Reducing the click delay while screen magnification is enabled.

1. If screen magnification is enabled the user has to triple tap
   and lift or triple tap and hold to engage magnification. Hence,
   we delay the touch events until we are sure that it is no longer
   possible for the user to perform a multi-tap to engage
   magnification. While such a delay is unavoidable it feels a
   bit longer than it should be. This change reduces the delay
   between taps to be considered a multi-tap, essentially making
   the click delay shorter.

bug:7139918

Change-Id: I2100945171fff99600766193f0effdaef1f1db8f

Author: sganov

services/java/com/android/server/accessibility/ScreenMagnifier.java

@@ -128,6 +128,8 @@ public final class ScreenMagnifier implements EventStreamTransformation {
     private static final int DEFAULT_SCREEN_MAGNIFICATION_AUTO_UPDATE = 1;
     private static final float DEFAULT_WINDOW_ANIMATION_SCALE = 1.0f;
 
+    private static final int MULTI_TAP_TIME_SLOP_ADJUSTMENT = 50;
+
     private final IWindowManager mWindowManagerService = IWindowManager.Stub.asInterface(
             ServiceManager.getService("window"));
     private final WindowManager mWindowManager;
@@ -145,7 +147,8 @@ public final class ScreenMagnifier implements EventStreamTransformation {
     private final Viewport mViewport;
 
     private final int mTapTimeSlop = ViewConfiguration.getTapTimeout();
-    private final int mMultiTapTimeSlop = ViewConfiguration.getDoubleTapTimeout();
+    private final int mMultiTapTimeSlop =
+            ViewConfiguration.getDoubleTapTimeout() - MULTI_TAP_TIME_SLOP_ADJUSTMENT;
     private final int mTapDistanceSlop;
     private final int mMultiTapDistanceSlop;
 
@@ -617,7 +620,7 @@ public void onMotionEvent(MotionEvent event, int policyFlags) {
                     } else if (mTapCount < ACTION_TAP_COUNT) {
                         Message message = mHandler.obtainMessage(
                                 MESSAGE_TRANSITION_TO_DELEGATING_STATE);
-                        mHandler.sendMessageDelayed(message, mTapTimeSlop + mMultiTapDistanceSlop);
+                        mHandler.sendMessageDelayed(message, mMultiTapTimeSlop);
                     }
                     clearLastDownEvent();
                     mLastDownEvent = MotionEvent.obtain(event);