The Tor Browser: widget/gonk/ProcessOrientation.cpp@b8a032363ba2 (annotated)

widget/gonk/ProcessOrientation.cpp@b8a032363ba2 (annotated)

widget/gonk/ProcessOrientation.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * Copyright (c) 2013, Linux Foundation. All rights reserved
  *
  * Copyright (C) 2008 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.
  */
 #include "base/basictypes.h"
 #include "mozilla/Hal.h"
 #include "nsIScreen.h"
 #include "nsIScreenManager.h"
 #include "OrientationObserver.h"
 #include "ProcessOrientation.h"
 #include "mozilla/HalSensor.h"
 #include "math.h"
 #include "limits.h"
 #include "android/log.h"
 #if 0
 #define LOGD(args...)  __android_log_print(ANDROID_LOG_DEBUG, "ProcessOrientation" , ## args)
 #else
 #define LOGD(args...)
 #endif
 namespace mozilla {
 // We work with all angles in degrees in this class.
 #define RADIANS_TO_DEGREES (180/M_PI)
 // Number of nanoseconds per millisecond.
 #define NANOS_PER_MS 1000000
 // Indices into SensorEvent.values for the accelerometer sensor.
 #define ACCELEROMETER_DATA_X 0
 #define ACCELEROMETER_DATA_Y 1
 #define ACCELEROMETER_DATA_Z 2
 // The minimum amount of time that a predicted rotation must be stable before
 // it is accepted as a valid rotation proposal. This value can be quite small
 // because the low-pass filter already suppresses most of the noise so we're
 // really just looking for quick confirmation that the last few samples are in
 // agreement as to the desired orientation.
 #define PROPOSAL_SETTLE_TIME_NANOS (40*NANOS_PER_MS)
 // The minimum amount of time that must have elapsed since the device last
 // exited the flat state (time since it was picked up) before the proposed
 // rotation can change.
 #define PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS (500*NANOS_PER_MS)
 // The minimum amount of time that must have elapsed since the device stopped
 // swinging (time since device appeared to be in the process of being put down
 // or put away into a pocket) before the proposed rotation can change.
 #define PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS (300*NANOS_PER_MS)
 // The minimum amount of time that must have elapsed since the device stopped
 // undergoing external acceleration before the proposed rotation can change.
 #define PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS (500*NANOS_PER_MS)
 // If the tilt angle remains greater than the specified angle for a minimum of
 // the specified time, then the device is deemed to be lying flat
 // (just chillin' on a table).
 #define FLAT_ANGLE 75
 #define FLAT_TIME_NANOS (1000*NANOS_PER_MS)
 // If the tilt angle has increased by at least delta degrees within the
 // specified amount of time, then the device is deemed to be swinging away
 // from the user down towards flat (tilt = 90).
 #define SWING_AWAY_ANGLE_DELTA 20
 #define SWING_TIME_NANOS (300*NANOS_PER_MS)
 // The maximum sample inter-arrival time in milliseconds. If the acceleration
 // samples are further apart than this amount in time, we reset the state of
 // the low-pass filter and orientation properties.  This helps to handle
 // boundary conditions when the device is turned on, wakes from suspend or
 // there is a significant gap in samples.
 #define MAX_FILTER_DELTA_TIME_NANOS (1000*NANOS_PER_MS)
 // The acceleration filter time constant.
 //
 // This time constant is used to tune the acceleration filter such that
 // impulses and vibrational noise (think car dock) is suppressed before we try
 // to calculate the tilt and orientation angles.
 //
 // The filter time constant is related to the filter cutoff frequency, which
 // is the frequency at which signals are attenuated by 3dB (half the passband
 // power). Each successive octave beyond this frequency is attenuated by an
 // additional 6dB.
 //
 // Given a time constant t in seconds, the filter cutoff frequency Fc in Hertz
 // is given by Fc = 1 / (2pi * t).
 //
 // The higher the time constant, the lower the cutoff frequency, so more noise
 // will be suppressed.
