setContent(url, component, item)
This is a convenience wrapper for
QQuickWindow which will automatically load and display a QML scene when given the URL of the main source file. Alternatively, you can instantiate your own objects using
QQmlComponent and place them in a manually set up
QQuickWidget *view = new QQuickWidget; view->setSource(QUrl::fromLocalFile("myqmlfile.qml")); view->show();
QQuickWidget also manages sizing of the view and root object. By default, the
SizeViewToRootObject , which will load the component and resize it to the size of the view. Alternatively the
resizeMode may be set to
SizeRootObjectToView which will resize the view to the size of the root object.
QQuickWidget is an alternative to using
QQuickView and . The restrictions on stacking order do not apply, making
QQuickWidget the more flexible alternative, behaving more like an ordinary widget. This comes at the expense of performance. Unlike
QQuickWidget involves rendering into OpenGL framebuffer objects. This will naturally carry a minor performance hit.
QQuickWidget disables the threaded render loop on all platforms. This means that some of the benefits of threaded rendering, for example Animator classes and vsync driven animations, will not be available.
Avoid calling on a
QQuickWidget . This function triggers the creation of a native window, resulting in reduced performance and possibly rendering glitches. The entire purpose of
QQuickWidget is to render Quick scenes without a separate native window, hence making it a native widget should always be avoided.
Scene Graph and Context Persistency¶
isPersistentSceneGraph() , meaning that applications can decide - by calling
setPersistentSceneGraph() on the window returned from the
quickWindow() function - to let scenegraph nodes and other Qt Quick scene related resources be released whenever the widget becomes hidden. By default persistency is enabled, just like with
When running with the OpenGL backend of the scene graph,
QQuickWindow offers the possibility to disable persistent OpenGL contexts as well. This setting is currently ignored by
QQuickWidget and the context is always persistent. The OpenGL context is thus not destroyed when hiding the widget. The context is destroyed only when the widget is destroyed or when the widget gets reparented into another top-level widget’s child hierarchy. However, some applications, in particular those that have their own graphics resources due to performing custom OpenGL rendering in the Qt Quick scene, may wish to disable the latter since they may not be prepared to handle the loss of the context when moving a
QQuickWidget into another window. Such applications can set the QCoreApplication::AA_ShareOpenGLContexts attribute. For a discussion on the details of resource initialization and cleanup, refer to the
QQuickWidget offers less fine-grained control over its internal OpenGL context than
QOpenGLWidget , and there are subtle differences, most notably that disabling the persistent scene graph will lead to destroying the context on a window change regardless of the presence of QCoreApplication::AA_ShareOpenGLContexts.
Putting other widgets underneath and making the
QQuickWidget transparent will not lead to the expected results: the widgets underneath will not be visible. This is because in practice the
QQuickWidget is drawn before all other regular, non-OpenGL widgets, and so see-through types of solutions are not feasible. Other type of layouts, like having widgets on top of the
QQuickWidget , will function as expected.
When absolutely necessary, this limitation can be overcome by setting the
WA_AlwaysStackOnTop attribute on the
QQuickWidget . Be aware, however that this breaks stacking order. For example it will not be possible to have other widgets on top of the
QQuickWidget , so it should only be used in situations where a semi-transparent
QQuickWidget with other widgets visible underneath is required.
This limitation only applies when there are other widgets underneath the
QQuickWidget inside the same window. Making the window semi-transparent, with other applications and the desktop visible in the background, is done in the traditional way: Set
WA_TranslucentBackground on the top-level window, request an alpha channel, and change the Qt Quick Scenegraph’s clear color to
Support when not using OpenGL¶
In addition to OpenGL, the
software backend of Qt Quick also supports
QQuickWidget . Other backends, for example OpenVG , are not compatible however and attempting to construct a
QQuickWidget will lead to problems.
Tab Key Handling¶
On press of the
[TAB] key, the item inside the
QQuickWidget gets focus. If this item can handle
[TAB] key press, focus will change accordingly within the item, otherwise the next widget in the focus chain gets focus.
Exposing Attributes of C++ Types to QML Qt Quick Widgets Example
QQuickWidget with the given QML
Note: In this case, the
QQuickWidget does not own the given
engine object; it is the caller’s responsibility to destroy the engine. If the
engine is deleted before the view,
status() will return
QQuickWidget with the given
parent. The default value of
parent is 0.
This enum specifies how to resize the view.
The view resizes with the root item in the QML.
The view will automatically resize the root item to the size of the view.
Specifies the loading status of the
QQuickWidgethas no source set.
QQuickWidgethas loaded and created the QML component.
QQuickWidgetis loading network data.
One or more errors occurred. Call
errors()to retrieve a list of errors.
Returns a pointer to the
QQmlEngine used for instantiating QML Components.
- Return type
Return the list of errors that occurred during the last compile or create operation. When the status is not
Error , an empty list is returned.
Returns the actual surface format.
If the widget has not yet been shown, the requested format is returned.
Renders a frame and reads it back into an image.
This is a potentially expensive operation.
Returns the initial size of the root object.
SizeRootObjectToView , the root object will be resized to the size of the view. This function returns the size of the root object before it was resized.
Returns the offscreen
QQuickWindow which is used by this widget to drive the Qt Quick rendering. This is useful if you want to use
QQuickWindow APIs that are not currently exposed by
QQuickWidget , for instance connecting to the
beforeRendering() signal in order to draw native OpenGL content below Qt Quick’s own rendering.
Use the return value of this function with caution. In particular, do not ever attempt to show the
QQuickWindow , and be very careful when using other
QWindow -only APIs.
The offscreen window may be deleted (and recreated) during the life time of the
QQuickWidget , particularly when the widget is moved to another
QQuickWindow . If you need to know when the window has been replaced, connect to its
This function returns the root of the context hierarchy. Each QML component is instantiated in a
QQmlContext ‘s are essential for passing data to QML components. In QML, contexts are arranged hierarchically and this hierarchy is managed by the
Returns the view’s root
item . Can be null when
setSource() has not been called, if it was called with broken QtQuick code or while the QtQuick contents are being created.
message – str
This signal is emitted when an
error occurred during scene graph initialization.
Applications should connect to this signal if they wish to handle errors, like OpenGL context creation failures, in a custom way. When no slot is connected to the signal, the behavior will be different: Quick will print the
message, or show a message box, and terminate the application.
This signal will be emitted from the GUI thread.
Sets the clear
color. By default this is an opaque color.
To get a semi-transparent
QQuickWidget , call this function with
color set to
transparent , set the
WA_TranslucentBackground widget attribute on the top-level window, and request an alpha channel via
setContent(url, component, item)¶
Sets the source
component and content
item (root of the QML object hierarchy) directly.
Sets the surface
format for the context and offscreen surface used by this widget.
Call this function when there is a need to request a context for a given OpenGL version or profile. The sizes for depth, stencil and alpha buffers are taken care of automatically and there is no need to request those explicitly.
Sets the source to the
url, loads the QML component and instantiates it.
Ensure that the URL provided is full and correct, in particular, use
fromLocalFile() when loading a file from the local filesystem.
Calling this method multiple times with the same URL will result in the QML component being reinstantiated.
Returns the source URL, if set.
This signal is emitted when the component’s current
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