// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \example planespotter
    \title Plane Spotter (QML)
    \ingroup qtlocation-examples
    \examplecategory {Positioning & Location}
    \brief The \c {Plane Spotter} example demonstrates the tight integration of
    location and positioning data types into QML.

    \image planespotter.png

    The \c {Plane Spotter} example demonstrates how to integrate location and positioning
    related C++ data types into QML and vice versa. This is useful when it is desirable to
    run CPU intensive position calculations in native environments
    but the results are supposed to be displayed using QML.

    The example shows a map of Europe and airplanes on two routes across Europe.
    The first airplane commutes between Oslo and Berlin and the second airplane
    commutes between London and Berlin. The position tracking of each airplane
    is implemented in C++. The Oslo-Berlin plane is piloted in QML and the London-Berlin
    plane is commanded by a C++ pilot.

    \include examples-run.qdocinc

    \section1 Overview


    This example makes use of the \l Q_GADGET feature as part of its position controller
    implementation. It permits \l {Cpp_value_integration_positioning}{direct integration}
    of non-QObject based C++ value types into QML.

    The main purpose of the \c PlaneController class is to track the current
    coordinates of the plane at a given time. It exposes the position
    via its position property.

    \snippet planespotter/main.cpp PlaneController1
    \snippet planespotter/main.cpp PlaneController2

    The example's \c main() function is responsible for the binding of the
    \c PlaneController class instances into the QML context:

    \snippet planespotter/main.cpp PlaneControllerMain

    Similar to QObject derived classes, \l QGeoCoordinate can be integrated without
    an additional QML wrapper.

    \section1 Steering the Planes

    As mentioned above, the primary purpose of \c PlaneController class is to track the current
    positions of the two planes (Oslo-Berlin and London-Berlin) and advertise them as a property
    to the QML layer. Its secondary purpose is to set and progress a plane along a given
    flight path. In a sense it can act as a pilot. This is very much like
    \l CoordinateAnimation which can animate the transition from one geo coordinate to another.
    This example demonstrates how the \c {PlaneController}'s position property is modified
    by C++ code using the PlaneController's own piloting abilities and by QML code using
    \l CoordinateAnimation as pilot. The Oslo-Berlin plane is animated using QML code
    and the London-Berlin plane is animated using C++ code.

    No matter which pilot is used, the results to the pilot's
    actions are visible in C++ and QML and thus the example demonstrates unhindered and direct
    exchange of position data through the C++/QML boundary.

    The visual representation of each \c Plane is done using
    the \l MapQuickItem type which permits the embedding of arbitrary QtQuick items
    into a map:

    \snippet planespotter/Plane.qml PlaneMapQuick1
    \snippet planespotter/Plane.qml PlaneMapQuick2

    \section2 The C++ Pilot

    The C++ plane is steered by C++. The \c from and \c to property of the controller
    class set the origin and destination which the pilot uses to calculate the
    bearing for the plane:

    \snippet planespotter/main.cpp C++Pilot1

    The pilot employs a \l QBasicTimer and \l {QTimerEvent}{QTimerEvents} to
    constantly update the position. During each timer iteration
    \c PlaneController::updatePosition() is called and a new position calculated.

    \snippet planespotter/main.cpp C++Pilot3

    Once the new position is calculated, \c setPosition() is called and
    the subsequent change notification of the property pushes the new position
    to the QML layer.

    The C++ plane is started by clicking on the plane:

    \snippet planespotter/planespotter.qml CppPlane1
    \snippet planespotter/planespotter.qml CppPlane2

    \l {azimuthTo}() calculates the bearing in degrees from one coordinate to another.
    Note that the above code utilizes a QML animation to tie the rotation
    and the position change into a single animation flow:

    \snippet planespotter/planespotter.qml CppPlane3

    First, \l NumberAnimation rotates the plane into the correct direction
    and once that is done the \c startFlight() function takes care of
    starting the plane's position change.

    \snippet planespotter/main.cpp C++Pilot2

    \section2 The QML Pilot

    The \l CoordinateAnimation type is used to control the flight from Oslo
    to Berlin and vice versa. It replaces the above \l ScriptAction.

    \snippet planespotter/planespotter.qml QmlPlane1

    The \l TapHandler of the QML plane implements the logic for the course setting
    and starts the animation when required.

    \snippet planespotter/planespotter.qml QmlPlane2

*/