 //
 // Filtering adds latency proportional the time constant (inversely
 // proportional to the cutoff frequency) so we don't want to make the time
 // constant too large or we can lose responsiveness.  Likewise we don't want
 // to make it too small or we do a poor job suppressing acceleration spikes.
 // Empirically, 100ms seems to be too small and 500ms is too large. Android
 // default is 200.
 #define FILTER_TIME_CONSTANT_MS 200.0f
 // State for orientation detection. Thresholds for minimum and maximum
 // allowable deviation from gravity.
 //
 // If the device is undergoing external acceleration (being bumped, in a car
 // that is turning around a corner or a plane taking off) then the magnitude
 // may be substantially more or less than gravity.  This can skew our
 // orientation detection by making us think that up is pointed in a different
 // direction.
 //
 // Conversely, if the device is in freefall, then there will be no gravity to
 // measure at all.  This is problematic because we cannot detect the orientation
 // without gravity to tell us which way is up. A magnitude near 0 produces
 // singularities in the tilt and orientation calculations.
 //
 // In both cases, we postpone choosing an orientation.
 //
 // However, we need to tolerate some acceleration because the angular momentum
 // of turning the device can skew the observed acceleration for a short period
 // of time.
 #define NEAR_ZERO_MAGNITUDE 1 // m/s^2
 #define ACCELERATION_TOLERANCE 4 // m/s^2
 #define STANDARD_GRAVITY 9.80665f
 #define MIN_ACCELERATION_MAGNITUDE (STANDARD_GRAVITY-ACCELERATION_TOLERANCE)
 #define MAX_ACCELERATION_MAGNITUDE (STANDARD_GRAVITY+ACCELERATION_TOLERANCE)
 // Maximum absolute tilt angle at which to consider orientation data. Beyond
 // this (i.e. when screen is facing the sky or ground), we completely ignore
 // orientation data.
 #define MAX_TILT 75
 // 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 angle is within the gap between the current orientation and the
 // adjacent orientation.
 #define ADJACENT_ORIENTATION_ANGLE_GAP 45
 const int
 ProcessOrientation::tiltTolerance[][4] = {
   {-25, 70}, // ROTATION_0
   {-25, 65}, // ROTATION_90
   {-25, 60}, // ROTATION_180
   {-25, 65}  // ROTATION_270
 };
 int
 ProcessOrientation::GetProposedRotation()
 {
   return mProposedRotation;
 }
 int
 ProcessOrientation::OnSensorChanged(const SensorData& event,
                                     int deviceCurrentRotation)
 {
   // The vector given in the SensorEvent points straight up (towards the sky)
   // under ideal conditions (the phone is not accelerating). I'll call this up
   // vector elsewhere.
   const InfallibleTArray<float>& values = event.values();
   float x = values[ACCELEROMETER_DATA_X];
   float y = values[ACCELEROMETER_DATA_Y];
   float z = values[ACCELEROMETER_DATA_Z];
   LOGD
     ("ProcessOrientation: Raw acceleration vector: x = %f, y = %f, z = %f,"
      "magnitude = %f\n", x, y, z, sqrt(x * x + y * y + z * z));
   // Apply a low-pass filter to the acceleration up vector in cartesian space.
   // Reset the orientation listener state if the samples are too far apart in
   // time or when we see values of (0, 0, 0) which indicates that we polled the
   // accelerometer too soon after turning it on and we don't have any data yet.
