Qt Framework and QML

Qt-framework-and-QML-overview

Frameworks play in favor of effective app development because of out-of-the-box constituents. Their aim is to help standardize the software development process, making it quicker and easier. Qt framework is a popular solution for GUI development. In this article, we will examine the benefits of Qt and QML implementation in the IT industry.

What Is QT?

Qt is a C++framework for developing graphical user interfaces and cross-platform applications, both desktop and embedded. The framework can function on different types of software and hardware. Initially, it was created as a class library, and over the years the license underwent numerous transformations. Users can choose between two available types of license: a commercial paid license and a free open source license.

It offers a special software development language: Qt Modeling Language(QML), which is widely implemented in projects to create user interface–focused apps. In addition, it can be bound with other languages such as:

  • Java
  • Python
  • Go
  • PHP
  • Ruby
  • Ring
  • Zig
  • Crystal
  • Rust
  • R, etc.

The Qt Integrated Development Environment (IDE) is known as Qt Creator. To add extra features to Qt, developers often use addon modules in their projects. These can either work with specific platforms only, or are backward-compatible. Some addons are available only in the commercial license. In the free license, there are no such options.

Thanks to the widget toolkit, programmers can code straightaway in C++. Qt Designer can generate code for widget-based graphical user interface software in interactive mode. A special instrument called the Qt Quick module streamlines GUI development with the help of QML.

As of today, there are 4 editions on the market:

  • Community
  • Indie Mobile
  • Professional
  • Enterprise

Software engineers can use the basic version available under a free license. To access more features they have to buy the more advanced versions under the commercial license from Qt Company.

Qt Components

The backbone of the framework is formed by Qt Essentials modules. They are the following:

Qt Essentials ModulesFeatures
Qt CoreThese non-graphic core classes were not required by all other modules
Qt GUIBasic classes used for GUI design, including OpenGL
Qt MultimediaA set of QML types and C++ classes to process multimedia
Qt Multimedia WidgetsClasses based on widgets to implement multimedia features
Qt NetworkAPIs for apps rely on TCP/IP networks
Qt QMLFramework and types of Qt QML markup language
Qt QuickFramework to create dynamic apps with custom QML UI
Qt Quick Controls 2Lightweight, very efficient QML types that simplify the interface formulation
Qt Quick DialogsTypes for creation and interaction with system dialogs
Qt Quick LayoutsQML types for the layout of objects in the developed interface
Qt Quick TestTest framework for QML apps
Qt SQLClasses for SQL databases integration
Qt TestClasses for detailed tests of Qt applications and libraries
Qt WidgetsSet of UI elements for classic UI creation

9 Reasons to Choose Qt

Adavntages-of-Qt

The multi-platform framework offers huge advantages in software development:

  • With Qt, you can create code that is easy to read, reuse and maintain, which occupies less space and has proven high-quality performance.
  • You’ll have the ability to create cutting-edge appealing Qt GUI.
  • Due to its highly productive features, Qt software development takes less time and remains a cost-effective solution.
  • Because of C++ programming language implementation, programmers can use manifold libraries.
  • APIs make Qt app development easier.
  • The framework has cross-platform characteristics.
  • It’s easier to create 3D graphical user interfaces with the help of 3D Studio.
  • As a result, your software will have a graphical user interface similar to a native one.
  • The wide choice of modules allows rich functionality in a project.

Programming with Qt

These are the concepts that the framework foundation is based on:

  • Graphical User Interface Abstraction

The latest versions leverage native-style API of the platform. This helps avoid the problems that Qt had earlier. Previously it implemented its own paint engine and controls and emulated the platform, which led to inconsistencies when the emulating process was not perfect.

  • Signals and Slots

A GUI widget sends signals that contain event data. Subsequently, the controls together with slots catch the signals.

  • Language Bindings

Language bindings allow programmers the usage of other programming languages during the project.

QML (Qt Markup Language)

QML is a programming and user interface specification language. The existing functionality of this language can be enriched through the implementation of C++.

QML Usage

Software developers can build high-performance apps rich in visual characteristics and animation with Qt Markup Language. It was created to dynamically interconnect the constituent elements that the developers can reuse and customize afterward. Programmers appreciate the ability to create GUI with dynamic effects and smooth transitions, which is especially beneficial for building mobile apps. QML can be of use in 3D scene description, touch input, and UX enhancement.

Features

  • Anchors

Besides usual layouts, items possess seven concealed anchor lines (left, horizontal, center, right, top, vertical center, baseline, bottom)

  • MouseArea

Concealed item used for mouse handling

  • Property Bindings

Help in specifying relations among various object properties

  • DragHandler

Moves the items in an interactive mode

  • State

An item possesses a default state, which changes after the configuration is changed

  • Animation

Programmers create animation by introducing an animation element to a property value

  • Transition

When the state changes, the transitions are animated

  • Behavior

Shows typical animation in case of property value alterations

  • Dynamic Load of Components

The loader element can dynamically load Qt markup language components

  • Event System

The event system allows responding to a signal through the help of a handler

Syntax

QML is a declarative language with syntax analogous to CSS and JSON that supports imperative JS expressions. QML defines the attributes of objects and their relations and responses to other objects’ changes. Unlike imperative languages, it integrates changes in attributes, as well as behavior straight into the object definition. As a rule, an engine loads the source code of the Qt markup language from QML documents. Developers can then reuse object types further in the application.

Performance

  • Implements the graphics processing unit to accelerate the calculation process
  • Is written in C++ and functions natively on each supported platform
  • Has C++ components
  • The majority of QML apps include large chunks of JS
  • Uses JIT and AOT compilation
  • Apps in QML are developed with a focus on native technologies of the platforms

Qt Platforms

You can create graphical user interfaces for deployment on desktop, mobile, and embedded OS. There will be no need to rewrite the source code. To use Qt for a 32- or 64-bit platform, all you need is the right compiler and renderer.

Below you can find the supported platforms:

  • Desktop platforms:
    • Linux/X11
    • macOS
    • Windows
  • Mobile platforms:
    • Android
    • iOS/tvOS/watchOS
    • Universal Windows Platform (UWP)
    • Qt for WebAssembly
  • Embedded platforms (with Qt for Device Creation):
    • Linux
    • QNX
    • INTEGRITY
    • VxWorks

Where Is Qt Used

Qt is a popular solution used in projects that are focused on creating embedded devices and Internet-of-Things software. It is also used for desktop and mobile development. One of the best-known Qt projects is KDE Plasma, which is often ranked as the best desktop environment. Qt is used by such companies as LG, Tesla, Microsoft, Samsung, BMW, Siemens, HP, Philips, etc.

Below you will find other examples of Qt-based software.

Examples-of-Qt-software

Conclusion

Qt is a powerful time-saving solution for GUI and app creation, especially when it is necessary to combine the efforts of UI/UX and development teams. The QML programming language is often associated with Qt development.

Qt can be used for desktop, embedded, and mobile development on multiple platforms. You can choose either a free or commercial license based on your specific needs. If you work on a complex high-load project, we recommend you use a commercial license.

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About the author

Maryia Shapel
Maryia Shapel

As a content writer, Maryia strives to create enlightening blog posts and technical articles based on the latest technology trends and established best practices. Her aim is to tell more about SaM Solutions and promote the company’s expertise.

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  • Thank you for explaining the advantages of Qt and QML. I am thinking about learning and using it on a daily basis for the development of graphical user interface.

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