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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 Fancy Compositor
\example fancy-compositor
\examplecategory {Embedded}
\brief Fancy Compositor is an example that demonstrates how to write a fancy Wayland compositor in pure QML.
\ingroup qtwaylandcompositor-examples
\section1 Introduction
Fancy Compositor is a small desktop-style Wayland compositor example that demonstrates the power and
ease of the \l{Qt Wayland Compositor} QML APIs.
The Fancy Compositor example is similar to the \l{Minimal QML}{Minimal QML example}, in that it is a
full-blown Wayland compositor, implemented only using QML code.
\section1 Initializing the Compositor
Like the \l{Minimal QML}{Minimal QML example}, Fancy Compositor supports the main
\l{Shell Extensions - Qt Wayland Compositor}{shell extensions} that are supported by Qt.
\snippet fancy-compositor/qml/main.qml shell extensions
These are instantiated as children of the \l{WaylandCompositor} which automatically adds
them to the list of supported interfaces which is broadcasted to clients from the server.
When a connected client creates a surface and binds it to one of the shell extensions, the
corresponding signal is emitted. This then calls a method inside our custom \l WaylandOutput
class, which appends the \l ShellSurface to a \l{ListModel}.
\snippet fancy-compositor/qml/CompositorScreen.qml handleShellSurface
This model is used as the source for a \l Repeater which creates
\l{ShellSurfaceItem}{ShellSurfaceItems} inside the compositor's \l WaylandOutput. This adds a
view of the surface in the Qt Quick scene. Since it is a \l{ShellSurfaceItem}, it also has
certain interaction options for the user of the compositor, depending on which shell extension
is in use.
\snippet fancy-compositor/qml/CompositorScreen.qml repeater
\section1 Keyboard
In addition to the basic windowing system functions, the Fancy Compositor also supports an
optional on-screen keyboard running in-process. This uses the \l{Qt Virtual Keyboard} module,
and will be enabled if the module is available.
\snippet fancy-compositor/qml/Keyboard.qml keyboard
The code is simple. We instantiate an \l InputPanel in the bottom of the output, and make sure
it is visible if and only if it is currently active.
\snippet fancy-compositor/qml/CompositorScreen.qml keyboard
The keyboard is then added to the \l WaylandOutput using a \l Loader element. The \l Loader is
used here to avoid having a hard dependency on the \l{Qt Virtual Keyboard} module. If loading
fails, then the compositor will continue operating normally, but without support for an
on-screen keyboard.
Finally, we need a way for the compositor to communicate the text input to its clients. This
is done via a \c{text-input} extension. The Fancy Compositor example supports both the
\c{text_input_unstable_v2} protocol as well as Qt's \c{qt_text_input_method_unstable_v1}
protocol.
\snippet fancy-compositor/qml/main.qml text input
The \c{qt_text_input_method_unstable_v1} extension is added to the compositor by instantiating
the \l QtTextInputMethodManager as a child of the \l{WaylandCompositor}, and
\l{TextInputManager} adds \c{text_input_unstable_v2}.
Newer Qt applications will pick \c{qt_text_input_method_unstable_v1} when it is available,
while other clients can use \c{text_input_unstable_v2}.
\section1 Transitions
In addition to the basic functionality, the Fancy Compositor example also demonstrates animated
transitions between states.
The first of these is the \e{activation} transition. This is only supported on the \l{XdgShell},
since this is the only shell extension which has an \l{XdgToplevel::}{activated} state.
\snippet fancy-compositor/qml/Chrome.qml activation
When a client window becomes activated under the \l XdgShell protocol, we trigger an animation
which makes the window "pop out" for 200 ms.
The Fancy Compositor also supports a \e{destruction} animation. This triggers whenever the
window closes and surface is destroyed, whether this was because the client gracefully closed
its window, or even if it crashes.
\snippet fancy-compositor/qml/Chrome.qml destruction
To ensure that the content exists for the duration of the animation, we start by locking the
buffer. This means the final frame rendered by the client will remain in memory until we are
done with it.
Again, we trigger an animation on the scale of the item. The animation in question imitates
turning off the power on a CRT screen, giving a visual clue to the user that the window is
closing, and didn't just vanish into thin air.
Any sort of animated effect may be used for state changes such as these, with the full range
of Qt Quick at your disposal.
*/
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