             default:
                 return false;
         }
     }

     /**
      * Returns the {@link WebView}-defined direction for the given
      * {@link AccessibilityNodeInfo}-defined action.
      *
      * @param action An accessibility action identifier.
      * @return A web view navigation direction.
      */
     private static int getDirectionForAction(int action) {
         switch (action) {
             case AccessibilityNodeInfo.ACTION_NEXT_HTML_ELEMENT:
             case AccessibilityNodeInfo.ACTION_NEXT_AT_MOVEMENT_GRANULARITY:
                 return NAVIGATION_DIRECTION_FORWARD;
             case AccessibilityNodeInfo.ACTION_PREVIOUS_HTML_ELEMENT:
             case AccessibilityNodeInfo.ACTION_PREVIOUS_AT_MOVEMENT_GRANULARITY:
                 return NAVIGATION_DIRECTION_BACKWARD;
             default:
                 return -1;
         }
     }

     /**
      * Returns the {@link WebView}-defined axis for the given
      * {@link AccessibilityNodeInfo}-defined granularity.
      *
      * @param granularity An accessibility granularity identifier.
      * @return A web view navigation axis.
      */
     private static int getAxisForGranularity(int granularity) {
         switch (granularity) {
             case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_CHARACTER:
                 return NAVIGATION_AXIS_CHARACTER;
             case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_WORD:
                 return NAVIGATION_AXIS_WORD;
             case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_LINE:
                 return NAVIGATION_AXIS_SENTENCE;
             case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_PARAGRAPH:
                 // TODO: This should map to object once we implement it.
                 return NAVIGATION_AXIS_SENTENCE;
             case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_PAGE:
                 return NAVIGATION_AXIS_DOCUMENT;
             default:
                 return -1;
         }
     }

     /**
      * Traverse the document along the given navigation axis.
      *
      * @param direction The direction of traversal.
      * @param axis The axis along which to traverse.
      * @param sendEvent Whether to send an accessibility event to
      *        announce the change.
      * @param contentDescription A description of the performed action.
      */
     private boolean traverseGivenAxis(int direction, int axis, boolean sendEvent,
             String contentDescription, boolean sychronous) {
         final WebViewCore webViewCore = mWebView.getWebViewCore();
         if (webViewCore == null) {
             return false;
         }

         if (sendEvent) {
             final AccessibilityEvent event = getPartialyPopulatedAccessibilityEvent(
                     AccessibilityEvent.TYPE_VIEW_TEXT_TRAVERSED_AT_MOVEMENT_GRANULARITY);
             // The text will be set upon receiving the selection string.
             event.setContentDescription(contentDescription);
             mScheduledEvent = event;
             mScheduledToken++;
         }

         // if the axis is the default let WebView handle the event which will
         // result in cursor ring movement and selection of its content
         if (axis == NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR) {
             return false;
         }

         final SomeArgs args = SomeArgs.obtain();
         args.argi1 = direction;
         args.argi2 = axis;
         args.argi3 = mScheduledToken;

         // If we don't need synchronous results, just return true.
         if (!sychronous) {
             webViewCore.sendMessage(EventHub.MODIFY_SELECTION, args);
             return true;
         }

         final boolean callbackResult;

         synchronized (mCallbackLock) {
             mCallbackReceived = false;

             // Asynchronously changes the selection in WebView, which responds by
             // calling onSelectionStringChanged().
             webViewCore.sendMessage(EventHub.MODIFY_SELECTION, args);

             try {
                 mCallbackLock.wait(MODIFY_SELECTION_TIMEOUT);
             } catch (InterruptedException e) {
                 // Do nothing.
             }

             callbackResult = mCallbackResult;
         }

         return (mCallbackReceived && callbackResult);
     }

     /* package */ void onSelectionStringChangedWebCoreThread(
             final String selection, final int token) {
         synchronized (mCallbackLock) {
             mCallbackReceived = true;
             mCallbackResult = (selection != null);
             mCallbackLock.notifyAll();
         }

