Add API for duplicate skipping.

Change-Id: I4569993e2689f607c2b771438ed5e1ba879691b9
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

4 files changed, 57 insertions, 1 deletions

diff --git a/plugins/declarative/sensors/sensors.cpp b/plugins/declarative/sensors/sensors.cpp
index 500e680eeb..ae1e147e23 100644
--- a/plugins/declarative/sensors/sensors.cpp
+++ b/plugins/declarative/sensors/sensors.cpp
@@ -192,6 +192,13 @@ Q_EXPORT_PLUGIN2(qsensorsdeclarativemodule, QT_PREPEND_NAMESPACE(QSensorsDeclara
 */
 
 /*!
+    \qmlproperty bool Sensor::skipDuplicates
+    Omitts readings with the same or very similar values.
+    \sa QSensor::skipDuplicates
+    \since Mobility 1.3
+*/
+
+/*!
     \qmlproperty SensorReading Sensor::reading
     \since Mobility 1.2
     Holds the most recent sensor reading.
diff --git a/src/sensors/qsensor.cpp b/src/sensors/qsensor.cpp
index 0b22ad20f7..e9637fb06c 100644
--- a/src/sensors/qsensor.cpp
+++ b/src/sensors/qsensor.cpp
@@ -399,6 +399,48 @@ bool QSensor::isAlwaysOn() const
 }
 
 /*!
+    \property QSensor::skipDuplicates
+    \brief Indicates whether duplicate reading values should be omitted.
+
+    When duplicate skipping is enabled, successive readings with the same or very
+    similar values are omitted and skipped. 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. It is disabled by default.
+
+    Duplicate skipping can only be changed while the sensor is not active.
+*/
+bool QSensor::skipDuplicates() const
+{
+    Q_D(const QSensor);
+    return d->skipDuplicates;
+}
+
+/*!
+    Sets the duplicate skipping to \a skipDuplicates.
+*/
+void QSensor::setSkipDuplicates(bool skipDuplicates)
+{
+    Q_D(QSensor);
+    if (d->skipDuplicates != skipDuplicates) {
+        d->skipDuplicates = skipDuplicates;
+        emit skipDuplicatesChanged(skipDuplicates);
+    }
+}
+
+/*!
+    \fn skipDuplicatesChanged(bool skipDuplicates)
+
+    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 02ef032e90..21eaf07425 100644
--- a/src/sensors/qsensor.h
+++ b/src/sensors/qsensor.h
@@ -98,7 +98,8 @@ class Q_SENSORS_EXPORT QSensor : public QObject
     Q_PROPERTY(int outputRange READ outputRange WRITE setOutputRange)
     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 alwaysOn READ isAlwaysOn WRITE setAlwaysOn NOTIFY alwaysOnChanged)
+    Q_PROPERTY(bool skipDuplicates READ skipDuplicates WRITE setSkipDuplicates NOTIFY skipDuplicatesChanged)
 #ifdef Q_QDOC
     Q_PROPERTY(int maxBufferSize)
     Q_PROPERTY(int efficientBufferSize)
@@ -124,6 +125,9 @@ 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);
@@ -163,6 +167,7 @@ Q_SIGNALS:
     void sensorError(int error);
     void availableSensorsChanged();
     void alwaysOnChanged();
+    void skipDuplicatesChanged(bool skipDuplicates);
 
 protected:
     // called by the back end
diff --git a/src/sensors/qsensor_p.h b/src/sensors/qsensor_p.h
index de34cd02df..1aa3fdef16 100644
--- a/src/sensors/qsensor_p.h
+++ b/src/sensors/qsensor_p.h
@@ -75,6 +75,7 @@ public:
         , cache_reading(0)
         , error(0)
         , alwaysOn(false)
+        , skipDuplicates(false)
     {
     }
 
@@ -102,6 +103,7 @@ public:
     int error;
 
     bool alwaysOn;
+    bool skipDuplicates;
 };
 
 class QSensorReadingPrivate