Guillaume is a flexible, lightweight UI library for building user interfaces on XR and traditional platforms. Its design emphasizes a small footprint, predictable performance, and clean integration with custom rendering and input stacks.

Programming Language

Guillaume is implemented in modern C++ (targeting C++20) to balance performance with safety and clarity. This enables:

• Low-latency code paths and deterministic memory control where needed.
• Broad portability and easy interop with existing engines and native toolchains.
• Use of modern language features to improve maintainability without sacrificing performance.

Why not use an existing UI library?

Mature UI frameworks (for example, Qt or React Native) were evaluated. They commonly:

• Assume control over rendering and input pipelines, which conflicts with XR engines and custom renderers.
• Constrain frame scheduling and threading models, making XR latency budgets harder to meet.
• Optimize for 2D application UIs rather than spatial layouts, custom hit-testing, or XR interaction models.
• Make deep integration with domain-specific asset and scene pipelines more complex.

Additionally, they can be heavyweight and may not provide the flexibility needed for custom rendering systems.

Script Language

Like QT with QML or Reat with JSX, Guillaume uses a declarative approach to define user interfaces. For this purpose, the library will use a script language to describe the UI structure and behavior.

The choice of script language is still under consideration, with options including Python and Lua.

Rendering

Guillaume is designed to be rendering-agnostic, allowing developers to integrate it with their custom rendering systems.

This flexibility enables the library to be used across different platforms and rendering technologies.

Input Handling

Guillaume does not impose any specific input handling mechanism. Instead, it provides a flexible interface for developers to integrate their own input handling systems.

This approach ensures that the library can be adapted to various input devices and interaction paradigms.