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>

3 files changed, 59 insertions, 0 deletions

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