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/****************************************************************************
**
** Copyright (C) 2019 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
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**
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** Documentation License version 1.3 as published by the Free Software
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** this file. Please review the following information to ensure
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/*!
\example scenegraph/vulkanunderqml
\title Scene Graph - Vulkan Under QML
\ingroup qtquickexamples
\brief Shows how to render directly with vulkan under a Qt Quick scene.
\image vulkanunderqml-example.jpg
The Vulkan Under QML example shows how an application can make use of the
\l QQuickWindow::beforeRendering() and \l
QQuickWindow::beforeRenderPassRecording() signals to draw custom Vulkan
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 Vulkan
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 Vulkan commands
are recorded onto the same command buffer that is used by the scene graph.
beforeRendering() on its own is not sufficient for this because it gets
emitted at the start of the frame, before recording the start of a
renderpass instance via
\l{https://www.khronos.org/registry/vulkan/specs/1.1-extensions/man/html/vkCmdBeginRenderPass.html}{vkCmdBeginRenderPass}.
By also connecting to beforeRenderPassRecording(), the application's own
commands and the scene graph's scaffolding will end up in the right order.
As an alternative, applications that wish to render Vulkan 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 Vulkan
rendering. We animate the threshold value using a NumberAnimation
in the QML file and this value is used by the SPIR-V 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 - Metal Under QML}{Metal Under QML}
examples, they all render the same custom content, just via different
native APIs.
*/
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