   const long now = event.timestamp();
   const long then = mLastFilteredTimestampNanos;
   const float timeDeltaMS = (now - then) * 0.000001f;
   bool skipSample = false;
   if (now < then
       || now > then + MAX_FILTER_DELTA_TIME_NANOS
       || (x == 0 && y == 0 && z == 0)) {
     LOGD
       ("ProcessOrientation: Resetting orientation listener.");
     Reset();
     skipSample = true;
   } else {
     const float alpha = timeDeltaMS / (FILTER_TIME_CONSTANT_MS + timeDeltaMS);
     x = alpha * (x - mLastFilteredX) + mLastFilteredX;
     y = alpha * (y - mLastFilteredY) + mLastFilteredY;
     z = alpha * (z - mLastFilteredZ) + mLastFilteredZ;
     LOGD
       ("ProcessOrientation: Filtered acceleration vector: x=%f, y=%f, z=%f,"
        "magnitude=%f", z, y, z, sqrt(x * x + y * y + z * z));
     skipSample = false;
   }
   mLastFilteredTimestampNanos = now;
   mLastFilteredX = x;
   mLastFilteredY = y;
   mLastFilteredZ = z;
   bool isAccelerating = false;
   bool isFlat = false;
   bool isSwinging = false;
   if (skipSample) {
     return -1;
   }
   // Calculate the magnitude of the acceleration vector.
   const float magnitude = sqrt(x * x + y * y + z * z);
   if (magnitude < NEAR_ZERO_MAGNITUDE) {
     LOGD
       ("ProcessOrientation: Ignoring sensor data, magnitude too close to"
        " zero.");
     ClearPredictedRotation();
   } else {
     // Determine whether the device appears to be undergoing external
     // acceleration.
     if (this->IsAccelerating(magnitude)) {
       isAccelerating = true;
       mAccelerationTimestampNanos = now;
     }
     // Calculate the tilt angle. This is the angle between the up vector and
     // the x-y plane (the plane of the screen) in a range of [-90, 90]
     // degrees.
     //   -90 degrees: screen horizontal and facing the ground (overhead)
     //     0 degrees: screen vertical
     //    90 degrees: screen horizontal and facing the sky (on table)
     const int tiltAngle =
       static_cast<int>(roundf(asin(z / magnitude) * RADIANS_TO_DEGREES));
     AddTiltHistoryEntry(now, tiltAngle);
     // Determine whether the device appears to be flat or swinging.
     if (this->IsFlat(now)) {
       isFlat = true;
       mFlatTimestampNanos = now;
     }
     if (this->IsSwinging(now, tiltAngle)) {
       isSwinging = true;
       mSwingTimestampNanos = now;
     }
     // If the tilt angle is too close to horizontal then we cannot determine
     // the orientation angle of the screen.
     if (abs(tiltAngle) > MAX_TILT) {
       LOGD
         ("ProcessOrientation: Ignoring sensor data, tilt angle too high:"
          " tiltAngle=%d", tiltAngle);
       ClearPredictedRotation();
     } else {
       // Calculate the orientation angle.
       // This is the angle between the x-y projection of the up vector onto
       // the +y-axis, increasing clockwise in a range of [0, 360] degrees.
       int orientationAngle =
         static_cast<int>(roundf(-atan2f(-x, y) * RADIANS_TO_DEGREES));
       if (orientationAngle < 0) {
         // atan2 returns [-180, 180]; normalize to [0, 360]
         orientationAngle += 360;
       }
       // Find the nearest rotation.
       int nearestRotation = (orientationAngle + 45) / 90;
       if (nearestRotation == 4) {
         nearestRotation = 0;
       }
       // Determine the predicted orientation.
       if (IsTiltAngleAcceptable(nearestRotation, tiltAngle)
           &&
           IsOrientationAngleAcceptable
           (nearestRotation, orientationAngle, deviceCurrentRotation)) {
         UpdatePredictedRotation(now, nearestRotation);
         LOGD
           ("ProcessOrientation: Predicted: tiltAngle=%d, orientationAngle=%d,"
            " predictedRotation=%d, predictedRotationAgeMS=%f",
            tiltAngle,
            orientationAngle,
            mPredictedRotation,
            ((now - mPredictedRotationTimestampNanos) * 0.000001f));
       } else {
         LOGD
           ("ProcessOrientation: Ignoring sensor data, no predicted rotation:"
            " tiltAngle=%d, orientationAngle=%d",
            tiltAngle,
            orientationAngle);
         ClearPredictedRotation();
       }
     }
   }
   // Determine new proposed rotation.
   const int oldProposedRotation = mProposedRotation;
   if (mPredictedRotation < 0 || IsPredictedRotationAcceptable(now)) {
     mProposedRotation = mPredictedRotation;
   }
   // Write final statistics about where we are in the orientation detection
   // process.
