9 files changed, 71 insertions, 16 deletions
diff --git a/src/plugins/sensors/ios/iosaccelerometer.h b/src/plugins/sensors/ios/iosaccelerometer.h
index 578501fa..620015f2 100644
--- a/src/plugins/sensors/ios/iosaccelerometer.h
+++ b/src/plugins/sensors/ios/iosaccelerometer.h
@@ -62,6 +62,8 @@ private:
     CMMotionManager *m_motionManager;
     QAccelerometerReading m_reading;
     int m_timer;
+
+    static int s_startCount;
 };
 QT_END_NAMESPACE
 
diff --git a/src/plugins/sensors/ios/iosaccelerometer.mm b/src/plugins/sensors/ios/iosaccelerometer.mm
index a497d7b4..2d2e27ae 100644
--- a/src/plugins/sensors/ios/iosaccelerometer.mm
+++ b/src/plugins/sensors/ios/iosaccelerometer.mm
@@ -46,6 +46,8 @@ char const * const IOSAccelerometer::id("ios.accelerometer");
 
 QT_BEGIN_NAMESPACE
 
+int IOSAccelerometer::s_startCount = 0;
+
 IOSAccelerometer::IOSAccelerometer(QSensor *sensor)
     : QSensorBackend(sensor)
     , m_motionManager([QIOSMotionManager sharedManager])
@@ -58,16 +60,24 @@ IOSAccelerometer::IOSAccelerometer(QSensor *sensor)
 
 void IOSAccelerometer::start()
 {
+    if (m_timer != 0)
+        return;
+
     int hz = sensor()->dataRate();
     m_timer = startTimer(1000 / (hz == 0 ? 60 : hz));
-    [m_motionManager startAccelerometerUpdates];
+    if (++s_startCount == 1)
+        [m_motionManager startAccelerometerUpdates];
 }
 
 void IOSAccelerometer::stop()
 {
-    [m_motionManager stopAccelerometerUpdates];
+    if (m_timer == 0)
+        return;
+
     killTimer(m_timer);
     m_timer = 0;
+    if (--s_startCount == 0)
+        [m_motionManager stopAccelerometerUpdates];
 }
 
 void IOSAccelerometer::timerEvent(QTimerEvent *)
diff --git a/src/plugins/sensors/ios/ioscompass.mm b/src/plugins/sensors/ios/ioscompass.mm
index 34eb0aa7..7fc48d36 100644
--- a/src/plugins/sensors/ios/ioscompass.mm
+++ b/src/plugins/sensors/ios/ioscompass.mm
@@ -71,8 +71,8 @@ QT_BEGIN_NAMESPACE
     quint64 timestamp = quint64(newHeading.timestamp.timeIntervalSinceReferenceDate * 1e6);
     double accuracy = newHeading.headingAccuracy;
     // Accuracy is the maximum number of degrees the reading can be off. The QtSensors scale
-    // goes from 1 to 0, with 1 being the best (0 degrees off), and 0 worst (365 degrees off):
-    qreal calibrationLevel = (accuracy < 0) ? 0 : qMax(0., 1 - (accuracy / 365));
+    // goes from 1 to 0, with 1 being the best (0 degrees off), and 0 worst (360 degrees off):
+    qreal calibrationLevel = (accuracy < 0) ? 0 : qMax(0., 1 - (accuracy / 360));
     qreal heading = qreal(newHeading.magneticHeading);
     m_iosCompass->headingChanged(heading, timestamp, calibrationLevel);
 }
diff --git a/src/plugins/sensors/ios/iosgyroscope.h b/src/plugins/sensors/ios/iosgyroscope.h
index e686240a..d8ff04a1 100644
--- a/src/plugins/sensors/ios/iosgyroscope.h
+++ b/src/plugins/sensors/ios/iosgyroscope.h
@@ -62,6 +62,8 @@ private:
     CMMotionManager *m_motionManager;
     QGyroscopeReading m_reading;
     int m_timer;
+
+    static int s_startCount;
 };
 QT_END_NAMESPACE
 
diff --git a/src/plugins/sensors/ios/iosgyroscope.mm b/src/plugins/sensors/ios/iosgyroscope.mm
index fc9b6166..19e65e57 100644
--- a/src/plugins/sensors/ios/iosgyroscope.mm
+++ b/src/plugins/sensors/ios/iosgyroscope.mm
@@ -44,6 +44,8 @@ char const * const IOSGyroscope::id("ios.gyroscope");
 
 QT_BEGIN_NAMESPACE
 
+int IOSGyroscope::s_startCount = 0;
+
 IOSGyroscope::IOSGyroscope(QSensor *sensor)
     : QSensorBackend(sensor)
     , m_motionManager([QIOSMotionManager sharedManager])
@@ -56,16 +58,24 @@ IOSGyroscope::IOSGyroscope(QSensor *sensor)
 
 void IOSGyroscope::start()
 {
+    if (m_timer != 0)
+        return;
+
     int hz = sensor()->dataRate();
     m_timer = startTimer(1000 / (hz == 0 ? 60 : hz));
-    [m_motionManager startGyroUpdates];
+    if (++s_startCount == 1)
+        [m_motionManager startGyroUpdates];
 }
 
 void IOSGyroscope::stop()
 {
-    [m_motionManager stopGyroUpdates];
+    if (m_timer == 0)
+        return;
+
     killTimer(m_timer);
     m_timer = 0;
+    if (--s_startCount == 0)
+        [m_motionManager stopGyroUpdates];
 }
 
