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/****************************************************************************
**
** Copyright (C) 2020 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQuick module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qquickgraphicsconfiguration_p.h"
#if QT_CONFIG(vulkan)
#include <QtGui/private/qrhivulkan_p.h>
#endif
QT_BEGIN_NAMESPACE
/*!
\class QQuickGraphicsConfiguration
\since 6.0
\inmodule QtQuick
\brief The QQuickGraphicsConfiguration class is a container for low-level
graphics settings that can affect how the underlying graphics API, such as
Vulkan, is initialized by the Qt Quick scene graph. It can also control
certain aspects of the scene graph renderer.
When constructing and showing a QQuickWindow that uses Vulkan to render, a
Vulkan instance (\c VkInstance), a physical device (\c VkPhysicalDevice), a
device (\c VkDevice) and associated objects (queues, pools) are initialized
through the Vulkan API. The same is mostly true when using
QQuickRenderControl to redirect the rendering into a custom render target,
such as a texture. While QVulkanInstance construction is under the
application's control then, the initialization of other graphics objects
happen the same way in QQuickRenderControl::initialize() as with an
on-screen QQuickWindow.
For the majority of applications no additional configuration is needed
because Qt Quick provides reasonable defaults for many low-level graphics
settings, for example which device extensions to enable.
This will not alway be sufficient, however. In advanced use cases, when
integrating direct Vulkan or other graphics API content, or when
integrating with an external 3D or VR engine, such as, OpenXR, the
application will want to specify its own set of settings when it comes to
details, such as which device extensions to enable.
That is what this class enables. It allows specifying, for example, a list
of device extensions that is then picked up by the scene graph when using
Vulkan, or graphics APIs where the concept is applicable. Where some
concepts are not applicable, the related settings are simply ignored.
Another class of settings are related to the scene graph's renderer. In
some cases applications may want to control certain behavior,such as using
the depth buffer when rendering 2D content. In Qt 5 such settings were
either not controllable at all, or were managed through environment
variables. In Qt 6, QQuickGraphicsConfiguration provides a new home for
these settings, while keeping support for the legacy environment variables,
where applicable.
\note Setting a QQuickGraphicsConfiguration on a QQuickWindow must happen
early enough, before the scene graph is initialized for the first time for
that window. With on-screen windows this means the call must be done before
invoking show() on the QQuickWindow or QQuickView. With QQuickRenderControl
the configuration must be finalized before calling
\l{QQuickRenderControl::initialize()}{initialize()}.
\sa QQuickWindow::setGraphicsConfiguration(), QQuickWindow, QQuickRenderControl
*/
/*!
Constructs a default QQuickGraphicsConfiguration that does not specify any
additional settings for the scene graph to take into account.
*/
QQuickGraphicsConfiguration::QQuickGraphicsConfiguration()
: d(new QQuickGraphicsConfigurationPrivate)
{
}
/*!
\internal
*/
void QQuickGraphicsConfiguration::detach()
{
qAtomicDetach(d);
}
/*!
\internal
*/
QQuickGraphicsConfiguration::QQuickGraphicsConfiguration(const QQuickGraphicsConfiguration &other)
: d(other.d)
{
d->ref.ref();
}
/*!
\internal
*/
QQuickGraphicsConfiguration &QQuickGraphicsConfiguration::operator=(const QQuickGraphicsConfiguration &other)
{
qAtomicAssign(d, other.d);
return *this;
}
/*!
Destructor.
*/
QQuickGraphicsConfiguration::~QQuickGraphicsConfiguration()
{
if (!d->ref.deref())
delete d;
}
/*!
\return the list of Vulkan instance extensions Qt Quick prefers to
have enabled on the VkInstance.
In most cases Qt Quick is responsible for creating a QVulkanInstance. This
function is not relevant then. On the other hand, when using
QQuickRenderControl in combination with Vulkan-based rendering, it is the
application's responsibility to create a QVulkanInstance and associate it
with the (offscreen) QQuickWindow. In this case, it is expected that the
application queries the list of instance extensions to enable, and passes
them to QVulkanInstance::setExtensions() before calling
QVulkanInstance::create().