   LOGD
     ("ProcessOrientation: Result: oldProposedRotation=%d,currentRotation=%d, "
      "proposedRotation=%d, predictedRotation=%d, timeDeltaMS=%f, "
      "isAccelerating=%d, isFlat=%d, isSwinging=%d, timeUntilSettledMS=%f, "
      "timeUntilAccelerationDelayExpiredMS=%f, timeUntilFlatDelayExpiredMS=%f, "
      "timeUntilSwingDelayExpiredMS=%f",
      oldProposedRotation,
      deviceCurrentRotation, mProposedRotation,
      mPredictedRotation, timeDeltaMS, isAccelerating, isFlat,
      isSwinging, RemainingMS(now,
                              mPredictedRotationTimestampNanos +
                              PROPOSAL_SETTLE_TIME_NANOS),
      RemainingMS(now,
                  mAccelerationTimestampNanos +
                  PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS),
      RemainingMS(now,
                  mFlatTimestampNanos +
                  PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS),
      RemainingMS(now,
                  mSwingTimestampNanos +
                  PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS));
   // Tell the listener.
   if (mProposedRotation != oldProposedRotation && mProposedRotation >= 0) {
     LOGD
       ("ProcessOrientation: Proposed rotation changed!  proposedRotation=%d, "
        "oldProposedRotation=%d",
        mProposedRotation,
        oldProposedRotation);
     return mProposedRotation;
   }
   // Don't rotate screen
   return -1;
 }
 bool
 ProcessOrientation::IsTiltAngleAcceptable(int rotation, int tiltAngle)
 {
   return (tiltAngle >= tiltTolerance[rotation][0]
           && tiltAngle <= tiltTolerance[rotation][1]);
 }
 bool
 ProcessOrientation::IsOrientationAngleAcceptable(int rotation,
                                                  int orientationAngle,
                                                  int currentRotation)
 {
   // If there is no current rotation, then there is no gap.
   // The gap is used only to introduce hysteresis among advertised orientation
   // changes to avoid flapping.
   if (currentRotation < 0) {
     return true;
   }
   // If the specified rotation is the same or is counter-clockwise adjacent
   // to the current rotation, then we set a lower bound on the orientation
   // angle. For example, if currentRotation is ROTATION_0 and proposed is
   // ROTATION_90, then we want to check orientationAngle > 45 + GAP / 2.
   if (rotation == currentRotation || rotation == (currentRotation + 1) % 4) {
     int lowerBound = rotation * 90 - 45 + ADJACENT_ORIENTATION_ANGLE_GAP / 2;
     if (rotation == 0) {
       if (orientationAngle >= 315 && orientationAngle < lowerBound + 360) {
         return false;
       }
     } else {
       if (orientationAngle < lowerBound) {
         return false;
       }
     }
   }
   // If the specified rotation is the same or is clockwise adjacent, then we
   // set an upper bound on the orientation angle. For example, if
   // currentRotation is ROTATION_0 and rotation is ROTATION_270, then we want
   // to check orientationAngle < 315 - GAP / 2.
   if (rotation == currentRotation || rotation == (currentRotation + 3) % 4) {
     int upperBound = rotation * 90 + 45 - ADJACENT_ORIENTATION_ANGLE_GAP / 2;
     if (rotation == 0) {
       if (orientationAngle <= 45 && orientationAngle > upperBound) {
         return false;
       }
     } else {
       if (orientationAngle > upperBound) {
         return false;
       }
     }
   }
   return true;
 }
 bool
 ProcessOrientation::IsPredictedRotationAcceptable(long now)
 {
   // The predicted rotation must have settled long enough.
