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Adi2 brings CSS styling and XML layouts to native Ada GUIs

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Adi2 brings CSS styling and XML layouts to native Ada GUIs

Aldo Nicolas Bruno released Adi2, a GUI widget toolkit written natively in Ada and built on top of SDL3. The pitch is that Ada developers get the conveniences common in modern UI stacks but rarely available in the language: CSS-like styling with live reload during development, declarative XML for UI layouts, animations, SVG and Lottie graphics, internationalization through Gettext-compatible i18n, and single-binary asset bundling. Interfaces can be styled with actual CSS syntax (selectors, pseudo-classes, transitions, gradients, box shadows) that hot-reloads on save, or the same style rules can be written as plain Ada aggregates for developers who prefer not to touch a separate file format. UI trees can likewise be described in XML, which the toolchain compiles into typed Ada packages, or built directly in Ada using handle-based widget constructors; both approaches produce the same underlying API, so XML is a convenience rather than a requirement. A release build links everything statically, widget toolkit, CSS engine, SVG and Lottie rendering, into a single executable under 10 MB before the app's own code and assets are added. Rendering goes through SDL3, which maps to whatever graphics backend the host provides: Direct3D on Windows (including Direct3D 9 on Windows XP), Metal on macOS, Vulkan or OpenGL elsewhere, and software rendering as a fallback. The project says it is tested on GNU/Linux, Windows XP through 11 (via MinGW), macOS, and WebAssembly via Emscripten, with the same source producing working binaries across that whole range. A built-in, development-only MCP bridge lets editors and AI assistants screenshot the running app, inspect the widget tree, and drive it directly, clicking buttons, typing into fields, moving focus, reading performance counters, which the author frames as useful for end-to-end tests written by an AI assistant. The README lists the status as already in production use, but not yet a stable release, warning that APIs may still change between versions. It is licensed under Apache-2.0, and the author presented the project at the 3rd Ada Developers Workshop at AEiC 2026 on 13 June 2026. A roadmap lists further work without dates or version targets: a broader CSS property surface, HTML table and flexbox/grid support inside the built-in HTML view widget, more widgets (tree view, data grid, menu bar, date and colour pickers), ready-made Material, Fluent, Adwaita and macOS themes, right-to-left and bidirectional text, accessibility support over AT-SPI, UI Automation and NSAccessibility, pluggable rendering backends beyond SDL3, a visual designer, and a stable C API for non-Ada callers. The project is independently developed and maintained; the author invites sponsorship or paid feature/port work through a listed contact address, while noting that sponsorship supports the project generally and does not by itself carry guaranteed response times or delivery commitments.

Key facts

  • Aldo Nicolas Bruno built Adi2, a native Ada GUI toolkit on top of SDL3 with CSS-like styling, live reload, and declarative XML layouts.
  • A statically linked release build, including the widget toolkit, CSS engine, and SVG/Lottie rendering, comes in under 10 MB before app-specific code and assets.
  • The toolkit targets GNU/Linux, Windows XP through 11, macOS, and WebAssembly from the same source, rendering through whichever backend SDL3 exposes on each platform (Direct3D, Metal, Vulkan, OpenGL, or software).
  • A development-only MCP bridge lets editors and AI assistants screenshot the running app, walk its widget tree, and drive it for automated end-to-end testing.
  • The README marks Adi2 as already in production use but not yet a stable release, with APIs still subject to change; it is licensed under Apache-2.0.

Why it matters

Ada is a language best known for safety-critical and embedded systems work, and it has historically lacked the kind of modern, styleable UI tooling that web and mobile developers take for granted. Adi2 imports patterns from the web world, CSS syntax, hot reload, declarative markup, into a native Ada toolkit built directly on SDL3 rather than wrapping an existing cross-platform UI framework. The result is a single statically linked binary under 10 MB that still supports gradients, transitions, and box shadows, which is a distinctive combination for a systems-level language.

Who it affects

The toolkit is aimed at Ada developers building desktop or embedded GUI applications who want a modern styling and layout workflow without leaving the language, including on older or unusual targets such as Windows XP. Its MCP bridge also targets developers building AI-assisted or AI-driven test automation, since it lets an assistant inspect and operate the running UI directly. The project's reach is inherently narrow: Ada's developer base is small relative to mainstream application languages.

How to use it

Adi2 is distributed under the Apache-2.0 license, with contributions understood to fall under the same license unless stated otherwise and no contributor agreement to sign. It builds through Alire (alr build) and ships example programs in both the XML/CSS pipeline and pure hand-written Ada, with a roughly 25-line example program shown for the minimal case. Its public APIs use Ada 2022 constructs, so consuming code needs pragma Ada_2022 or the -gnat2022 compiler flag. Organisations wanting a specific feature, port, or integration, or a commercial support arrangement with guaranteed response times, are directed to contact the project by email rather than relying on general sponsorship alone.

How solid is it

The project's own status line describes Adi2 as already in production use, while explicitly cautioning that it is not yet a stable release and that APIs may still change between versions. The author reports testing across GNU/Linux, Windows XP through 11 (via MinGW), macOS, and WebAssembly through Emscripten, and says any platform where GNAT and SDL3 build, including the BSDs, should work as well, though that broader claim is not independently verified in the source. The project was presented at the 3rd Ada Developers Workshop at AEiC 2026 on 13 June 2026. It is described as independently developed and maintained by its single named author, with no information given on team size, contributor count, or how long the project has existed.

Risks and caveats

Adopters are taking on pre-1.0 software by the project's own description: an API that may still change, and a roadmap, broader CSS coverage, more widgets, accessibility support, a visual designer, a stable C API, that is listed as planned rather than scheduled, with no version numbers or dates attached to any of it. The source gives no benchmark or performance comparison against established GUI toolkits, and no figures on downloads, contributors, or existing deployments beyond the author's own description of production use. As a project maintained by one named individual, its longevity depends on that person's continued involvement unless further contributors or sponsors join.