UnityEngineUIElements

UnityEngineUIElements is a modern UI toolkit for Unity, designed to offer a more flexible and scalable approach to creating user interfaces compared to the legacy Unity UI (UGUI) system. It leverages a declarative UXML markup language, similar to HTML, for structuring UI layouts, and USS stylesheets, akin to CSS, for styling. This separation of structure and presentation allows for easier maintenance and customization.

The system is built around the concept of elements, which are the fundamental building blocks of the UI. These elements can be simple like buttons or labels, or more complex, combining multiple other elements into reusable components. UXML files define the hierarchy and properties of these elements, while USS files control their appearance, such as color, size, and positioning.

A key advantage of UI Toolkit is its performance, especially for complex UIs. It utilizes a retained mode rendering system that can be more efficient than UGUI's immediate mode rendering. Furthermore, it integrates well with C# scripting, allowing developers to dynamically create, manipulate, and bind data to UI elements. The system also supports features like responsive design, enabling UIs to adapt to different screen sizes and resolutions. UI Toolkit is increasingly becoming the recommended solution for new UI development in Unity.