Changes so that sensor.start() does not block (QML)

The C++ library tries to delay things as much as possible. It turns
out that doing this for QML is not optimal because it means calling
sensor.start() can block for a long time (up to hundreds of
milliseconds in worst case scenarious). If the sensor is started
after the UI is visible, this will cause a stutter.

The workaround is not particularly elegant. We force the sensors
library to do its setup while the QML plugin is being loaded.

Change-Id: Iae945ccb79eb568c5decbfdf8a5d623cd96e9d6b
Reviewed-by: Zsolt Simon <zsolt.simon@nokia.com>

2 files changed, 7 insertions, 1 deletions

diff --git a/src/imports/sensors/sensors.cpp b/src/imports/sensors/sensors.cpp
index b81bdd3d..f65af6a2 100644
--- a/src/imports/sensors/sensors.cpp
+++ b/src/imports/sensors/sensors.cpp
@@ -106,6 +106,9 @@ public:
         int major;
         int minor;
 
+        // Force all of the sensors initialization to happen now, while we don't have a UI thread to interrupt
+        (void)QSensor::sensorTypes();
+
         // Register the 1.1 interfaces
         major = 1;
         minor = 1;
diff --git a/src/imports/sensors2/sensors2.cpp b/src/imports/sensors2/sensors2.cpp
index ebcefcfb..190ecde0 100644
--- a/src/imports/sensors2/sensors2.cpp
+++ b/src/imports/sensors2/sensors2.cpp
@@ -57,8 +57,11 @@ public:
     virtual void registerTypes(const char *uri)
     {
         qDebug() << "QSensors2DeclarativeModule::registerTypes(const char *uri)";
-
         Q_ASSERT(QLatin1String(uri) == QLatin1String("QtSensors"));
+
+        // Force all of the sensors initialization to happen now, while we don't have a UI thread to interrupt
+        (void)QSensor::sensorTypes();
+
         qmlRegisterUncreatableType<qsensor2common      >(uri, 5, 0, "Sensor", QLatin1String("Cannot create Sensor"));
         qmlRegisterType           <QSensor2Tilt        >(uri, 5, 0, "TiltSensor");
         qmlRegisterType           <QSensor2AmbientLight>(uri, 5, 0, "AmbientLightSensor");