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/*!
\example video/qmlvideo
\title QML Video Example
\ingroup multimedia_examples
\brief Transforming video and camera viewfinder content.

\e{QML Video} demonstrates the various transformations (move; resize; rotate;
change aspect ratio) that can be applied to QML \l VideoOutput and \l Camera
types.

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.jpg

\include examples-run.qdocinc

\section1 Application Structure

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

\list
    \li Two \l{video/qmlvideo/qml/qmlvideo/Button.qml}{Button} instances, each
       of which displays a filename, and can be used to launch a
       \l{video/qmlvideo/qml/qmlvideo/FileBrowser.qml}{FileBrowser}
    \li An exit \l{video/qmlvideo/qml/qmlvideo/Button.qml}{Button}
    \li A \l{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.jpg

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{video/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{video/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic} item ...

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

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

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

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

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

\l{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{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{video/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic}) and camera content
(\l{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{video/qmlvideo/qml/qmlvideo/SceneMove.qml}{SceneMove}, on which
\l{video/qmlvideo/qml/qmlvideo/VideoMove.qml}{VideoMove} and
\l{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{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 multimedia/doc/src/examples/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 video/qmlvideo/main.cpp
\skipto QGuiApplication
\printuntil ;
\dots
\skipto QQuickItem
\printuntil ;
\dots
\skipto QObject::connect
\printuntil SLOT(qmlFramePainted()));

*/
