QQuickWindow Class

QQuickWindow uses a scene graph to represent what needs to be rendered. This scene graph is disconnected from the QML scene and potentially lives in another thread, depending on the platform implementation. Since the rendering scene graph lives independently from the QML scene, it can also be completely released without affecting the state of the QML scene.

The sceneGraphInitialized() signal is emitted on the rendering thread before the QML scene is rendered to the screen for the first time. If the rendering scene graph has been released, the signal will be emitted again before the next frame is rendered. A visible, on-screen QQuickWindow is driven internally by a render loop, of which there are multiple implementations provided in the scene graph. For details on the scene graph rendering process, see Qt Quick Scene Graph.

By default, a QQuickWindow renders using an accelerated 3D graphics API, such as OpenGL or Vulkan. See Scene Graph Adaptations for a detailed overview of scene graph backends and the supported graphics APIs.

Integration with Accelerated 3D Graphics APIs▲

Rendering without Acceleration▲

Redirected Rendering▲

Resource Management▲

Exposure and Visibility▲

OpenGL Context and Surface Formats▲

Vulkan Instance▲

Graphics Contexts and Devices▲

See also QQuickView, QQuickRenderControl, QQuickRenderTarget, QQuickGraphicsDevice, QQuickGraphicsConfiguration, QSGRendererInterface

flags QQuickWindow::CreateTextureOptions

The CreateTextureOption enums are used to customize a texture is wrapped.

The CreateTextureOptions type is a typedef for QFlags<CreateTextureOption>. It stores an OR combination of CreateTextureOption values.

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This enum describes the error in a sceneGraphError() signal.

This enum describes the default render type of text-like elements in Qt Quick (Text, TextInput, etc.).

Select NativeTextRendering if you prefer text to look native on the target platform and do not require advanced features such as transformation of the text. Using such features in combination with the NativeTextRendering render type will lend poor and sometimes pixelated results.

This property holds the item which currently has active focus or null if there is no item with active focus.

Access functions:

• *activeFocusItem() const

Notifier signal:

• void activeFocusItemChanged()

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This property holds the color used to clear the color buffer at the beginning of each frame.

By default, the clear color is white.

Access functions:

• color() const

• void setColor(const &color)

Notifier signal:

• void colorChanged(const QColor &)

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This property holds the invisible root item of the scene.

A QQuickWindow always has a single invisible root item containing all of its content. To add items to this window, reparent the items to the contentItem or to an existing item in the scene.

Access functions:

• *contentItem() const

This property holds the window for which this window is a transient pop-up.

This is a hint to the window manager that this window is a dialog or pop-up on behalf of the transient parent, which may be any kind of QWindow.

In order to cause the window to be centered above its transient parent by default, depending on the window manager, it may also be necessary to set the flags property with a suitable Qt::WindowType (such as Qt::Dialog).

Access functions:

• *transientParent() const

• void setTransientParent( *parent)

Notifier signal:

• void transientParentChanged( *transientParent)

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Constructs a window for displaying a QML scene with parent window parent.

Constructs a window for displaying a QML scene, whose rendering will be controlled by the control object. Please refer to QQuickRenderControl's documentation for more information.

Destroys the window.

Returns an accessibility interface for this window, or 0 if such an interface cannot be created.

This signal is emitted on the GUI thread before requesting the render thread to perform the synchronization of the scene graph.

Unlike the other similar signals, this one is emitted on the GUI thread instead of the render thread. It can be used to synchronize external animation systems with the QML content. At the same time this means that this signal is not suitable for triggering graphics operations.

This signal is emitted when the scene graph has submitted a frame. This is emitted after all other related signals, such as afterRendering(). It is the last signal that is emitted by the scene graph rendering thread when rendering a frame.

This function was introduced in Qt 6.0.

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This signal is emitted after the scenegraph has recorded the commands for its main render pass, but the pass is not yet finalized on the command buffer.

This signal is emitted earlier than afterRendering(), and it guarantees that not just the frame but also the recording of the scenegraph's main render pass is still active. This allows inserting commands without having to generate an entire, separate render pass (which would typically clear the attached images). The native graphics objects can be queried via QSGRendererInterface.

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The signal is emitted after scene graph has added its commands to the command buffer, which is not yet submitted to the graphics queue. If desired, the slot function connected to this signal can query native resources, like the command buffer, before via QSGRendererInterface. Note however that the render pass (or passes) are already recorded at this point and it is not possible to add more commands within the scenegraph's pass. Instead, use afterRenderPassRecording() for that. This signal has therefore limited use in Qt 6, unlike in Qt 5. Rather, it is the combination of beforeRendering() and beforeRenderPassRecording(), or beforeRendering() and afterRenderPassRecording(), that is typically used to achieve under- or overlaying of the custom rendering.

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This signal is emitted after the scene graph is synchronized with the QML state.

This signal can be used to do preparation required after calls to QQuickItem::updatePaintNode(), while the GUI thread is still locked.

When using OpenGL, the QOpenGLContext used for rendering by the scene graph will be bound at this point.

This signal is emitted before the scene graph starts preparing the frame. This precedes signals like beforeSynchronizing() or beforeRendering(). It is the earliest signal that is emitted by the scene graph rendering thread when starting to prepare a new frame.