         // Managing state and sending events must take place on the UI thread.
         mWebViewInternal.post(new Runnable() {
             @Override
             public void run() {
                 onSelectionStringChangedMainThread(selection, token);
             }
         });
     }

     private void onSelectionStringChangedMainThread(String selection, int token) {
         if (DEBUG) {
             Log.d(LOG_TAG, "Selection string: " + selection);
         }

         if (token != mScheduledToken) {
             if (DEBUG) {
                 Log.d(LOG_TAG, "Selection string has incorrect token: " + token);
             }
             return;
         }

         mIsLastSelectionStringNull = (selection == null);

         final AccessibilityEvent event = mScheduledEvent;
         mScheduledEvent = null;

         if ((event != null) && (selection != null)) {
             event.getText().add(selection);
             event.setFromIndex(0);
             event.setToIndex(selection.length());
             sendAccessibilityEvent(event);
         }
     }

     /**
      * Sends an {@link AccessibilityEvent}.
      *
      * @param event The event to send.
      */
     private void sendAccessibilityEvent(AccessibilityEvent event) {
         if (DEBUG) {
             Log.d(LOG_TAG, "Dispatching: " + event);
         }
         // accessibility may be disabled while waiting for the selection string
         AccessibilityManager accessibilityManager =
             AccessibilityManager.getInstance(mWebView.getContext());
         if (accessibilityManager.isEnabled()) {
             accessibilityManager.sendAccessibilityEvent(event);
         }
     }

     /**
      * @return An accessibility event whose members are populated except its
      *         text and content description.
      */
     private AccessibilityEvent getPartialyPopulatedAccessibilityEvent(int eventType) {
         AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
         mWebViewInternal.onInitializeAccessibilityEvent(event);
         return event;
     }

     /**
      * Ensures that the Web content key bindings are loaded.
      */
     private void ensureWebContentKeyBindings() {
         if (sBindings.size() > 0) {
             return;
         }

         String webContentKeyBindingsString  = Settings.Secure.getString(
                 mWebView.getContext().getContentResolver(),
                 Settings.Secure.ACCESSIBILITY_WEB_CONTENT_KEY_BINDINGS);

         SimpleStringSplitter semiColonSplitter = new SimpleStringSplitter(';');
         semiColonSplitter.setString(webContentKeyBindingsString);

         while (semiColonSplitter.hasNext()) {
             String bindingString = semiColonSplitter.next();
             if (TextUtils.isEmpty(bindingString)) {
                 Log.e(LOG_TAG, "Disregarding malformed Web content key binding: "
                         + webContentKeyBindingsString);
                 continue;
             }
             String[] keyValueArray = bindingString.split("=");
             if (keyValueArray.length != 2) {
                 Log.e(LOG_TAG, "Disregarding malformed Web content key binding: " + bindingString);
                 continue;
             }
             try {
                 long keyCodeAndModifiers = Long.decode(keyValueArray[0].trim());
                 String[] actionStrings = keyValueArray[1].split(":");
                 int[] actions = new int[actionStrings.length];
                 for (int i = 0, count = actions.length; i < count; i++) {
                     actions[i] = Integer.decode(actionStrings[i].trim());
                 }
                 sBindings.add(new AccessibilityWebContentKeyBinding(keyCodeAndModifiers, actions));
             } catch (NumberFormatException nfe) {
                 Log.e(LOG_TAG, "Disregarding malformed key binding: " + bindingString);
             }
         }
     }

     private boolean isEnterActionKey(int keyCode) {
         return keyCode == KeyEvent.KEYCODE_DPAD_CENTER
                 || keyCode == KeyEvent.KEYCODE_ENTER
                 || keyCode == KeyEvent.KEYCODE_NUMPAD_ENTER;
     }

     /**
      * Represents a web content key-binding.
      */
     private static final class AccessibilityWebContentKeyBinding {

         private static final int MODIFIERS_OFFSET = 32;
         private static final long MODIFIERS_MASK = 0xFFFFFFF00000000L;

         private static final int KEY_CODE_OFFSET = 0;
         private static final long KEY_CODE_MASK = 0x00000000FFFFFFFFL;

         private static final int ACTION_OFFSET = 24;
         private static final int ACTION_MASK = 0xFF000000;

         private static final int FIRST_ARGUMENT_OFFSET = 16;
         private static final int FIRST_ARGUMENT_MASK = 0x00FF0000;

         private static final int SECOND_ARGUMENT_OFFSET = 8;
         private static final int SECOND_ARGUMENT_MASK = 0x0000FF00;

         private static final int THIRD_ARGUMENT_OFFSET = 0;
         private static final int THIRD_ARGUMENT_MASK = 0x000000FF;

         private final long mKeyCodeAndModifiers;

         private final int [] mActionSequence;