\since 6.1
*/
QByteArrayList QQuickGraphicsConfiguration::preferredInstanceExtensions()
{
#if QT_CONFIG(vulkan)
return QRhiVulkanInitParams::preferredInstanceExtensions();
#else
return {};
#endif
}
/*!
Sets the list of additional \a extensions to enable on the graphics device
(such as, the \c VkDevice).
When rendering with a graphics API where the concept is not applicable, \a
extensions will be ignored.
\note The list specifies additional, extra extensions. Qt Quick always
enables extensions that are required by the scene graph.
*/
void QQuickGraphicsConfiguration::setDeviceExtensions(const QByteArrayList &extensions)
{
if (d->deviceExtensions != extensions) {
detach();
d->deviceExtensions = extensions;
}
}
/*!
Sets the usage of depth buffer for 2D content to \a enable. When disabled,
the Qt Quick scene graph never writes into the depth buffer.
By default the value is true, unless the \c{QSG_NO_DEPTH_BUFFER}
environment variable is set.
The default value of true is the most optimal setting for the vast majority
of scenes. Disabling depth buffer usage reduces the efficiency of the scene
graph's batching.
There are cases however, when allowing the 2D content write to the depth
buffer is not ideal. Consider a 3D scene as an "overlay" on top the 2D
scene, rendered via Qt Quick 3D using a \l View3D with
\l{View3D::renderMode}{renderMode} set to \c Overlay. In this case, having
the depth buffer filled by 2D content can cause unexpected results. This is
because the way the 2D scene graph renderer generates and handles depth
values is not necessarily compatible with how a 3D scene works. This may end
up in depth value clashes, collisions, and unexpected depth test
failures. Therefore, the robust approach here is to call this function with
\a enable set to false, and disable depth buffer writes for the 2D content
in the QQuickWindow.
\note This flag is not fully identical to setting the
\c{QSG_NO_DEPTH_BUFFER} environment variable. This flag does not control the
depth-stencil buffers' presence. It is rather relevant for the rendering
pipeline. To force not having depth/stencil attachments at all, set
\c{QSG_NO_DEPTH_BUFFER} and \c{QSG_NO_STENCIL_BUFFER}. Be aware however
that such a QQuickWindow, and any Item layers in it, may then become
incompatible with items, such as View3D with certain operating modes,
because 3D content requires a depth buffer. Calling this function is always
safe, but can mean that resources, such as depth buffers, are created even
though they are not actively used.
*/
void QQuickGraphicsConfiguration::setDepthBufferFor2D(bool enable)
{
if (d->useDepthBufferFor2D != enable) {
detach();
d->useDepthBufferFor2D = enable;
}
}
/*!
\return true if depth buffer usage is enabled for 2D content.
By default the value is true, unless the \c{QSG_NO_DEPTH_BUFFER}
environment variable is set.
*/
bool QQuickGraphicsConfiguration::isDepthBufferEnabledFor2D() const
{
return d->useDepthBufferFor2D;
}
/*!
\return the list of the requested additional device extensions.
*/
QByteArrayList QQuickGraphicsConfiguration::deviceExtensions() const
{
return d->deviceExtensions;
}
QQuickGraphicsConfigurationPrivate::QQuickGraphicsConfigurationPrivate()
: ref(1)
{
static const bool useDepth = qEnvironmentVariableIsEmpty("QSG_NO_DEPTH_BUFFER");
useDepthBufferFor2D = useDepth;
}
QQuickGraphicsConfigurationPrivate::QQuickGraphicsConfigurationPrivate(const QQuickGraphicsConfigurationPrivate *other)
: ref(1),
deviceExtensions(other->deviceExtensions),
useDepthBufferFor2D(other->useDepthBufferFor2D)
{
}
QT_END_NAMESPACE
|