Touch exploration feature, event bubling, refactor

1. Added an Input Filter that interprets the touch screen motion
   events to perfrom accessibility exploration. One finger explores.
   Tapping within a given time and distance slop on the last exlopred
   location does click and long press, respectively. Two fingers close
   and in the same diretion drag. Multiple finglers or two fingers in
   different directions or two fingers too far away are delegated to
   the view hierarchy. Non moving fingers "accidentally grabbed the
   device for the scrren" are ignored.

2. Added accessibility events for hover enter, hover exit, touch
   exoloration gesture start, and end. Accessibility hover events
   are fired by the hover pipeline. An accessibility event is
   dispatched up the view tree and the topmost view fires it.
   Thus predecessors can augment the fired event. An accessibility
   event has several records and a predecessor can optionally
   modify, delete, and add such to the event.

3. Added onPopulateAccessibilityEvent and refactored the existing
   accessibility code to use it.

4. Added API for querying the currently enabled accessibility services
   by feedback type.

Change-Id: Iea2258c07ffae9491071825d966dc453b07e5134

1 files changed, 21 insertions, 1 deletions

diff --git a/core/java/android/view/ViewConfiguration.java b/core/java/android/view/ViewConfiguration.java
index 739758c8c79f..94eb429dad64 100644
--- a/core/java/android/view/ViewConfiguration.java
+++ b/core/java/android/view/ViewConfiguration.java
@@ -19,7 +19,6 @@ package android.view;
 import android.app.AppGlobals;
 import android.content.Context;
 import android.content.res.Configuration;
-import android.os.Bundle;
 import android.provider.Settings;
 import android.util.DisplayMetrics;
 import android.util.SparseArray;
@@ -156,6 +155,13 @@ public class ViewConfiguration {
     private static final int MAXIMUM_FLING_VELOCITY = 8000;
 
     /**
+     * Distance between a touch up event denoting the end of a touch exploration
+     * gesture and the touch up event of a subsequent tap for the latter tap to be
+     * considered as a tap i.e. to perform a click.
+     */
+    private static final int TOUCH_EXPLORATION_TAP_SLOP = 80;
+
+    /**
      * The maximum size of View's drawing cache, expressed in bytes. This size
      * should be at least equal to the size of the screen in ARGB888 format.
      */
@@ -185,6 +191,7 @@ public class ViewConfiguration {
     private final int mTouchSlop;
     private final int mPagingTouchSlop;
     private final int mDoubleTapSlop;
+    private final int mScaledTouchExplorationTapSlop;
     private final int mWindowTouchSlop;
     private final int mMaximumDrawingCacheSize;
     private final int mOverscrollDistance;
@@ -206,6 +213,7 @@ public class ViewConfiguration {
         mTouchSlop = TOUCH_SLOP;
         mPagingTouchSlop = PAGING_TOUCH_SLOP;
         mDoubleTapSlop = DOUBLE_TAP_SLOP;
+        mScaledTouchExplorationTapSlop = TOUCH_EXPLORATION_TAP_SLOP;
         mWindowTouchSlop = WINDOW_TOUCH_SLOP;
         //noinspection deprecation
         mMaximumDrawingCacheSize = MAXIMUM_DRAWING_CACHE_SIZE;
@@ -242,6 +250,7 @@ public class ViewConfiguration {
         mTouchSlop = (int) (sizeAndDensity * TOUCH_SLOP + 0.5f);
         mPagingTouchSlop = (int) (sizeAndDensity * PAGING_TOUCH_SLOP + 0.5f);
         mDoubleTapSlop = (int) (sizeAndDensity * DOUBLE_TAP_SLOP + 0.5f);
+        mScaledTouchExplorationTapSlop = (int) (density * TOUCH_EXPLORATION_TAP_SLOP + 0.5f);
         mWindowTouchSlop = (int) (sizeAndDensity * WINDOW_TOUCH_SLOP + 0.5f);
 
         // Size of the screen in bytes, in ARGB_8888 format
@@ -444,6 +453,17 @@ public class ViewConfiguration {
     }
 
     /**
+     * @return Distance between a touch up event denoting the end of a touch exploration
+     * gesture and the touch up event of a subsequent tap for the latter tap to be
+     * considered as a tap i.e. to perform a click.
+     *
+     * @hide
+     */
+    public int getScaledTouchExplorationTapSlop() {
+        return mScaledTouchExplorationTapSlop;
+    }
+
+    /**
      * @return Distance a touch must be outside the bounds of a window for it
      * to be counted as outside the window for purposes of dismissing that
      * window.