         /**
          * @return The key code of the binding key.
          */
         public int getKeyCode() {
             return (int) ((mKeyCodeAndModifiers & KEY_CODE_MASK) >> KEY_CODE_OFFSET);
         }

         /**
          * @return The meta state of the binding key.
          */
         public int getModifiers() {
             return (int) ((mKeyCodeAndModifiers & MODIFIERS_MASK) >> MODIFIERS_OFFSET);
         }

         /**
          * @return The number of actions in the key binding.
          */
         public int getActionCount() {
             return mActionSequence.length;
         }

         /**
          * @param index The action for a given action <code>index</code>.
          */
         public int getAction(int index) {
             return mActionSequence[index];
         }

         /**
          * @param index The action code for a given action <code>index</code>.
          */
         public int getActionCode(int index) {
             return (mActionSequence[index] & ACTION_MASK) >> ACTION_OFFSET;
         }

         /**
          * @param index The first argument for a given action <code>index</code>.
          */
         public int getFirstArgument(int index) {
             return (mActionSequence[index] & FIRST_ARGUMENT_MASK) >> FIRST_ARGUMENT_OFFSET;
         }

         /**
          * @param index The second argument for a given action <code>index</code>.
          */
         public int getSecondArgument(int index) {
             return (mActionSequence[index] & SECOND_ARGUMENT_MASK) >> SECOND_ARGUMENT_OFFSET;
         }

         /**
          * @param index The third argument for a given action <code>index</code>.
          */
         public int getThirdArgument(int index) {
             return (mActionSequence[index] & THIRD_ARGUMENT_MASK) >> THIRD_ARGUMENT_OFFSET;
         }

         /**
          * Creates a new instance.
          * @param keyCodeAndModifiers The key for the binding (key and modifiers).
          * @param actionSequence The sequence of action for the binding.
          */
         public AccessibilityWebContentKeyBinding(long keyCodeAndModifiers, int[] actionSequence) {
             mKeyCodeAndModifiers = keyCodeAndModifiers;
             mActionSequence = actionSequence;
         }

         @Override
         public String toString() {
             StringBuilder builder = new StringBuilder();
             builder.append("modifiers: ");
             builder.append(getModifiers());
             builder.append(", keyCode: ");
             builder.append(getKeyCode());
             builder.append(", actions[");
             for (int i = 0, count = getActionCount(); i < count; i++) {
                 builder.append("{actionCode");
                 builder.append(i);
                 builder.append(": ");
                 builder.append(getActionCode(i));
                 builder.append(", firstArgument: ");
                 builder.append(getFirstArgument(i));
                 builder.append(", secondArgument: ");
                 builder.append(getSecondArgument(i));
                 builder.append(", thirdArgument: ");
                 builder.append(getThirdArgument(i));
                 builder.append("}");
             }
             builder.append("]");
             return builder.toString();
         }
     }
 }
	/*
	* Copyright (C) 2010 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 android.webkit;

	import android.os.Bundle;
	import android.provider.Settings;
	import android.text.TextUtils;
	import android.text.TextUtils.SimpleStringSplitter;
	import android.util.Log;
	import android.view.KeyEvent;
	import android.view.accessibility.AccessibilityEvent;
	import android.view.accessibility.AccessibilityManager;
	import android.view.accessibility.AccessibilityNodeInfo;
	import android.webkit.WebViewCore.EventHub;

	import com.android.internal.os.SomeArgs;

	import java.util.ArrayList;

