Add API for duplicate skipping

Duplicate skipping enables omitting reading values
that are very similar to the previous one, thus saving
processing power.

Implement this for the Blackberry backend.

Change-Id: Ic608d8ca795b5a2e0bca5a75a62e8005c283c620
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>

10 files changed, 105 insertions, 15 deletions

diff --git a/src/imports/sensors/plugins.qmltypes b/src/imports/sensors/plugins.qmltypes
index 1429ae79..fe9c961d 100644
--- a/src/imports/sensors/plugins.qmltypes
+++ b/src/imports/sensors/plugins.qmltypes
@@ -157,6 +157,7 @@ Module {
         name: "QmlSensor"
         prototype: "QObject"
         exports: ["Sensor 5.0", "Sensor 5.1"]
+        exportMetaObjectRevisions: [0, 1]
         Property { name: "identifier"; type: "string" }
         Property { name: "type"; type: "string"; isReadonly: true }
         Property { name: "connectedToBackend"; type: "bool"; isReadonly: true }
@@ -170,6 +171,11 @@ Module {
         Property { name: "description"; type: "string"; isReadonly: true }
         Property { name: "error"; type: "int"; isReadonly: true }
         Property { name: "alwaysOn"; type: "bool" }
+        Property { name: "skipDuplicates"; revision: 1; type: "bool" }
+        Signal {
+            name: "skipDuplicatesChanged"
+            Parameter { name: "skipDuplicates"; type: "bool" }
+        }
         Method { name: "start"; type: "bool" }
         Method { name: "stop" }
     }
diff --git a/src/imports/sensors/qmlsensor.cpp b/src/imports/sensors/qmlsensor.cpp
index ec1b0691..40a0ebfe 100644
--- a/src/imports/sensors/qmlsensor.cpp
+++ b/src/imports/sensors/qmlsensor.cpp
@@ -171,6 +171,25 @@ void QmlSensor::setAlwaysOn(bool alwaysOn)
 }
 
 /*!
+    \qmlproperty bool Sensor::skipDuplicates
+    \since QtSensors 5.1
+
+    This property indicates whether duplicate reading values should be omitted.
+
+    Please see QSensor::skipDuplicates for information about this property.
+*/
+
+bool QmlSensor::skipDuplicates() const
+{
+    return sensor()->skipDuplicates();
+}
+
+void QmlSensor::setSkipDuplicates(bool skipDuplicates)
+{
+    sensor()->setSkipDuplicates(skipDuplicates);
+}
+
+/*!
     \qmlproperty list<Range> Sensor::availableDataRates
     This property holds the data rates that the sensor supports.
 
@@ -323,6 +342,7 @@ void QmlSensor::componentComplete()
     connect(sensor(), SIGNAL(sensorError(int)), this, SIGNAL(errorChanged()));
     connect(sensor(), SIGNAL(activeChanged()), this, SIGNAL(activeChanged()));
     connect(sensor(), SIGNAL(alwaysOnChanged()), this, SIGNAL(alwaysOnChanged()));
+    connect(sensor(), SIGNAL(skipDuplicatesChanged(bool)), this, SIGNAL(skipDuplicatesChanged(bool)));
 
     // We need to set this on the sensor object now
     sensor()->setIdentifier(m_identifier.toLocal8Bit());
diff --git a/src/imports/sensors/qmlsensor.h b/src/imports/sensors/qmlsensor.h
index a4ac852d..e287f194 100644
--- a/src/imports/sensors/qmlsensor.h
+++ b/src/imports/sensors/qmlsensor.h
@@ -71,6 +71,7 @@ class QmlSensor : public QObject, public QQmlParserStatus
     Q_PROPERTY(QString description READ description NOTIFY descriptionChanged)
     Q_PROPERTY(int error READ error NOTIFY errorChanged)
     Q_PROPERTY(bool alwaysOn READ isAlwaysOn WRITE setAlwaysOn NOTIFY alwaysOnChanged)
+    Q_PROPERTY(bool skipDuplicates READ skipDuplicates WRITE setSkipDuplicates NOTIFY skipDuplicatesChanged REVISION 1)
 public:
     explicit QmlSensor(QObject *parent = 0);
     ~QmlSensor();
@@ -90,6 +91,9 @@ public:
     bool isAlwaysOn() const;
     void setAlwaysOn(bool alwaysOn);
 
