Changes to Qt Quick
Qt 6 是努力使框架更高效，且更易于使用的结果。
为兼容每个发行的所有公共 API，我们试着维护二进制和源代码。但是，为使 Qt 成为更优框架，一些改变是不可避免的。
In this topic we summarize those changes in Qt Quick, and provide guidance to handle them.
Changes to Qt Quick QML Types
Changed Type of font.weight
The type of
font.weight
has been changed to
int
. The pre-defined weight classes still exist, but it is now possible to use arbitrary integers to select fonts which do not match any of these weight classes. This ensures parity with the C++ API, where it has always been possible to express the font weight as an arbitrary integer.
Most code will be unaffected by this change, except in the case where an implicit conversion from a string to enum value was used.
font.weight: "Bold"
This code will no longer parse correctly and has to be replaced by its equivalent enum value, as demonstrated below.
font.weight: Font.Bold
FontLoader.name Is Now a Read-Only Property
In Qt 5, the
name
property of
FontLoader
was writable and would override the source property of the item when set. This caused some confusion as to its purpose and could cause undeterministic behavior if there was a race condition between the setters for the conflicting properties.
This means that code such as the following will no longer work.
FontLoader {
id: fontLoader
name: "Helvetica"
}
Text {
font.family: fontLoader.name
text: "Foobar"
}
Instead, use a custom property to store font family names.
property string fontName: "Helvetica"
Text {
font.family: fontName
text: "Foobar"
}
The OpenGLInfo QML Type Is Removed
In Qt 5.8, OpenGLInfo was deprecated and is removed for Qt 6. Please use
GraphicsInfo
代替。
ShaderEffect No Longer Supports Inline GLSL Shader Strings
Just like with
custom materials
, the effects are no longer specified in form of GLSL shader strings. Rather, shaders are expected to be preprocessed by the tools from the
Qt Shader Tools
module, such as the
qsb
command line tool, thus ensuring the shader assets are usable regardless of which graphics API (Vulkan, Metal, OpenGL, or Direct 3D) is used at runtime.
ShaderEffect
items are expected to reference the resulting
.qsb
文件。
ShaderEffect Source Properties Are Now URLs
The
ShaderEffect
properties
vertexShader
and
fragmentShader
both have a type of
QUrl
now, instead of
QByteArray
. Their behavior is therefore identical to other similar properties, such as
Image.source
. Existing code that refers to files via the
file
or
qrc
scheme will continue to work as-is. In addition, this change allows referring to files with a path relative to the component's (the .qml file's) location. Specifying the
file:
scheme is therefore optional now.
Changes to Qt Quick C++ APIs
Changes to QQuickItem
QQuickItem
's geometryChanged() function was renamed to
geometryChange
().
Changes to QQuick* APIs
-
Applications wishing to integrate their own set of Vulkan, Metal, or Direct3D rendering commands should be aware of new
QQuickWindow
signals in addition to
QQuickWindow::beforeRendering
() and afterRendering(). The existing Qt 5 pattern of connecting to just beforeRendering or afterRendering is often not sufficient anymore on its own, and will likely need to be complemented by connecting to additional signals, such as
beforeRenderPassRecording
() 或
afterRenderPassRecording
().
-
Applications that rely on the
QQuickWindow::beforeRendering
() or afterRendering() signals to issue their own set of OpenGL rendering commands should call
QQuickWindow::beginExternalCommands
() before, and
QQuickWindow::endExternalCommands
() after, the OpenGL calls. This ensures that state changes made by the application code does not lead to confusion with regards to the scene graph renderer's own cached state. Note however, that, just like in Qt 5, changing OpenGL 3.x or 4.x state that is not used by the Qt Quick renderer can still lead to unexpected issues, so therefore application are advised to reset any such OpenGL state to the default value before returning from the slots or lambdas connected to these signals.
-
The existing
QQuickWindow::setRenderTarget
() overloads, and the related getters, are removed and replaced by a new function taking a
QQuickRenderTarget
. Applications performing redirected rendering in combination with
QQuickRenderControl
are now expected to use this new function to specify the render target in a manner that is not tied to OpenGL.
-
The
QQuickWindow::setSceneGraphBackend
() overload taking a
QSGRendererInterface::GraphicsApi
argument has been renamed to
setGraphicsApi
().
-
The
QQuickWindow
functions setPersistentOpenGLContext and isPersistentOpenGLContext are renamed, and are now
QQuickWindow::setPersistentGraphics
() 和
QQuickWindow::isPersistentGraphics
().