	/**
	* This class injects accessibility into WebViews with disabled JavaScript or
	* WebViews with enabled JavaScript but for which we have no accessibility
	* script to inject.
	* </p>
	* Note: To avoid changes in the framework upon changing the available
	* navigation axis, or reordering the navigation axis, or changing
	* the key bindings, or defining sequence of actions to be bound to
	* a given key this class is navigation axis agnostic. It is only
	* aware of one navigation axis which is in fact the default behavior
	* of webViews while using the DPAD/TrackBall.
	* </p>
	* In general a key binding is a mapping from modifiers + key code to
	* a sequence of actions. For more detail how to specify key bindings refer to
	* {@link android.provider.Settings.Secure#ACCESSIBILITY_WEB_CONTENT_KEY_BINDINGS}.
	* </p>
	* The possible actions are invocations to
	* {@link #setCurrentAxis(int, boolean, String)}, or
	* {@link #traverseGivenAxis(int, int, boolean, String, boolean)}
	* {@link #performAxisTransition(int, int, boolean, String)}
	* referred via the values of:
	* {@link #ACTION_SET_CURRENT_AXIS},
	* {@link #ACTION_TRAVERSE_CURRENT_AXIS},
	* {@link #ACTION_TRAVERSE_GIVEN_AXIS},
	* {@link #ACTION_PERFORM_AXIS_TRANSITION},
	* respectively.
	* The arguments for the action invocation are specified as offset
	* hexademical pairs. Note the last argument of the invocation
	* should NOT be specified in the binding as it is provided by
	* this class. For details about the key binding implementation
	* refer to {@link AccessibilityWebContentKeyBinding}.
	*/
	class AccessibilityInjectorFallback {
	private static final String LOG_TAG = "AccessibilityInjector";

	private static final boolean DEBUG = true;

	private static final int ACTION_SET_CURRENT_AXIS = 0;
	private static final int ACTION_TRAVERSE_CURRENT_AXIS = 1;
	private static final int ACTION_TRAVERSE_GIVEN_AXIS = 2;
	private static final int ACTION_PERFORM_AXIS_TRANSITION = 3;
	private static final int ACTION_TRAVERSE_DEFAULT_WEB_VIEW_BEHAVIOR_AXIS = 4;

	/** Timeout after which asynchronous granular movement is aborted. */
	private static final int MODIFY_SELECTION_TIMEOUT = 500;

	// WebView navigation axes from WebViewCore.h, plus an additional axis for
	// the default behavior.
	private static final int NAVIGATION_AXIS_CHARACTER = 0;
	private static final int NAVIGATION_AXIS_WORD = 1;
	private static final int NAVIGATION_AXIS_SENTENCE = 2;
	@SuppressWarnings("unused")
	private static final int NAVIGATION_AXIS_HEADING = 3;
	@SuppressWarnings("unused")
	private static final int NAVIGATION_AXIS_SIBLING = 4;
	@SuppressWarnings("unused")
	private static final int NAVIGATION_AXIS_PARENT_FIRST_CHILD = 5;
	private static final int NAVIGATION_AXIS_DOCUMENT = 6;
	private static final int NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR = 7;

	// WebView navigation directions from WebViewCore.h.
	private static final int NAVIGATION_DIRECTION_BACKWARD = 0;
	private static final int NAVIGATION_DIRECTION_FORWARD = 1;

	// these are the same for all instances so make them process wide
	private static ArrayList<AccessibilityWebContentKeyBinding> sBindings =
	new ArrayList<AccessibilityWebContentKeyBinding>();

	// handle to the WebViewClassic this injector is associated with.
	private final WebViewClassic mWebView;
	private final WebView mWebViewInternal;

	// Event scheduled for sending as soon as we receive the selected text.
	private AccessibilityEvent mScheduledEvent;

	// Token required to send the scheduled event.
	private int mScheduledToken = 0;

	// the current traversal axis
	private int mCurrentAxis = 2; // sentence

	// we need to consume the up if we have handled the last down
	private boolean mLastDownEventHandled;

	// getting two empty selection strings in a row we let the WebView handle the event
	private boolean mIsLastSelectionStringNull;

	// keep track of last direction
	private int mLastDirection;

	// Lock used for asynchronous selection callback.
	private final Object mCallbackLock = new Object();

	// Whether the asynchronous selection callback was received.
	private boolean mCallbackReceived;

	// Whether the asynchronous selection callback succeeded.
	private boolean mCallbackResult;

	/**
	* Creates a new injector associated with a given {@link WebViewClassic}.
	*
	* @param webView The associated WebViewClassic.
	*/
	public AccessibilityInjectorFallback(WebViewClassic webView) {
	mWebView = webView;
	mWebViewInternal = mWebView.getWebView();
	ensureWebContentKeyBindings();
	}

	/**
	* Processes a key down <code>event</code>.
	*
	* @return True if the event was processed.
	*/
	public boolean onKeyEvent(KeyEvent event) {
	// We do not handle ENTER in any circumstances.
	if (isEnterActionKey(event.getKeyCode())) {
	return false;
	}

	if (event.getAction() == KeyEvent.ACTION_UP) {
	return mLastDownEventHandled;
	}

	mLastDownEventHandled = false;