+    bool skipDuplicates() const;
+    void setSkipDuplicates(bool skipDuplicates);
+
     QQmlListProperty<QmlSensorRange> availableDataRates() const;
     int dataRate() const;
     void setDataRate(int rate);
@@ -120,6 +124,7 @@ Q_SIGNALS:
     void descriptionChanged();
     void errorChanged();
     void alwaysOnChanged();
+    void skipDuplicatesChanged(bool skipDuplicates);
 
 protected:
     virtual QSensor *sensor() const = 0;
diff --git a/src/imports/sensors/sensors.cpp b/src/imports/sensors/sensors.cpp
index 9392baf3..3f774313 100644
--- a/src/imports/sensors/sensors.cpp
+++ b/src/imports/sensors/sensors.cpp
@@ -133,7 +133,7 @@ public:
         qmlRegisterSingletonType  <QmlSensorGlobal             >(package, major, minor, "QmlSensors", global_object_50);
         qmlRegisterUncreatableType<QmlSensorRange              >(package, major, minor, "Range",                QLatin1String("Cannot create Range"));
         qmlRegisterUncreatableType<QmlSensorOutputRange        >(package, major, minor, "OutputRange",          QLatin1String("Cannot create OutputRange"));
-        qmlRegisterUncreatableType<QmlSensor                   >(package, major, minor, "Sensor",               QLatin1String("Cannot create Sensor"));
+        qmlRegisterUncreatableType<QmlSensor,1                 >(package, major, minor, "Sensor",               QLatin1String("Cannot create Sensor"));
         qmlRegisterUncreatableType<QmlSensorReading            >(package, major, minor, "SensorReading",        QLatin1String("Cannot create SensorReading"));
         qmlRegisterType           <QmlAccelerometer,1          >(package, major, minor, "Accelerometer");
         qmlRegisterUncreatableType<QmlAccelerometerReading     >(package, major, minor, "AccelerometerReading", QLatin1String("Cannot create AccelerometerReading"));
diff --git a/src/plugins/sensors/blackberry/bborientationsensor.cpp b/src/plugins/sensors/blackberry/bborientationsensor.cpp
index 68ed735b..3d9d120c 100644
--- a/src/plugins/sensors/blackberry/bborientationsensor.cpp
+++ b/src/plugins/sensors/blackberry/bborientationsensor.cpp
@@ -44,6 +44,9 @@ BbOrientationSensor::BbOrientationSensor(QSensor *sensor)
     : BbSensorBackend<QOrientationReading>(devicePath(), SENSOR_TYPE_ORIENTATION, sensor)
 {
     setDescription(QLatin1String("Device orientation"));
+
+    // Orientation rarely changes, so enable skipping of duplicates by default
+    sensor->setSkipDuplicates(true);
 }
 
 QString BbOrientationSensor::devicePath()
@@ -51,19 +54,6 @@ QString BbOrientationSensor::devicePath()
     return QLatin1String("/dev/sensor/orientation");
 }
 
-void BbOrientationSensor::start()
-{
-    BbSensorBackend<QOrientationReading>::start();
-
-    // Orientation rarely changes, so enable skiping of duplicates
-    sensor_devctl_skipdupevent_u deviceSkip;
-    deviceSkip.tx.enable = 1;
-    const int result = devctl(deviceFile().handle(), DCMD_SENSOR_SKIPDUPEVENT, &deviceSkip,
-                              sizeof(deviceSkip), NULL);
-    if (result != EOK)
-        perror("Enabling duplicate skipping for orientation sensor failed");
-}
-
 void BbOrientationSensor::additionalDeviceInit()
 {
     // When querying the OS service for the range, it gives us the angles, which we don't need.
diff --git a/src/plugins/sensors/blackberry/bborientationsensor.h b/src/plugins/sensors/blackberry/bborientationsensor.h
index 07dc3d0f..85c7bd67 100644
--- a/src/plugins/sensors/blackberry/bborientationsensor.h
+++ b/src/plugins/sensors/blackberry/bborientationsensor.h
@@ -53,7 +53,6 @@ public:
 
     static QString devicePath();
 
-    void start() Q_DECL_OVERRIDE;
     void additionalDeviceInit() Q_DECL_OVERRIDE;
     bool addDefaultRange() Q_DECL_OVERRIDE;
 
diff --git a/src/plugins/sensors/blackberry/bbsensorbackend.cpp b/src/plugins/sensors/blackberry/bbsensorbackend.cpp
index 324929fd..9850d4dd 100644
--- a/src/plugins/sensors/blackberry/bbsensorbackend.cpp
+++ b/src/plugins/sensors/blackberry/bbsensorbackend.cpp
@@ -254,6 +254,16 @@ void BbSensorBackendBase::start()
         }
     }
 
+    // Enable/disable duplicate skipping
+    sensor_devctl_skipdupevent_u deviceSkip;
+    deviceSkip.tx.enable = sensor()->skipDuplicates();
+    const int result = devctl(deviceFile().handle(), DCMD_SENSOR_SKIPDUPEVENT, &deviceSkip,
+                              sizeof(deviceSkip), NULL);
+    if (result != EOK) {
+        perror(QString::fromLatin1("Setting duplicate skipping for %1 failed")
+               .arg(m_deviceFile.fileName()).toLocal8Bit());
+    }
+
     // Explicitly switch to non-blocking mode, otherwise read() will wait until new sensor
     // data is available, and we have no way to check if there is more data or not (bytesAvailable()
     // does not work for unbuffered mode)
@@ -299,6 +309,7 @@ bool BbSensorBackendBase::isFeatureSupported(QSensor::Feature feature) const
     case QSensor::AlwaysOn:
     case QSensor::Buffering:
     case QSensor::AccelerationMode:
+    case QSensor::SkipDuplicates:
         return true;
     case QSensor::Reserved:
     case QSensor::GeoValues:
diff --git a/src/sensors/qsensor.cpp b/src/sensors/qsensor.cpp
index 4c3715c2..f93ef883 100644
--- a/src/sensors/qsensor.cpp
+++ b/src/sensors/qsensor.cpp
@@ -189,6 +189,9 @@ void QSensorPrivate::init(const QByteArray &sensorType)
                      QSensor::bufferSize property.
     \value AlwaysOn The backend supports changing the policy on whether to suspend when idle,
                     controlled by the QSensor::alwaysOn property.
+    \value SkipDuplicates The backend supports skipping of same or very similar successive
+                          readings. This can be enabled by setting the QSensor::skipDuplicates
+                          property to true.
 
