Improve window orientation listener.

Take into account whether the device appeared to be overhead facing
down.  If so, suppress orientation changes until the device is tilted
back upright again.  This should improve behavior in situations such
as reading in bed and rolling over to one side.

Change-Id: I683515e1867626dacc71d90eaacb32e75ab41827
diff --git a/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java b/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
index 2c51abb..d909568 100644
--- a/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
+++ b/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
@@ -5541,8 +5541,13 @@
         pw.print(prefix); pw.print("mDemoHdmiRotation="); pw.print(mDemoHdmiRotation);
                 pw.print(" mDemoHdmiRotationLock="); pw.println(mDemoHdmiRotationLock);
         pw.print(prefix); pw.print("mUndockedHdmiRotation="); pw.println(mUndockedHdmiRotation);
+
         mStatusBarController.dump(pw, prefix);
         mNavigationBarController.dump(pw, prefix);
         PolicyControl.dump(prefix, pw);
+
+        if (mOrientationListener != null) {
+            mOrientationListener.dump(pw, prefix);
+        }
     }
 }
diff --git a/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java b/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java
index 0c77556..2cc33b5f 100644
--- a/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java
+++ b/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java
@@ -26,6 +26,9 @@
 import android.util.FloatMath;
 import android.util.Log;
 import android.util.Slog;
+import android.util.TimeUtils;
+
+import java.io.PrintWriter;
 
 /**
  * A special helper class used by the WindowManager
@@ -181,6 +184,19 @@
      */
     public abstract void onProposedRotationChanged(int rotation);
 
+    public void dump(PrintWriter pw, String prefix) {
+        synchronized (mLock) {
+            pw.println(prefix + TAG);
+            prefix += "  ";
+            pw.println(prefix + "mEnabled=" + mEnabled);
+            pw.println(prefix + "mCurrentRotation=" + mCurrentRotation);
+            pw.println(prefix + "mSensor=" + mSensor);
+            pw.println(prefix + "mRate=" + mRate);
+
+            mSensorEventListener.dumpLocked(pw, prefix);
+        }
+    }
+
     /**
      * This class filters the raw accelerometer data and tries to detect actual changes in
      * orientation. This is a very ill-defined problem so there are a lot of tweakable parameters,
@@ -342,6 +358,14 @@
             /* ROTATION_270 */ { -25, 65 }
         };
 
+        // The tilt angle below which we conclude that the user is holding the device
+        // overhead reading in bed and lock into that state.
+        private final int TILT_OVERHEAD_ENTER = -40;
+
+        // The tilt angle above which we conclude that the user would like a rotation
+        // change to occur and unlock from the overhead state.
+        private final int TILT_OVERHEAD_EXIT = -15;
+
         // The gap angle in degrees between adjacent orientation angles for hysteresis.
         // This creates a "dead zone" between the current orientation and a proposed
         // adjacent orientation.  No orientation proposal is made when the orientation
@@ -364,12 +388,18 @@
 
         // Timestamp when the device last appeared to be flat for sure (the flat delay elapsed).
         private long mFlatTimestampNanos;
+        private boolean mFlat;
 
         // Timestamp when the device last appeared to be swinging.
         private long mSwingTimestampNanos;
+        private boolean mSwinging;
 
         // Timestamp when the device last appeared to be undergoing external acceleration.
         private long mAccelerationTimestampNanos;
+        private boolean mAccelerating;
+
+        // Whether we are locked into an overhead usage mode.
+        private boolean mOverhead;
 
         // History of observed tilt angles.
         private static final int TILT_HISTORY_SIZE = 40;
@@ -381,6 +411,19 @@
             return mProposedRotation;
         }
 
+        public void dumpLocked(PrintWriter pw, String prefix) {
+            pw.println(prefix + "mProposedRotation=" + mProposedRotation);
+            pw.println(prefix + "mPredictedRotation=" + mPredictedRotation);
+            pw.println(prefix + "mLastFilteredX=" + mLastFilteredX);
+            pw.println(prefix + "mLastFilteredY=" + mLastFilteredY);
+            pw.println(prefix + "mLastFilteredZ=" + mLastFilteredZ);
+            pw.println(prefix + "mTiltHistory={last: " + getLastTiltLocked() + "}");
+            pw.println(prefix + "mFlat=" + mFlat);
+            pw.println(prefix + "mSwinging=" + mSwinging);
+            pw.println(prefix + "mAccelerating=" + mAccelerating);
+            pw.println(prefix + "mOverhead=" + mOverhead);
+        }
+
         @Override
         public void onAccuracyChanged(Sensor sensor, int accuracy) {
         }
@@ -478,7 +521,18 @@
 
                         // If the tilt angle is too close to horizontal then we cannot determine
                         // the orientation angle of the screen.
-                        if (Math.abs(tiltAngle) > MAX_TILT) {
+                        if (tiltAngle <= TILT_OVERHEAD_ENTER) {
+                            mOverhead = true;
+                        } else if (tiltAngle >= TILT_OVERHEAD_EXIT) {
+                            mOverhead = false;
+                        }
+                        if (mOverhead) {
+                            if (LOG) {
+                                Slog.v(TAG, "Ignoring sensor data, device is overhead: "
+                                        + "tiltAngle=" + tiltAngle);
+                            }
+                            clearPredictedRotationLocked();
+                        } else if (Math.abs(tiltAngle) > MAX_TILT) {
                             if (LOG) {
                                 Slog.v(TAG, "Ignoring sensor data, tilt angle too high: "
                                         + "tiltAngle=" + tiltAngle);
@@ -526,6 +580,9 @@
                         }
                     }
                 }
+                mFlat = isFlat;
+                mSwinging = isSwinging;
+                mAccelerating = isAccelerating;
 
                 // Determine new proposed rotation.
                 oldProposedRotation = mProposedRotation;
@@ -543,6 +600,7 @@
                             + ", isAccelerating=" + isAccelerating
                             + ", isFlat=" + isFlat
                             + ", isSwinging=" + isSwinging
+                            + ", isOverhead=" + mOverhead
                             + ", timeUntilSettledMS=" + remainingMS(now,
                                     mPredictedRotationTimestampNanos + PROPOSAL_SETTLE_TIME_NANOS)
                             + ", timeUntilAccelerationDelayExpiredMS=" + remainingMS(now,
@@ -660,8 +718,12 @@
             mLastFilteredTimestampNanos = Long.MIN_VALUE;
             mProposedRotation = -1;
             mFlatTimestampNanos = Long.MIN_VALUE;
+            mFlat = false;
             mSwingTimestampNanos = Long.MIN_VALUE;
+            mSwinging = false;
             mAccelerationTimestampNanos = Long.MIN_VALUE;
+            mAccelerating = false;
+            mOverhead = false;
             clearPredictedRotationLocked();
             clearTiltHistoryLocked();
         }
@@ -726,6 +788,11 @@
             return mTiltHistoryTimestampNanos[index] != Long.MIN_VALUE ? index : -1;
         }
 
+        private float getLastTiltLocked() {
+            int index = nextTiltHistoryIndexLocked(mTiltHistoryIndex);
+            return index >= 0 ? mTiltHistory[index] : Float.NaN;
+        }
+
         private float remainingMS(long now, long until) {
             return now >= until ? 0 : (until - now) * 0.000001f;
         }