	AccessibilityWebContentKeyBinding binding = null;
	for (AccessibilityWebContentKeyBinding candidate : sBindings) {
	if (event.getKeyCode() == candidate.getKeyCode()
	&& event.hasModifiers(candidate.getModifiers())) {
	binding = candidate;
	break;
	}
	}

	if (binding == null) {
	return false;
	}

	for (int i = 0, count = binding.getActionCount(); i < count; i++) {
	int actionCode = binding.getActionCode(i);
	String contentDescription = Integer.toHexString(binding.getAction(i));
	switch (actionCode) {
	case ACTION_SET_CURRENT_AXIS:
	int axis = binding.getFirstArgument(i);
	boolean sendEvent = (binding.getSecondArgument(i) == 1);
	setCurrentAxis(axis, sendEvent, contentDescription);
	mLastDownEventHandled = true;
	break;
	case ACTION_TRAVERSE_CURRENT_AXIS:
	int direction = binding.getFirstArgument(i);
	// on second null selection string in same direction - WebView handles the event
	if (direction == mLastDirection && mIsLastSelectionStringNull) {
	mIsLastSelectionStringNull = false;
	return false;
	}
	mLastDirection = direction;
	sendEvent = (binding.getSecondArgument(i) == 1);
	mLastDownEventHandled = traverseGivenAxis(
	direction, mCurrentAxis, sendEvent, contentDescription, false);
	break;
	case ACTION_TRAVERSE_GIVEN_AXIS:
	direction = binding.getFirstArgument(i);
	// on second null selection string in same direction => WebView handle the event
	if (direction == mLastDirection && mIsLastSelectionStringNull) {
	mIsLastSelectionStringNull = false;
	return false;
	}
	mLastDirection = direction;
	axis = binding.getSecondArgument(i);
	sendEvent = (binding.getThirdArgument(i) == 1);
	traverseGivenAxis(direction, axis, sendEvent, contentDescription, false);
	mLastDownEventHandled = true;
	break;
	case ACTION_PERFORM_AXIS_TRANSITION:
	int fromAxis = binding.getFirstArgument(i);
	int toAxis = binding.getSecondArgument(i);
	sendEvent = (binding.getThirdArgument(i) == 1);
	performAxisTransition(fromAxis, toAxis, sendEvent, contentDescription);
	mLastDownEventHandled = true;
	break;
	case ACTION_TRAVERSE_DEFAULT_WEB_VIEW_BEHAVIOR_AXIS:
	// This is a special case since we treat the default WebView navigation
	// behavior as one of the possible navigation axis the user can use.
	// If we are not on the default WebView navigation axis this is NOP.
	if (mCurrentAxis == NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR) {
	// While WebVew handles navigation we do not get null selection
	// strings so do not check for that here as the cases above.
	mLastDirection = binding.getFirstArgument(i);
	sendEvent = (binding.getSecondArgument(i) == 1);
	traverseGivenAxis(mLastDirection, NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR,
	sendEvent, contentDescription, false);
	mLastDownEventHandled = false;
	} else {
	mLastDownEventHandled = true;
	}
	break;
	default:
	Log.w(LOG_TAG, "Unknown action code: " + actionCode);
	}
	}

	return mLastDownEventHandled;
	}

	/**
	* Set the current navigation axis.
	*
	* @param axis The axis to set.
	* @param sendEvent Whether to send an accessibility event to
	* announce the change.
	*/
	private void setCurrentAxis(int axis, boolean sendEvent, String contentDescription) {
	mCurrentAxis = axis;
	if (sendEvent) {
	final AccessibilityEvent event = getPartialyPopulatedAccessibilityEvent(
	AccessibilityEvent.TYPE_ANNOUNCEMENT);
	event.getText().add(String.valueOf(axis));
	event.setContentDescription(contentDescription);
	sendAccessibilityEvent(event);
	}
	}