     The features of QMagnetometer are:
 
@@ -434,6 +437,54 @@ bool QSensor::isAlwaysOn() const
 }
 
 /*!
+    \property QSensor::skipDuplicates
+    \brief Indicates whether duplicate reading values should be omitted.
+    \since 5.1
+
+    When duplicate skipping is enabled, successive readings with the same or very
+    similar values are omitted. This helps reducing the amount of processing done, as less sensor
+    readings are made available. As a consequence, readings arrive at an irregular interval.
+
+    Duplicate skipping is not just enabled for readings that are exactly the same, but also for
+    readings that are quite similar, as each sensor has a bit of jitter even if the device is
+    not moved.
+
+    Support for this property depends on the backend. Use isFeatureSupported() to check if it is
+    supported on the current platform.
+
+    Duplicate skipping is disabled by default.
+
+    Duplicate skipping takes effect when the sensor is started, changing the property while the
+    sensor is active has no immediate effect.
+*/
+bool QSensor::skipDuplicates() const
+{
+    Q_D(const QSensor);
+    return d->skipDuplicates;
+}
+
+/*!
+    Sets the duplicate skipping to \a skipDuplicates.
+
+    \since 5.1
+*/
+void QSensor::setSkipDuplicates(bool skipDuplicates)
+{
+    Q_D(QSensor);
+    if (d->skipDuplicates != skipDuplicates) {
+        d->skipDuplicates = skipDuplicates;
+        emit skipDuplicatesChanged(skipDuplicates);
+    }
+}
+
+/*!
+    \fn QSensor::skipDuplicatesChanged(bool skipDuplicates)
+    \since 5.1
+
+    This signal is emitted when the skipDuplicates property changes.
+*/
+
+/*!
     \property QSensor::availableDataRates
     \brief the data rates that the sensor supports.
 
diff --git a/src/sensors/qsensor.h b/src/sensors/qsensor.h
index f142ca4d..f7162753 100644
--- a/src/sensors/qsensor.h
+++ b/src/sensors/qsensor.h
@@ -93,6 +93,7 @@ class Q_SENSORS_EXPORT QSensor : public QObject
     Q_PROPERTY(QString description READ description)
     Q_PROPERTY(int error READ error NOTIFY sensorError)
     Q_PROPERTY(bool alwaysOn READ isAlwaysOn WRITE setAlwaysOn NOTIFY alwaysOnChanged REVISION 1)
+    Q_PROPERTY(bool skipDuplicates READ skipDuplicates WRITE setSkipDuplicates NOTIFY skipDuplicatesChanged)
 #ifdef Q_QDOC
     Q_PROPERTY(int maxBufferSize)
     Q_PROPERTY(int efficientBufferSize)
@@ -105,6 +106,7 @@ public:
         GeoValues,
         FieldOfView,
         AccelerationMode,
+        SkipDuplicates,
         Reserved = 257 // Make sure at least 2 bytes are used for the enum to avoid breaking BC later
     };
 
@@ -127,6 +129,9 @@ public:
     bool isAlwaysOn() const;
     void setAlwaysOn(bool alwaysOn);
 
+    bool skipDuplicates() const;
+    void setSkipDuplicates(bool skipDuplicates);
+
     qrangelist availableDataRates() const;
     int dataRate() const;
     void setDataRate(int rate);
@@ -169,6 +174,7 @@ Q_SIGNALS:
     void availableSensorsChanged();
     void alwaysOnChanged();
     void dataRateChanged();
+    void skipDuplicatesChanged(bool skipDuplicates);
 
 protected:
     explicit QSensor(const QByteArray &type, QSensorPrivate &dd, QObject* parent = 0);
diff --git a/src/sensors/qsensor_p.h b/src/sensors/qsensor_p.h
index 80312b65..8504a3f6 100644
--- a/src/sensors/qsensor_p.h
+++ b/src/sensors/qsensor_p.h
@@ -79,6 +79,7 @@ public:
         , cache_reading(0)
         , error(0)
         , alwaysOn(false)
+        , skipDuplicates(false)
     {
     }
 
@@ -108,6 +109,7 @@ public:
     int error;
 
     bool alwaysOn;
+    bool skipDuplicates;
 };
 
 class QSensorReadingPrivate