gbui 0.2

The first version with a published site, a CI pipeline, an installable library
and a set of application screens to look at. It is the version the documentation
described from the start; it had never been tagged, which is what this tag fixes
— an archived version with no tag is a dropdown entry that 404s.

The toolkit

• Build → layout → paint, three stages in one direction: layout is
  arithmetic that can be asserted without a window, and painting is a display
  list that can be inspected without a GPU.
• CSS flexbox with wrapping, percentages, min-content sizing and out-of-flow
  positioning, in logical pixels — a 200% display is a property of the output
  rather than something a component knows about.
• Theming as data: 24 semantic tokens read from the gitbox-themes
  registry's JSON, with Material 3, Cupertino and Fluent palettes built in, and
  a Design beside them for shape, sizing and motion.
• A software rasteriser with antialiasing, gradients and clipping, and an
  SVG writer for review and golden images.
• The interaction layer in full: hover, press, click, focus,
  :focus-visible, focus-within, Tab traversal, wheel routing and per-node
  cursors.
• An animation clock on CSS's transition model — a component says where a
  value should be, not how to get there.
• Around fifty components, from a button to a table, a rich-text editor and
  eight kinds of chart, all stateless functions themed by token.
• One allocation per frame: nodes live in an arena addressed by index, so
  building a tree is a push_back and releasing one is a reset.

The component set as data

• gbui::meta describes every component — its group, its documentation, its
  signature, and each option with type, default and doc — generated from the
  headers by tools/generate_meta.py, so a table nobody maintains cannot fall
  behind the code it describes. CI regenerates it and fails on a difference.

Demos and documentation

• Six application screens built from the public headers alone: a revenue
  dashboard, a weather desk, a plant supervisory HMI, a production line monitor,
  a grid control desk and a logistics control tower. They link gbui::gbui and
  nothing else, so a change that makes them awkward has made the library
  awkward.
• The demos run in the browser through WebAssembly, rasterised on the CPU
  into a <canvas> — the same source, with no DOM inside the rectangle.
• A documentation site on VitePress, published per version: the current
  release at the root and every archived one at its own address, built from its
  own tag.
• The source is shown first and the screen runs when the reader asks, so nothing
  downloads until they press Run.

Build and packaging

• Installable with CMake, as a static or shared library, and consumed from
  outside the tree in CI to prove the install actually works.
• SDL2 is optional: without it everything still builds and every test still
  passes, and only Window::create changes.
• CI builds, tests, sanitises and lints on Linux, macOS and Windows, with
  warnings as errors.

Fixed

• Every std::optional in an options struct has a default member initialiser,
  so a designated-initialiser call site cannot leave one indeterminate.
• Four things that only writing six screens against the library could find — see
  acf2897.
• The runner works on a fresh machine and on MSVC; the gallery example the
  gitignore was hiding is committed.

Known at the time

• No accessibility tree, and no bridge for a screen reader.
• No text shaping, so Arabic, Devanagari and emoji are wrong.
• No GPU painter — the Painter interface is six methods precisely so one can
  be written.
• No image decoding.