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/*!
\example multimedia/video/qmlvideo
\title QML Video Example
\ingroup multimedia_examples

\brief The QML Video Example demonstrates the various manipulations (move;
resize; rotate; change aspect ratio) which can be applied to QML \l{VideoOutput}
items.

\section1 Overview

This example demonstrates the various manipulations (move; resize; rotate;
change aspect ratio) which can be applied to QML \l{VideoOutput} items.

It also shows how native code can be combined with QML to implement more
advanced functionality - in this case, C++ code is used to calculate the QML
frame rate.  This value is rendered in QML in a semi-transparent item
overlaid on the video content.

The following image shows the application executing the video-overlay scene,
which creates a dummy overlay item (just a semi-transparent \l{Rectangle}),
which moves across the \l{VideoOutput} item.

\image qmlvideo-overlay.png

\section1 Application structure

The \l{multimedia/video/qmlvideo/qml/qmlvideo/main.qml} file creates a UI which includes
the following items:

\list
    \li Two \l{multimedia/video/qmlvideo/qml/qmlvideo/Button.qml}{Button} instances, each
       of which displays a filename, and can be used to launch a
       \l{multimedia/video/qmlvideo/qml/qmlvideo/FileBrowser.qml}{FileBrowser}
    \li An exit \l{multimedia/video/qmlvideo/qml/qmlvideo/Button.qml}{Button}
    \li A \l{multimedia/video/qmlvideo/qml/qmlvideo/SceneSelectionPanel.qml}{SceneSelectionPanel},
       which is a flickable list displaying the available scenes
    \li At the lower left, an item which displays the QML repainting rate - the
       upper number is the instantaneous frame rate and the lower number is the
       average over the past second.
\endlist

\image qmlvideo-menu.png

Each scene in the flickable list is implemented in its own QML file - for
example the video-basic scene (which just displays a static \l{VideoOutput}
in the center of the screen) is implemented in the
\l{multimedia/ideo/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic.qml} file.  As you
can see from the code, this makes use of a type of inheritance: a
\l{multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic} item ...

\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml
\skipto import
\printuntil /^\}/

... is-a
\l{multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml}{SceneBasic} ...

\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml
\skipto import
\printuntil contentType
\dots
\skipto Content
\printuntil content
\dots
\skipto }
\printuntil /^\}/

... which is-a
\l{multimedia/video/qmlvideo/qml/qmlvideo/Scene.qml}{Scene}:

\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/Scene.qml
\skipto import
\printuntil root
\dots
\skipto property QtObject content
\printuntil content
\dots
\skipto Button
\printuntil /^\}/

\l{multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml}{SceneBasic} describes the
structure and behaviour of the scene, but is agnostic of the type of content
which will be displayed - this is abstracted by
\l{multimedia/video/qmlvideo/qml/qmlvideo/Content.qml}{Content}.

This pattern allows us to define a particular use case (in this case, simply
display a static piece of content), and then instantiate that use case for
both video content
(\l{multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic}) and cameracontent
(\l{multimedia/video/qmlvideo/qml/qmlvideo/CameraBasic.qml}{CameraBasic}).  This approach
is used to implement many of the other scenes - for example, "repeatedly slide
the content from left to right and back again" is implemented by
\l{multimedia/video/qmlvideo/qml/qmlvideo/SceneMove.qml}{SceneMove}, on which
\l{multimedia/video/qmlvideo/qml/qmlvideo/VideoMove.qml}{VideoMove} and
\l{multimedia/video/qmlvideo/qml/qmlvideo/CameraMove.qml}{CameraMove} are based.

Depending on the value of the contentType property in the top-level scene
instance, the embedded
\l{multimedia/video/qmlvideo/qml/qmlvideo/Content.qml}{Content} item creates either a
\l{MediaPlayer} or a \l{Camera} item.

\section1 Calculating and displaying QML painting rate

\input video-qml-paint-rate.qdocinc

All that remains is to connect the afterRendering() signal of the QQuickView
object to a JavaScript function, which will eventually call frequencyItem.notify():

\quotefromfile multimedia/video/qmlvideo/main.cpp
\skipto QmlApplicationViewer
\printuntil ;
\dots
\skipto QQuickItem
\printuntil ;
\dots
\skipto QObject::connect
\printuntil SLOT(qmlFramePainted()));

*/