	/**
	* Performs conditional transition one axis to another.
	*
	* @param fromAxis The axis which must be the current for the transition to occur.
	* @param toAxis The axis to which to transition.
	* @param sendEvent Flag if to send an event to announce successful transition.
	* @param contentDescription A description of the performed action.
	*/
	private void performAxisTransition(int fromAxis, int toAxis, boolean sendEvent,
	String contentDescription) {
	if (mCurrentAxis == fromAxis) {
	setCurrentAxis(toAxis, sendEvent, contentDescription);
	}
	}

	boolean performAccessibilityAction(int action, Bundle arguments) {
	switch (action) {
	case AccessibilityNodeInfo.ACTION_NEXT_AT_MOVEMENT_GRANULARITY:
	case AccessibilityNodeInfo.ACTION_PREVIOUS_AT_MOVEMENT_GRANULARITY: {
	final int direction = getDirectionForAction(action);
	final int axis = getAxisForGranularity(arguments.getInt(
	AccessibilityNodeInfo.ACTION_ARGUMENT_MOVEMENT_GRANULARITY_INT));
	return traverseGivenAxis(direction, axis, true, null, true);
	}
	case AccessibilityNodeInfo.ACTION_NEXT_HTML_ELEMENT:
	case AccessibilityNodeInfo.ACTION_PREVIOUS_HTML_ELEMENT: {
	final int direction = getDirectionForAction(action);
	// TODO: Add support for moving by object.
	final int axis = NAVIGATION_AXIS_SENTENCE;
	return traverseGivenAxis(direction, axis, true, null, true);
	}
	default:
	return false;
	}
	}

	/**
	* Returns the {@link WebView}-defined direction for the given
	* {@link AccessibilityNodeInfo}-defined action.
	*
	* @param action An accessibility action identifier.
	* @return A web view navigation direction.
	*/
	private static int getDirectionForAction(int action) {
	switch (action) {
	case AccessibilityNodeInfo.ACTION_NEXT_HTML_ELEMENT:
	case AccessibilityNodeInfo.ACTION_NEXT_AT_MOVEMENT_GRANULARITY:
	return NAVIGATION_DIRECTION_FORWARD;
	case AccessibilityNodeInfo.ACTION_PREVIOUS_HTML_ELEMENT:
	case AccessibilityNodeInfo.ACTION_PREVIOUS_AT_MOVEMENT_GRANULARITY:
	return NAVIGATION_DIRECTION_BACKWARD;
	default:
	return -1;
	}
	}

	/**
	* Returns the {@link WebView}-defined axis for the given
	* {@link AccessibilityNodeInfo}-defined granularity.
	*
	* @param granularity An accessibility granularity identifier.
	* @return A web view navigation axis.
	*/
	private static int getAxisForGranularity(int granularity) {
	switch (granularity) {
	case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_CHARACTER:
	return NAVIGATION_AXIS_CHARACTER;
	case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_WORD:
	return NAVIGATION_AXIS_WORD;
	case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_LINE:
	return NAVIGATION_AXIS_SENTENCE;
	case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_PARAGRAPH:
	// TODO: This should map to object once we implement it.
	return NAVIGATION_AXIS_SENTENCE;
	case AccessibilityNodeInfo.MOVEMENT_GRANULARITY_PAGE:
	return NAVIGATION_AXIS_DOCUMENT;
	default:
	return -1;
	}
	}

	/**
	* Traverse the document along the given navigation axis.
	*
	* @param direction The direction of traversal.
	* @param axis The axis along which to traverse.
	* @param sendEvent Whether to send an accessibility event to
	* announce the change.
	* @param contentDescription A description of the performed action.
	*/
	private boolean traverseGivenAxis(int direction, int axis, boolean sendEvent,
	String contentDescription, boolean sychronous) {
	final WebViewCore webViewCore = mWebView.getWebViewCore();
	if (webViewCore == null) {
	return false;
	}

	if (sendEvent) {
	final AccessibilityEvent event = getPartialyPopulatedAccessibilityEvent(
	AccessibilityEvent.TYPE_VIEW_TEXT_TRAVERSED_AT_MOVEMENT_GRANULARITY);
	// The text will be set upon receiving the selection string.
	event.setContentDescription(contentDescription);
	mScheduledEvent = event;
	mScheduledToken++;
	}

	// if the axis is the default let WebView handle the event which will
	// result in cursor ring movement and selection of its content
	if (axis == NAVIGATION_AXIS_DEFAULT_WEB_VIEW_BEHAVIOR) {
	return false;
	}

	final SomeArgs args = SomeArgs.obtain();
	args.argi1 = direction;
	args.argi2 = axis;
	args.argi3 = mScheduledToken;