 void IOSGyroscope::timerEvent(QTimerEvent *)
diff --git a/src/plugins/sensors/ios/iosmagnetometer.h b/src/plugins/sensors/ios/iosmagnetometer.h
index 04cbce14..00d921e8 100644
--- a/src/plugins/sensors/ios/iosmagnetometer.h
+++ b/src/plugins/sensors/ios/iosmagnetometer.h
@@ -66,6 +66,9 @@ private:
     QMagnetometerReading m_reading;
     int m_timer;
     bool m_returnGeoValues;
+
+    static int s_magnetometerStartCount;
+    static int s_deviceMotionStartCount;
 };
 QT_END_NAMESPACE
 
diff --git a/src/plugins/sensors/ios/iosmagnetometer.mm b/src/plugins/sensors/ios/iosmagnetometer.mm
index 6bbad60b..98bef2dd 100644
--- a/src/plugins/sensors/ios/iosmagnetometer.mm
+++ b/src/plugins/sensors/ios/iosmagnetometer.mm
@@ -44,6 +44,9 @@ QT_BEGIN_NAMESPACE
 
 char const * const IOSMagnetometer::id("ios.magnetometer");
 
+int IOSMagnetometer::s_magnetometerStartCount = 0;
+int IOSMagnetometer::s_deviceMotionStartCount = 0;
+
 IOSMagnetometer::IOSMagnetometer(QSensor *sensor)
     : QSensorBackend(sensor)
     , m_motionManager([QIOSMotionManager sharedManager])
@@ -61,24 +64,37 @@ IOSMagnetometer::IOSMagnetometer(QSensor *sensor)
 
 void IOSMagnetometer::start()
 {
+    if (m_timer != 0)
+        return;
+
     int hz = sensor()->dataRate();
     m_timer = startTimer(1000 / (hz == 0 ? 60 : hz));
     m_returnGeoValues = static_cast<QMagnetometer *>(sensor())->returnGeoValues();
 
-    if (m_returnGeoValues)
-        [m_motionManager startDeviceMotionUpdates];
-    else
-        [m_motionManager startMagnetometerUpdates];
+    if (m_returnGeoValues) {
+        if (++s_deviceMotionStartCount == 1)
+            [m_motionManager startDeviceMotionUpdates];
+    } else {
+        if (++s_magnetometerStartCount == 1)
+            [m_motionManager startMagnetometerUpdates];
+    }
 }
 
 void IOSMagnetometer::stop()
 {
-    if (m_returnGeoValues)
-        [m_motionManager stopDeviceMotionUpdates];
-    else
-        [m_motionManager stopMagnetometerUpdates];
+    if (m_timer == 0)
+        return;
+
     killTimer(m_timer);
     m_timer = 0;
+
+    if (m_returnGeoValues) {
+        if (--s_deviceMotionStartCount == 0)
+            [m_motionManager stopDeviceMotionUpdates];
+    } else {
+        if (--s_magnetometerStartCount == 0)
+            [m_motionManager stopMagnetometerUpdates];
+    }
 }
 
 void IOSMagnetometer::timerEvent(QTimerEvent *)
diff --git a/src/plugins/sensors/ios/iosproximitysensor.h b/src/plugins/sensors/ios/iosproximitysensor.h
index c024e021..99f9564e 100644
--- a/src/plugins/sensors/ios/iosproximitysensor.h
+++ b/src/plugins/sensors/ios/iosproximitysensor.h
@@ -64,6 +64,8 @@ public:
 private:
     ProximitySensorCallback *m_proximitySensorCallback;
     QProximityReading m_reading;
+
+    static int s_startCount;
 };
 QT_END_NAMESPACE
 
diff --git a/src/plugins/sensors/ios/iosproximitysensor.mm b/src/plugins/sensors/ios/iosproximitysensor.mm
index 6a2465bf..eae85608 100644
--- a/src/plugins/sensors/ios/iosproximitysensor.mm
+++ b/src/plugins/sensors/ios/iosproximitysensor.mm
@@ -45,6 +45,8 @@ char const * const IOSProximitySensor::id("ios.proximitysensor");
 
 QT_BEGIN_NAMESPACE
 
+int IOSProximitySensor::s_startCount = 0;
+
 @interface ProximitySensorCallback : NSObject
 {
     IOSProximitySensor *m_iosProximitySensor;
@@ -110,8 +112,12 @@ IOSProximitySensor::~IOSProximitySensor()
 
 void IOSProximitySensor::start()
 {
+    if (m_proximitySensorCallback)
+        return;
+
     m_proximitySensorCallback = [[ProximitySensorCallback alloc] initWithQIOSProximitySensor:this];
-    [UIDevice currentDevice].proximityMonitoringEnabled = YES;
+    if (++s_startCount == 1)
+        [UIDevice currentDevice].proximityMonitoringEnabled = YES;
 }
 
 void IOSProximitySensor::proximityChanged(bool close)
@@ -123,9 +129,13 @@ void IOSProximitySensor::proximityChanged(bool close)
 
 void IOSProximitySensor::stop()
 {
-    [UIDevice currentDevice].proximityMonitoringEnabled = NO;
+    if (!m_proximitySensorCallback)
+        return;
+
     [m_proximitySensorCallback release];
     m_proximitySensorCallback = 0;
+    if (--s_startCount == 0)
+        [UIDevice currentDevice].proximityMonitoringEnabled = NO;
 }
 
 QT_END_NAMESPACE