User Interfaces

Qt features multiple technologies for creating user interfaces. While it is possible to mix and match these different technologies as needed, one approach is often better suitable for a certain type of user interface than the others. Qt Creator is a good example of an application that mixes different user interface technologies. In fact, it uses all of the three different approaches described below. Qt Creator uses the traditional Qt Widgets such as menus and dialogs as a basis of the user interface, Qt Quick amongst others for the welcome screen, and Qt WebKit for presenting the Qt reference documentation. The following sections provide brief introductions to the available technologies for creating user interfaces, and a comparison table to help choosing the best suitable technology.

QML Graphical User Interfaces

QML allows developers to build user interfaces in a declarative way. User interfaces specifically benefit from the simplicity of compounding QML objects and configuring them using property bindings.

Qt Quick is a module which supplies QML types for creating user interfaces such as a visual canvas with its own coordinate system and rendering engine. Animation and transition effects are a first class concept in Qt Quick and visual effects can be supplemented through specialized components for particle and shader effects.

Important UI Topics for QML Applications

Graphical Controls

The Qt Quick Controls module is new in Qt 5.1 and provides a set of UI elements to create user interfaces using Qt Quick 2.

For more about how to create application user interfaces with QML, visit the QML User Interfaces page.

Qt Widgets

Qt Widgets are traditional user interface elements that are typically found in desktop environments. The widgets integrate well to the underlying platform providing native look'n'feel on Windows, Linux and Mac OSX. The widgets are mature and feature rich user interface elements suitable for mostly static user interfaces. In contrast to Qt Quick, the widgets do not scale that well for touch screens and fluid, highly animated modern user interfaces. The widgets are a good choice for applications with traditional desktop centric user interfaces, such as office type applications.

Important Concepts in Qt Widgets

Displaying Web Content

Qt provides a WebKit-based layout engine with support for a wide range of standard web techologies such as HTML, CSS and JavaScript, that make it possible to embed content from the World Wide Web into your Qt application. Qt features both WebKit-based QML and C++ APIs.

Qt WebKit displays web content through the WebView QML type while the Qt WebKit Widgets features a C++ API to render and interact with web content.

The main difference between the two APIs is that WebView utilizes a multi- process architecture, WebKit2, with a separate web rendering process. The C++ API uses the previous version of WebKit, which has a single-process architecture.

See also Integrating Web Content.

Comparison

Notice that choosing the appropriate technology for building an user interface is not always black and white, but may depend on several criterias, such as other existing technologies used in a project or even target platform constraints. To some extent, many items in the following table can be implemented using any of the three available technologies. The following table merely aims to help you choose the best suited tool for the job.

Qt Quick / Qt Quick ControlsQt WidgetsQt WebKitComments
Used language(s)QML/JSC++HTML/CSS/JS
Native look'n'feelXXQt Widgets and Qt Quick Controls integrate well to the underlying platform, providing a native look'n'feel on Windows, Linux, and Mac OS X.
Custom look'n'feelX(X)Qt Widgets provide means for customization via style sheets, but Qt Quick is a better performing choice for user interfaces that do not aim to look native.
Fluid animated UIsXQt Widgets do not scale well for animations, and Qt WebKit's CSS3 animations are not as powerful as Qt Quick animations. Qt Quick offers a convenient and natural way to implement animations in a declarative manner.
Touch screenXQt Widgets often require a mouse cursor for good interaction, whereas Qt Quick only provides primitive building blocks that were designed with touch interaction in mind. The WebView Qt Quick component has support for multi-touch gestures to interact with web content.
Standard industry widgetsXQt Widgets provide all the bells and whistles, developed over two decades, needed for building standard industry type applications. Qt WebKit Widgets provide widgets and additional classes to render and interact with web content.
Model/View programming(X)XSome MVC like concepts exist in Qt WebKit, Qt Quick provides convenient views, but Qt Widgets provide more convenient and complete frameworks. In addition to Qt Quick views, Qt Quick Controls provide a TableView.
Rapid UI developmentX(X)Thanks to its superior productivity, Qt Quick is an excellent choice for rapid UI prototyping and development.
HW accelerated graphicsXQt Widgets provide QGLWidget for rendering OpenGL graphics, and Qt WebKit supports WebGL, but the OpenGL ES 2.0 or OpenGL 2.0 based Qt Quick Scene Graph has proven to provide the best performance for UIs and for integrating with OpenGL content.
Graphical effectsXThe particle system and shader effects available in Qt Quick are more flexible compared to CSS Effects and Shaders available in Qt WebKit. Qt Widgets offer very little in this area.
Rich text processingXXQt Widgets currently provide the most comprehensive base for implementing text editors. Qt's rich text document classes can also be utilized in Qt Quick and Qt Quick Controls' TextArea, but may require some C++ implementation.
Existing web contentXBoth Qt Quick and Qt Widgets prodive components for presenting simple rich text, but Qt WebKit is the right choice for presenting full-blown web content.

Internationalization and Translations

Qt provides excellent support for translating applications into local languages. Release managers, translators, and developers can use Qt translation tools to accomplish their tasks.

Notes provided by the Qt Community

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