	// If we don't need synchronous results, just return true.
	if (!sychronous) {
	webViewCore.sendMessage(EventHub.MODIFY_SELECTION, args);
	return true;
	}

	final boolean callbackResult;

	synchronized (mCallbackLock) {
	mCallbackReceived = false;

	// Asynchronously changes the selection in WebView, which responds by
	// calling onSelectionStringChanged().
	webViewCore.sendMessage(EventHub.MODIFY_SELECTION, args);

	try {
	mCallbackLock.wait(MODIFY_SELECTION_TIMEOUT);
	} catch (InterruptedException e) {
	// Do nothing.
	}

	callbackResult = mCallbackResult;
	}

	return (mCallbackReceived && callbackResult);
	}

	/* package */ void onSelectionStringChangedWebCoreThread(
	final String selection, final int token) {
	synchronized (mCallbackLock) {
	mCallbackReceived = true;
	mCallbackResult = (selection != null);
	mCallbackLock.notifyAll();
	}

	// Managing state and sending events must take place on the UI thread.
	mWebViewInternal.post(new Runnable() {
	@Override
	public void run() {
	onSelectionStringChangedMainThread(selection, token);
	}
	});
	}

	private void onSelectionStringChangedMainThread(String selection, int token) {
	if (DEBUG) {
	Log.d(LOG_TAG, "Selection string: " + selection);
	}

	if (token != mScheduledToken) {
	if (DEBUG) {
	Log.d(LOG_TAG, "Selection string has incorrect token: " + token);
	}
	return;
	}

	mIsLastSelectionStringNull = (selection == null);

	final AccessibilityEvent event = mScheduledEvent;
	mScheduledEvent = null;

	if ((event != null) && (selection != null)) {
	event.getText().add(selection);
	event.setFromIndex(0);
	event.setToIndex(selection.length());
	sendAccessibilityEvent(event);
	}
	}

	/**
	* Sends an {@link AccessibilityEvent}.
	*
	* @param event The event to send.
	*/
	private void sendAccessibilityEvent(AccessibilityEvent event) {
	if (DEBUG) {
	Log.d(LOG_TAG, "Dispatching: " + event);
	}
	// accessibility may be disabled while waiting for the selection string
	AccessibilityManager accessibilityManager =
	AccessibilityManager.getInstance(mWebView.getContext());
	if (accessibilityManager.isEnabled()) {
	accessibilityManager.sendAccessibilityEvent(event);
	}
	}

	/**
	* @return An accessibility event whose members are populated except its
	* text and content description.
	*/
	private AccessibilityEvent getPartialyPopulatedAccessibilityEvent(int eventType) {
	AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
	mWebViewInternal.onInitializeAccessibilityEvent(event);
	return event;
	}

	/**
	* Ensures that the Web content key bindings are loaded.
	*/
	private void ensureWebContentKeyBindings() {
	if (sBindings.size() > 0) {
	return;
	}

	String webContentKeyBindingsString = Settings.Secure.getString(
	mWebView.getContext().getContentResolver(),
	Settings.Secure.ACCESSIBILITY_WEB_CONTENT_KEY_BINDINGS);

	SimpleStringSplitter semiColonSplitter = new SimpleStringSplitter(';');
	semiColonSplitter.setString(webContentKeyBindingsString);

	while (semiColonSplitter.hasNext()) {
	String bindingString = semiColonSplitter.next();
	if (TextUtils.isEmpty(bindingString)) {
	Log.e(LOG_TAG, "Disregarding malformed Web content key binding: "
	+ webContentKeyBindingsString);
	continue;
	}
	String[] keyValueArray = bindingString.split("=");
	if (keyValueArray.length != 2) {
	Log.e(LOG_TAG, "Disregarding malformed Web content key binding: " + bindingString);
	continue;
	}
	try {
	long keyCodeAndModifiers = Long.decode(keyValueArray[0].trim());
	String[] actionStrings = keyValueArray[1].split(":");
	int[] actions = new int[actionStrings.length];
	for (int i = 0, count = actions.length; i < count; i++) {
	actions[i] = Integer.decode(actionStrings[i].trim());
	}
	sBindings.add(new AccessibilityWebContentKeyBinding(keyCodeAndModifiers, actions));
	} catch (NumberFormatException nfe) {
	Log.e(LOG_TAG, "Disregarding malformed key binding: " + bindingString);
	}
	}
	}

	private boolean isEnterActionKey(int keyCode) {
	return keyCode == KeyEvent.KEYCODE_DPAD_CENTER
	\|\| keyCode == KeyEvent.KEYCODE_ENTER
	\|\| keyCode == KeyEvent.KEYCODE_NUMPAD_ENTER;
	}