-
setClearBeforeRendering() and clearBeforeRendering() have been removed from
QQuickWindow
. There is no option for skipping the color buffer clearing in Qt 6. Calling setClearBeforeRendering() was often necessary in Qt 5 in combination with underlays, to prevent Qt Quick from clearing the content rendered into the color buffer. In Qt 6, there is a more robust approach: connecting to the
beforeRenderPassRecording()
signal, that is emitted after clearing, but before rendering Qt Quick's content.
-
The QQuickWindow::openglContext() function has been removed. When the application has ensured the scene graph is using OpenGL for rendering, it can query the
QOpenGLContext
from
QSGRendererInterface::getResource
().
-
The QQuickWindow::openglContextCreated() signal has been removed.
-
The deprecated QQuickWindow::createTextureFromId() function has been removed. Instead, use the fromNative() function from QPlatformInterface::QSGOpenGLTexture, QPlatformInterface::QSGVulkanTexture, QPlatformInterface::QSGD3D11Texture, or QPlatformInterface::QSGMetalTexture.
-
The
QQuickFramebufferObject
class is available with an unchanged API, but is only functional when the scenegraph is rendering with OpenGL. It will not be functional when using another graphics API, such as Vulkan or Metal. Applications relying on
QQuickFramebufferObject
should force the usage of OpenGL by calling
QQuickWindow::setGraphicsApi(QSGRendererInterface::OpenGL)
in their main() function.
-
QQuickRenderControl
has a slightly changed API: grab() is now removed, use
QQuickWindow::grabWindow
() instead, where applicable. The initialize() function no longer takes a
QOpenGLContext
. Applications are now also required to call
QQuickRenderControl::beginFrame
() 和
QQuickRenderControl::endFrame
() as appropriate. When multisampling is desired, the new function
QQuickRenderControl::setSamples
() must be called to indicate the sample count.
-
Applications wishing to perform Qt Quick rendering in combination with an existing native graphics device or context object must take the new
QQuickWindow::setGraphicsDevice
() function into use as
QQuickRenderControl
no longer provides the
initialize(QOpenGLContext*)
函数。
-
设置
QQuickPaintedItem
and
Context2D
to
Framebuffer
mode has no effect. It will behave as if the mode was set to the default Image mode.
-
环境变量
QSG_NO_DEPTH_BUFFER
is still supported in Qt 6.0, but its usage is recommended to be replaced by calling
setDepthBufferFor2D
() 在
QQuickGraphicsConfiguration
that is then associated with the
QQuickWindow
.
Changes to QSG* APIs
-
QSGMaterialShader
has a changed interface. Implementations should not rely on OpenGL anymore, and cannot assume that functions, such as the now-removed updateState(), are called with a
QOpenGLContext
current. In the new, data-oriented interface updateState() is replaced by
updateUniformData
(),
updateSampledImage
()，和
updateGraphicsPipelineState
(). Instead of GLSL shader code provided as strings, shaders are now expected to be preprocessed by the tools from the Qt Shader Tools module, such as the
qsb
command line tool, thus ensuring the shader assets are usable regardless of which graphics API (Vulkan, Metal, OpenGL, or Direct 3D) is used at run time.
-
QSGEngine has been removed. In the unlikely case of an application utilizing this class, it is recommended to port to using
QQuickRenderControl
代替。
-
QSGAbstractRenderer is no longer public. The usage of this class made sense only in combination with QSGEngine, and with that class being removed QSGAbstractRenderer has been moved back to private.
-
The QSGSimpleMaterial convenience class has been removed. Applications are expected to use the revised, OpenGL-independent
QSGMaterial
APIs instead.
-
To access the underlying native texture object for a
QSGTexture
, textureId() is no longer available. Instead, use QSGTexture::platformInterface() with QPlatformInterface::QSGOpenGLTexture, QPlatformInterface::QSGVulkanTexture, QPlatformInterface::QSGD3D11Texture, or QPlatformInterface::QSGMetalTexture.
-
子类化的
QSGImageNode
are now required to override new additional virtuals, such as setAnisotropyLevel() and anisotropyLevel().
-
子类化的
QSGTexture
will likely need to be redesigned. Some of the OpenGL-specific virtual functions, such as bind() or updateBindOptions(), are no longer present, while there are new virtuals that are mandatory to implement, such as
comparisonKey
().
Changes to OpenGL Use in Qt Quick
While it will present no breaks for many applications, application developers should be aware that, OpenGL is not always the default choice anymore for Qt Quick rendering in Qt 6. Unless the
software
backend is used, a Qt Quick application could use OpenGL, Vulkan, Metal, or Direct3D 11 at runtime. When no explicit request is made, either via the
QSG_RHI_BACKEND
environment variable or the
QQuickWindow::setSceneGraphBackend
() function, a platform-specific default is chosen by Qt Quick.
更多信息，拜访
Qt Quick 场景图形
和
Qt Quick 场景图形默认渲染器
页面。
