3 files changed, 41 insertions, 14 deletions

diff --git a/src/sensors/qsensor.cpp b/src/sensors/qsensor.cpp
index 8d670bb7..a0724ae8 100644
--- a/src/sensors/qsensor.cpp
+++ b/src/sensors/qsensor.cpp
@@ -263,19 +263,22 @@ bool QSensor::connectToBackend()
     if (isConnectedToBackend())
         return true;
 
+    int dataRate = d->dataRate;
+    int outputRange = d->outputRange;
+
     d->backend = QSensorManager::createBackend(this);
 
-    // Reset the properties to their default values and re-set them now so
-    // that the logic we've put into the setters gets called.
-    if (d->dataRate != 0) {
-        int tmp = d->dataRate;
-        d->dataRate = 0;
-        setDataRate(tmp);
-    }
-    if (d->outputRange != -1) {
-        int tmp = d->outputRange;
-        d->outputRange = -1;
-        setOutputRange(tmp);
+    if (d->backend) {
+        // Reset the properties to their default values and re-set them now so
+        // that the logic we've put into the setters gets called.
+        if (dataRate != 0) {
+            d->dataRate = 0;
+            setDataRate(dataRate);
+        }
+        if (outputRange != -1) {
+            d->outputRange = -1;
+            setOutputRange(outputRange);
+        }
     }
 
     return isConnectedToBackend();
diff --git a/src/sensors/qsensorbackend.cpp b/src/sensors/qsensorbackend.cpp
index a576e5b9..7c65c59b 100644
--- a/src/sensors/qsensorbackend.cpp
+++ b/src/sensors/qsensorbackend.cpp
@@ -224,8 +224,7 @@ void QSensorBackend::addDataRate(qreal min, qreal max)
     setDataRates(otherSensor);
     \endcode
 
-    Note that this function should be called from the constructor so that the information
-    is available immediately.
+    Note that this function must be called from the constructor.
 
     \sa QSensor::availableDataRates, addDataRate()
 */
@@ -239,9 +238,12 @@ void QSensorBackend::setDataRates(const QSensor *otherSensor)
         qWarning() << "ERROR: Cannot call QSensorBackend::setDataRates with an invalid sensor";
         return;
     }
+    if (m_sensor->isConnectedToBackend()) {
+        qWarning() << "ERROR: Cannot call QSensorBackend::setDataRates outside of the constructor";
+        return;
+    }
     QSensorPrivate *d = m_sensor->d_func();
     d->availableDataRates = otherSensor->availableDataRates();
-    d->dataRate = otherSensor->dataRate();
 }
 
 /*!
diff --git a/tests/auto/qsensor/tst_qsensor.cpp b/tests/auto/qsensor/tst_qsensor.cpp
index 92cb281a..8025ab21 100644
--- a/tests/auto/qsensor/tst_qsensor.cpp
+++ b/tests/auto/qsensor/tst_qsensor.cpp
@@ -353,6 +353,28 @@ private slots:
             QCOMPARE(actual, expected);
         }
 
+        // Test that a previously-set, valid data rate is retained
+        {
+            TestSensor sensor;
+            sensor.setDataRate(100);
+            sensor.setProperty("doThis", "rates");
+            sensor.connectToBackend();
+            int actual = sensor.dataRate();
+            int expected = 100;
+            QCOMPARE(actual, expected);
+        }
+
+        // Test that a previously-set, invalid data rate is reset to 0
+        {
+            TestSensor sensor;
+            sensor.setDataRate(50);
+            sensor.setProperty("doThis", "rates");
+            sensor.connectToBackend();
+            int actual = sensor.dataRate();
+            int expected = 0;
+            QCOMPARE(actual, expected);
+        }
+
         {
             TestSensor sensor;
             sensor.setProperty("doThis", "rates(0)");