	/**
	* Represents a web content key-binding.
	*/
	private static final class AccessibilityWebContentKeyBinding {

	private static final int MODIFIERS_OFFSET = 32;
	private static final long MODIFIERS_MASK = 0xFFFFFFF00000000L;

	private static final int KEY_CODE_OFFSET = 0;
	private static final long KEY_CODE_MASK = 0x00000000FFFFFFFFL;

	private static final int ACTION_OFFSET = 24;
	private static final int ACTION_MASK = 0xFF000000;

	private static final int FIRST_ARGUMENT_OFFSET = 16;
	private static final int FIRST_ARGUMENT_MASK = 0x00FF0000;

	private static final int SECOND_ARGUMENT_OFFSET = 8;
	private static final int SECOND_ARGUMENT_MASK = 0x0000FF00;

	private static final int THIRD_ARGUMENT_OFFSET = 0;
	private static final int THIRD_ARGUMENT_MASK = 0x000000FF;

	private final long mKeyCodeAndModifiers;

	private final int [] mActionSequence;

	/**
	* @return The key code of the binding key.
	*/
	public int getKeyCode() {
	return (int) ((mKeyCodeAndModifiers & KEY_CODE_MASK) >> KEY_CODE_OFFSET);
	}

	/**
	* @return The meta state of the binding key.
	*/
	public int getModifiers() {
	return (int) ((mKeyCodeAndModifiers & MODIFIERS_MASK) >> MODIFIERS_OFFSET);
	}

	/**
	* @return The number of actions in the key binding.
	*/
	public int getActionCount() {
	return mActionSequence.length;
	}

	/**
	* @param index The action for a given action <code>index</code>.
	*/
	public int getAction(int index) {
	return mActionSequence[index];
	}

	/**
	* @param index The action code for a given action <code>index</code>.
	*/
	public int getActionCode(int index) {
	return (mActionSequence[index] & ACTION_MASK) >> ACTION_OFFSET;
	}

	/**
	* @param index The first argument for a given action <code>index</code>.
	*/
	public int getFirstArgument(int index) {
	return (mActionSequence[index] & FIRST_ARGUMENT_MASK) >> FIRST_ARGUMENT_OFFSET;
	}

	/**
	* @param index The second argument for a given action <code>index</code>.
	*/
	public int getSecondArgument(int index) {
	return (mActionSequence[index] & SECOND_ARGUMENT_MASK) >> SECOND_ARGUMENT_OFFSET;
	}

	/**
	* @param index The third argument for a given action <code>index</code>.
	*/
	public int getThirdArgument(int index) {
	return (mActionSequence[index] & THIRD_ARGUMENT_MASK) >> THIRD_ARGUMENT_OFFSET;
	}

	/**
	* Creates a new instance.
	* @param keyCodeAndModifiers The key for the binding (key and modifiers).
	* @param actionSequence The sequence of action for the binding.
	*/
	public AccessibilityWebContentKeyBinding(long keyCodeAndModifiers, int[] actionSequence) {
	mKeyCodeAndModifiers = keyCodeAndModifiers;
	mActionSequence = actionSequence;
	}

	@Override
	public String toString() {
	StringBuilder builder = new StringBuilder();
	builder.append("modifiers: ");
	builder.append(getModifiers());
	builder.append(", keyCode: ");
	builder.append(getKeyCode());
	builder.append(", actions[");
	for (int i = 0, count = getActionCount(); i < count; i++) {
	builder.append("{actionCode");
	builder.append(i);
	builder.append(": ");
	builder.append(getActionCode(i));
	builder.append(", firstArgument: ");
	builder.append(getFirstArgument(i));
	builder.append(", secondArgument: ");
	builder.append(getSecondArgument(i));
	builder.append(", thirdArgument: ");
	builder.append(getThirdArgument(i));
	builder.append("}");
	}
	builder.append("]");
	return builder.toString();
	}
	}
	}