Add a simple Torch class that wraps the camera flash.

Since nearly all programmable torch hardware doubles as camera flash
hardware, offer this class here that wraps the QCameraFlashControl.

Change-Id: Ib2c061c21c14221d67477d8a3fd89a76fc26ed71
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>

src/imports/multimedia/qdeclarativetorch.cpp

@@ -0,0 +1,184 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** GNU Lesser General Public License Usage
+** This file may be used under the terms of the GNU Lesser General Public
+** License version 2.1 as published by the Free Software Foundation and
+** appearing in the file LICENSE.LGPL included in the packaging of this
+** file. Please review the following information to ensure the GNU Lesser
+** General Public License version 2.1 requirements will be met:
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU General
+** Public License version 3.0 as published by the Free Software Foundation
+** and appearing in the file LICENSE.GPL included in the packaging of this
+** file. Please review the following information to ensure the GNU General
+** Public License version 3.0 requirements will be met:
+** http://www.gnu.org/copyleft/gpl.html.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QDebug>
+#include <QMediaService>
+
+#include "qdeclarativetorch_p.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \qmlclass Torch QDeclarativeTorch
+    \brief The Torch element provides simple control over torch functionality
+
+    \ingroup multimedia_qml
+
+    This element is part of the \bold{QtMultimedia 5.0} module.
+
+    In many cases the torch hardware is shared with camera flash functionality,
+    and might be automatically controlled by the device.  You have control over
+    the power level (of course, higher power levels are brighter but reduce
+    battery life significantly).
+
+    \qml
+    import QtQuick 2.0
+    import QtMultimedia 5.0
+
+    Torch {
+        power: 75       // 75% of full power
+        enabled: true   // On
+    }
+
+    \endqml
+*/
+QDeclarativeTorch::QDeclarativeTorch(QObject *parent)
+    : QObject(parent)
+{
+    m_camera = new QCamera(this);
+    QMediaService *service = m_camera->service();
+
+    m_exposure = service ? service->requestControl<QCameraExposureControl*>() : 0;
+    m_flash = service ? service->requestControl<QCameraFlashControl*>() : 0;
+
+    if (m_exposure)
+        connect(m_exposure, SIGNAL(exposureParameterChanged(int)), SLOT(parameterChanged(int)));
+
+    // XXX There's no signal for flash mode changed
+}
+
+QDeclarativeTorch::~QDeclarativeTorch()
+{
+}
+
+/*!
+    \qmlproperty bool Torch::enabled
+    \property QDeclarativeTorch::enabled
+
+    Whether the torch is on.  If the torch functionality is shared
+    with the camera flash hardware, the camera will take priority
+    over torch settings and the torch may be disabled.
+*/
+/*!
+    Returns whether the torch is on.  If the torch functionality
+    is shared with the camera flash hardware, the camera will take
+    priority and the torch may be disabled.
+ */
+bool QDeclarativeTorch::enabled() const
+{
+    if (!m_flash)
+        return false;
+
+    return m_flash->flashMode() & QCameraExposure::FlashTorch;
+}
+
+
+/*!
+    If \a on is true, attempt to turn on the torch.
+    If the torch hardware is already in use by the camera, this will
+    be ignored.
+*/
+void QDeclarativeTorch::setEnabled(bool on)
+{
+    if (!m_flash)
+        return;
+
+    QCameraExposure::FlashModes mode = m_flash->flashMode();
+
+    if (mode & QCameraExposure::FlashTorch) {
+        if (!on) {
+            m_flash->setFlashMode(mode & ~QCameraExposure::FlashTorch);
+            emit enabledChanged();
+        }
+    } else {
+        if (on) {
+            m_flash->setFlashMode(mode | QCameraExposure::FlashTorch);
+            emit enabledChanged();
+        }
+    }
+}
+
+/*!
+    \qmlproperty int Torch::power
+    \property QDeclarativeTorch::power
+
+    The current torch power setting, as a percentage of full power.
+
+    In some cases this setting may change automatically as a result
+    of temperature or battery conditions.
+*/
+/*!
+    Returns the current torch power settings, as a percentage of full power.
+*/
+int QDeclarativeTorch::power() const
+{
+    if (!m_exposure)
+        return 0;
+
+    return m_exposure->exposureParameter(QCameraExposureControl::FlashPower).toInt();
+}
+
+/*!
+    Sets the current torch power setting to \a power, as a percentage of
+    full power.
+*/
+void QDeclarativeTorch::setPower(int power)
+{
+    if (!m_exposure)
+        return;
+
+    power = qBound(0, power, 100);
+    if (this->power() != power) {
+        m_exposure->setExposureParameter(QCameraExposureControl::FlashPower, power);
+        emit powerChanged();
+    }
+}
+
+/* Check for changes in flash power */
+void QDeclarativeTorch::parameterChanged(int parameter)
+{
+    if (parameter == QCameraExposureControl::FlashPower) {
+        emit powerChanged();
+    }
+}
+
+QT_END_NAMESPACE
+