This signal is relevant for lower level graphics frameworks that need to execute certain operations, such as resource cleanup, at a stage where Qt Quick has not initiated the recording of a new frame via the underlying rendering hardware interface APIs.

This function was introduced in Qt 6.0.

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This signal is emitted before the scenegraph starts recording commands for the main render pass. (Layers have their own passes and are fully recorded by the time this signal is emitted.) The render pass is already active on the command buffer when the signal is emitted.

This signal is emitted later than beforeRendering() and it guarantees that not just the frame, but also the recording of the scenegraph's main render pass is active. This allows inserting commands without having to generate an entire, separate render pass (which would typically clear the attached images). The native graphics objects can be queried via QSGRendererInterface.

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This signal is emitted after the preparations for the frame have been done, meaning there is a command buffer in recording mode, where applicable. If desired, the slot function connected to this signal can query native resources like the command before via QSGRendererInterface. Note however that the recording of the main render pass is not yet started at this point and it is not possible to add commands within that pass. Starting a pass means clearing the color, depth, and stencil buffers so it is not possible to achieve an underlay type of rendering by just connecting to this signal. Rather, connect to beforeRenderPassRecording(). However, connecting to this signal is still important if the recording of copy type of commands is desired since those cannot be enqueued within a render pass.

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This signal is emitted before the scene graph is synchronized with the QML state.

Even though the signal is emitted from the scene graph rendering thread, the GUI thread is guaranteed to be blocked, like it is in QQuickItem::updatePaintNode(). Therefore, it is safe to access GUI thread thread data in a slot or lambda that is connected with Qt::DirectConnection.

This signal can be used to do any preparation required before calls to QQuickItem::updatePaintNode().

When using OpenGL, the QOpenGLContext used for rendering by the scene graph will be bound at this point.

When mixing raw graphics (OpenGL, Vulkan, Metal, etc.) commands with scene graph rendering, it is necessary to call this function before recording commands to the command buffer used by the scene graph to render its main render pass. This is to avoid clobbering state.

In practice this function is often called from a slot connected to the beforeRenderPassRecording() or afterRenderPassRecording() signals.

The function does not need to be called when recording commands to the application's own command buffer (such as, a VkCommandBuffer or MTLCommandBuffer + MTLRenderCommandEncoder created and managed by the application, not retrieved from the scene graph). With graphics APIs where no native command buffer concept is exposed (OpenGL, Direct 3D 11), beginExternalCommands() and endExternalCommands() together provide a replacement for the Qt 5 resetOpenGLState() function.

Calling this function and endExternalCommands() is not necessary within the render() implementation of a QSGRenderNode because the scene graph performs the necessary steps implicitly for render nodes.

Native graphics objects (such as, graphics device, command buffer or encoder) are accessible via QSGRendererInterface::getResource().

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Reimplements: QWindow::closeEvent(QCloseEvent *ev).

Creates a simple image node. When the scenegraph is not initialized, the return value is null.

This is cross-backend alternative to constructing a QSGSimpleTextureNode directly.

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Creates a nine patch node. When the scenegraph is not initialized, the return value is null.

Creates a simple rectangle node. When the scenegraph is not initialized, the return value is null.

This is cross-backend alternative to constructing a QSGSimpleRectNode directly.

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Creates a new QSGTexture from the supplied image. If the image has an alpha channel, the corresponding texture will have an alpha channel.

The caller of the function is responsible for deleting the returned texture. The underlying native texture object is then destroyed together with the QSGTexture.

When options contains TextureCanUseAtlas, the engine may put the image into a texture atlas. Textures in an atlas need to rely on QSGTexture::normalizedTextureSubRect() for their geometry and will not support QSGTexture::Repeat. Other values from CreateTextureOption are ignored.

When options contains TextureIsOpaque, the engine will create an RGB texture which returns false for QSGTexture::hasAlphaChannel(). Opaque textures will in most cases be faster to render. When this flag is not set, the texture will have an alpha channel based on the image's format.

When options contains TextureHasMipmaps, the engine will create a texture which can use mipmap filtering. Mipmapped textures can not be in an atlas.

Setting TextureHasAlphaChannel in options serves no purpose for this function since assuming an alpha channel and blending is the default. To opt out, set TextureIsOpaque.

When the scene graph uses OpenGL, the returned texture will be using GL_TEXTURE_2D as texture target and GL_RGBA as internal format. With other graphics APIs, the texture format is typically RGBA8. Reimplement QSGTexture to create textures with different parameters.

This function can be called from both the main and the render thread.

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This is an overloaded function.

Creates a new QSGTexture from the supplied texture.

Use options to customize the texture attributes. Only the TextureHasAlphaChannel flag is taken into account by this function. When set, the resulting QSGTexture is always treated by the scene graph renderer as needing blending. For textures that are fully opaque, not setting the flag can save the cost of performing alpha blending during rendering. The flag has no direct correspondence to the format of the QRhiTexture, i.e. not setting the flag while having a texture format such as the commonly used QRhiTexture::RGBA8 is perfectly normal.

Mipmapping is not controlled by options since texture is already created and has the presence or lack of mipmaps baked in.

The returned QSGTexture owns the QRhiTexture, meaning texture is destroyed together with the returned QSGTexture.

If textur