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// Copyright (C) 2019 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\example scenegraph/metalunderqml
\title Scene Graph - Metal Under QML
\ingroup qtquickexamples
\brief Shows how to render directly with Metal under a Qt Quick scene.
\image metalunderqml-example.jpg
The Metal Under QML example shows how an application can make use
of the \l QQuickWindow::beforeRendering() and \l
QQuickWindow::beforeRenderPassRecording() signals to draw custom
Metal content under a Qt Quick scene. This signal is emitted at
the start of every frame, before the scene graph starts its
rendering, thus any Metal draw calls that are made as a response
to this signal, will stack under the Qt Quick items. There are two
signals, because the custom Metal commands are recorded onto the
same command buffer with the same render command encoder that the
scene graph uses. beforeRendering() on its own is not sufficient
for this because it gets emitted at the start of the frame, before
having an
\l{https://developer.apple.com/documentation/metal/mtlrendercommandencoder}{MTLRenderCommandEncoder}
available. By also connecting to beforeRenderPassRecording(), the
application can gain access to the necessary native objects.
As an alternative, applications that wish to render Metal content
on top of the Qt Quick scene, can do so by connecting to the \l
QQuickWindow::afterRendering() and \l
QQuickWindow::afterRenderPassRecording() signals.
In this example, we will also see how it is possible to have
values that are exposed to QML which affect the Metal
rendering. We animate the threshold value using a NumberAnimation
in the QML file and this value is used by the Metal shader
program that draws the squircles.
The example is equivalent in most ways to the \l{Scene Graph - OpenGL Under
QML}{OpenGL Under QML}, \l{Scene Graph - Direct3D 11 Under QML}{Direct3D 11
Under QML}, and \l{Scene Graph - Vulkan Under QML}{Vulkan Under QML}
examples, they all render the same custom content, just via different
native APIs.
*/
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