   if (now < mPredictedRotationTimestampNanos + PROPOSAL_SETTLE_TIME_NANOS) {
     return false;
   }
   // The last flat state (time since picked up) must have been sufficiently long
   // ago.
   if (now < mFlatTimestampNanos + PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS) {
     return false;
   }
   // The last swing state (time since last movement to put down) must have been
   // sufficiently long ago.
   if (now < mSwingTimestampNanos + PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS) {
     return false;
   }
   // The last acceleration state must have been sufficiently long ago.
   if (now < mAccelerationTimestampNanos
       + PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS) {
     return false;
   }
   // Looks good!
   return true;
 }
 int
 ProcessOrientation::Reset()
 {
   mLastFilteredTimestampNanos = LONG_MIN;
   mProposedRotation = -1;
   mFlatTimestampNanos = LONG_MIN;
   mSwingTimestampNanos = LONG_MIN;
   mAccelerationTimestampNanos = LONG_MIN;
   ClearPredictedRotation();
   ClearTiltHistory();
   return -1;
 }
 void
 ProcessOrientation::ClearPredictedRotation()
 {
   mPredictedRotation = -1;
   mPredictedRotationTimestampNanos = LONG_MIN;
 }
 void
 ProcessOrientation::UpdatePredictedRotation(long now, int rotation)
 {
   if (mPredictedRotation != rotation) {
     mPredictedRotation = rotation;
     mPredictedRotationTimestampNanos = now;
   }
 }
 bool
 ProcessOrientation::IsAccelerating(float magnitude)
 {
   return magnitude < MIN_ACCELERATION_MAGNITUDE
     || magnitude > MAX_ACCELERATION_MAGNITUDE;
 }
 void
 ProcessOrientation::ClearTiltHistory()
 {
   mTiltHistory.history[0].timestampNanos = LONG_MIN;
   mTiltHistory.index = 1;
 }
 void
 ProcessOrientation::AddTiltHistoryEntry(long now, float tilt)
 {
   mTiltHistory.history[mTiltHistory.index].tiltAngle = tilt;
   mTiltHistory.history[mTiltHistory.index].timestampNanos = now;
   mTiltHistory.index = (mTiltHistory.index + 1) % TILT_HISTORY_SIZE;
   mTiltHistory.history[mTiltHistory.index].timestampNanos = LONG_MIN;
 }
 bool
 ProcessOrientation::IsFlat(long now)
 {
   for (int i = mTiltHistory.index; (i = NextTiltHistoryIndex(i)) >= 0;) {
     if (mTiltHistory.history[i].tiltAngle < FLAT_ANGLE) {
       break;
     }
     if (mTiltHistory.history[i].timestampNanos + FLAT_TIME_NANOS <= now) {
       // Tilt has remained greater than FLAT_TILT_ANGLE for FLAT_TIME_NANOS.
       return true;
     }
   }
   return false;
 }
 bool
 ProcessOrientation::IsSwinging(long now, float tilt)
 {
   for (int i = mTiltHistory.index; (i = NextTiltHistoryIndex(i)) >= 0;) {
     if (mTiltHistory.history[i].timestampNanos + SWING_TIME_NANOS < now) {
       break;
     }
     if (mTiltHistory.history[i].tiltAngle + SWING_AWAY_ANGLE_DELTA <= tilt) {
       // Tilted away by SWING_AWAY_ANGLE_DELTA within SWING_TIME_NANOS.
       return true;
     }
   }
   return false;
 }
 int
 ProcessOrientation::NextTiltHistoryIndex(int index)
 {
   index = (index == 0 ? TILT_HISTORY_SIZE : index) - 1;
   return mTiltHistory.history[index].timestampNanos != LONG_MIN ? index : -1;
 }
 float
 ProcessOrientation::RemainingMS(long now, long until)
 {
   return now >= until ? 0 : (until - now) * 0.000001f;
 }
 } // namespace mozilla

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widget/gonk/ProcessOrientation.cpp@b8a032363ba2 (annotated)

widget/gonk/ProcessOrientation.cpp