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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
* \title Multi Screen
* \example multi-screen
* \examplecategory {Embedded}
* \brief Multi Screen is a desktop-style Wayland compositor for multiple screens.
* \ingroup qtwaylandcompositor-examples
*
* \section1 Introduction
*
* Multi-screen is a desktop-style Wayland compositor example for multiple
* screens.
*
* \image multi-screen.jpg
*
* For an introduction to the basic principles of creating a \l{Qt Wayland Compositor} with Qt,
* see the \l{Minimal QML}{Minimal QML example}.
*
* \section1 Supporting multiple screens
*
* For each available screen on the system, the example creates a \c CompositorScreen, which is
* a subclass of \l WaylandOutput. If there is only one physical screen available, the example
* emulates three screens with dummy data.
*
* \snippet multi-screen/qml/main.qml screens
*
* Each \l WaylandOutput contains a \l{Window}, which is used for containing client content, as
* is the standard setup with \l{Qt Wayland Compositor}. Since each \l Window is isolated from the
* others, we cannot share any Qt Quick items between them. Therefore, when a client connects and
* a \l ShellSurface is created, one \l ShellSurfaceItem is created on each of the screens.
*
* \snippet multi-screen/qml/main.qml createShellSurfaceItems
*
* These items serve as views of the same client content. The client's surface itself will only be
* created once, and will be shared by the surface items.
*
* Top-level surface items are created as children of the background \l Rectangle in each of the
* outputs. These views are stored for later, and if the client spawns any child windows, these are
* parented to the top-level window's item.
*
* \snippet multi-screen/qml/main.qml parenting
*
* The client content will be visible only on one or two screens at a time. \l ShellSurfaceItem
* positions are synchronized so that when windows enter one screen, they are moved off of another
* at the same time. This gives the appearance of a single item which moves seamlessly between
* screens. The global position of the client is stored in a shared
* \l{ShellSurfaceItem::moveItem}{moveItem} and relative position of each screen's
* \l ShellSurfaceItem is calculated based on this. If the \c moveItem is currently outside the
* bounds of one screen, its coordinates will reflect this, and it will not be visible on that
* screen.
*
* \snippet multi-screen/qml/Chrome.qml position sync
*
* Finally, \l{WaylandQuickItem::setPrimary()} is called at appropriate times to set the primary
* view for the \l ShellSurface, which is used when the client asks to be maximized or fullscreen.
* The primary \l ShellSurfaceItem is selected based on how much of it is currently visible.
*
* \note In order to support multiple Wayland outputs in the same compositor, the
* \l Qt::AA_ShareOpenGLContexts attribute must be set before the \l QGuiApplication
* object is constructed. In the example, we do this at the very beginning of the \c main()
* function.
*
* \snippet multi-screen/main.cpp share context
*
* \sa {Multi Output}
*/
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