Say hello to Qt Android Sensors based on NDK API

Until Qt 5.9, we had to use JNI way because the NDK sensors API was
introduced in API-16. Starting with Qt 5.9 we can safely use the NDK API
as API_16 is the minimum API supported by Qt.
Using the NDK API instead of JNI boost the performance a lot! The CPU
usage dropped 2 to 4 times, from over 60% using the JNI to less than
20%.

[ChangeLog][Android] Rewrite Qt Android Sensors using NDK
API.

Change-Id: If3e3f1e56973e2a189662912b2a6ebfbd71dee14
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 167 insertions, 0 deletions

diff --git a/src/plugins/sensors/android/androidcompass.cpp b/src/plugins/sensors/android/androidcompass.cpp
new file mode 100644
index 00000000..653c5e99
--- /dev/null
+++ b/src/plugins/sensors/android/androidcompass.cpp
@@ -0,0 +1,167 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 BogDan Vatra <bogdan@kde.org>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtSensors module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*
+ * 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 "androidcompass.h"
+
+#include <qmath.h>
+
+#include "sensormanager.h"
+
+AndroidCompass::AndroidCompass(QSensor *sensor, QObject *parent)
+    : ThreadSafeSensorBackend(sensor, parent)
+{
+    setDescription("Compass");
+    setReading<QCompassReading>(&m_reading);
+    memset(&m_accelerometerEvent, 0, sizeof(ASensorVector));
+    memset(&m_magneticEvent, 0, sizeof(ASensorVector));
+    m_sensorEventQueue = ASensorManager_createEventQueue(m_sensorManager->manager(), m_sensorManager->looper(), -1, &looperCallback, this);
+    m_accelerometer = ASensorManager_getDefaultSensor(m_sensorManager->manager(), ASENSOR_TYPE_ACCELEROMETER);
+    m_magnetometer = ASensorManager_getDefaultSensor(m_sensorManager->manager(), ASENSOR_TYPE_MAGNETIC_FIELD);
+}
+
+AndroidCompass::~AndroidCompass()
+{
+    stop();
+    ASensorManager_destroyEventQueue(m_sensorManager->manager(), m_sensorEventQueue);
+}
+
+void AndroidCompass::start()
+{
+    ASensorEventQueue_enableSensor(m_sensorEventQueue, m_accelerometer);
+    if (sensor()->dataRate() > 0)
+        ASensorEventQueue_setEventRate(m_sensorEventQueue, m_accelerometer, std::max(ASensor_getMinDelay(m_accelerometer), sensor()->dataRate()));
+
+    ASensorEventQueue_enableSensor(m_sensorEventQueue, m_magnetometer);
+    if (sensor()->dataRate() > 0)
+        ASensorEventQueue_setEventRate(m_sensorEventQueue, m_magnetometer, std::max(ASensor_getMinDelay(m_magnetometer), sensor()->dataRate()));
+}
+
+void AndroidCompass::stop()
+{
+    ASensorEventQueue_disableSensor(m_sensorEventQueue, m_accelerometer);
+    ASensorEventQueue_disableSensor(m_sensorEventQueue, m_magnetometer);
+}
+
+void AndroidCompass::readAllEvents()
+{
+    {
+        ASensorEvent sensorEvent;
+        QMutexLocker lock(&m_sensorsMutex);
+        while (ASensorEventQueue_getEvents(m_sensorEventQueue, &sensorEvent, 1)) {
+            switch (sensorEvent.type) {
+            case ASENSOR_TYPE_ACCELEROMETER:
+                m_accelerometerEvent = sensorEvent.acceleration;
+                m_accelerometerEvent.status = m_accelerometerEvent.status == ASENSOR_STATUS_NO_CONTACT ? 0 : m_accelerometerEvent.status;
+                break;
+            case ASENSOR_TYPE_MAGNETIC_FIELD:
+                m_magneticEvent = sensorEvent.magnetic;
+                m_magneticEvent.status = m_magneticEvent.status == ASENSOR_STATUS_NO_CONTACT ? 0 : m_magneticEvent.status;
+                break;
+            }
+        }
+    }
+
+    QCoreApplication::postEvent(this, new FunctionEvent{[=]() {
+        // merged getRotationMatrix https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/hardware/SensorManager.java#1182
+        // and getOrientation https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/hardware/SensorManager.java#1477
+        QMutexLocker lock(&m_sensorsMutex);
+        auto Ax = qreal(m_accelerometerEvent.x);
+        auto Ay = qreal(m_accelerometerEvent.y);
+        auto Az = qreal(m_accelerometerEvent.z);
+
+        const qreal normsqA = (Ax * Ax + Ay * Ay + Az * Az);
+        const auto g = qreal(ASENSOR_STANDARD_GRAVITY);
+        const qreal freeFallGravitySquared = 0.01 * g * g;
+        if (normsqA < freeFallGravitySquared)
+            return;
+
+        auto Ex = qreal(m_magneticEvent.x);
+        auto Ey = qreal(m_magneticEvent.y);
+        auto Ez = qreal(m_magneticEvent.z);
+        qreal Hx = Ey * Az - Ez * Ay;
+        qreal Hy = Ez * Ax - Ex * Az;
+        qreal Hz = Ex * Ay - Ey * Ax;
+        const qreal normH = std::sqrt(Hx * Hx + Hy * Hy + Hz * Hz);
+
+        if (normH < 0.1)
+            return;
+        const qreal invH = 1.0 / normH;
+        Hx *= invH;
+        Hy *= invH;
+        Hz *= invH;
+        const qreal invA = 1.0 / std::sqrt(Ax * Ax + Ay * Ay + Az * Az);
+        Ax *= invA;
+        Ay *= invA;
+        Az *= invA;
+        const qreal My = Az * Hx - Ax * Hz;
+        qreal azimuth = std::atan2(Hy, My);
+        qreal accuracyValue = (m_accelerometerEvent.status + m_magneticEvent.status) / 6.0;
+        if (sensor()->skipDuplicates() && qFuzzyCompare(azimuth, m_reading.azimuth()) &&
+                qFuzzyCompare(accuracyValue, m_reading.calibrationLevel())) {
+            return;
+        }
+        m_reading.setAzimuth(qRadiansToDegrees(azimuth));
+        m_reading.setCalibrationLevel(accuracyValue);
+        newReadingAvailable();
+    }});
+}
+
+int AndroidCompass::looperCallback(int, int, void *data)
+{
+    auto self = reinterpret_cast<AndroidCompass*>(data);
+    self->readAllEvents();
+    return 1; // 1 means keep receiving events
+}