Reference

The public API, one page per module. Each page lists what the module holds, the types it exports and the calls you are expected to make; the headers themselves carry the finer detail and the reasoning.

Module	Include	Holds
core	gbui/core/*.hpp	geometry, lengths, colour, cursors, JSON, vector paths
a11y	gbui/a11y/*.hpp	roles, names, states, relations, and the tree they are read into
style	gbui/style/*.hpp	style properties, themes and tokens, the design system
scene	gbui/scene/*.hpp	the node arena and the building API
layout	gbui/layout/*.hpp	flexbox, measurement, wrapping, hit testing
input	gbui/input/*.hpp	hover, press, focus, keys, text editing
anim	gbui/anim/*.hpp	the animation clock and its curves
overlay	gbui/overlay/*.hpp	where a floating box goes
paint	gbui/paint/*.hpp	display list, painters, the software rasteriser
widgets	gbui/widgets/*.hpp	components and icons
charts	gbui/widgets/chart.hpp	scales, series, and nine kinds of chart
platform	gbui/platform/*.hpp	window, event loop, fonts, image decoding, opening a URL

A module may depend on the ones above it and never on the ones below, with the two documented exceptions in Architecture → Modules.

Conventions across the API

• Failure is std::optional, with an error string where the reason matters. Nothing throws, and nothing in the public API is noexcept by accident.
• Options are structs, so call sites name what they set and defaults stay invisible. Designated initialisers must be written in declaration order.
• kAuto is a NaN meaning "decide for me". Test it with isAuto(value).
• Sizes are a Length, which converts implicitly from float: a plain number is pixels, Length::percent(25) is a share.
• Colours come from Token, resolved against the active Theme.
• Coordinates are logical pixels, with the origin at the top left. The display scale is applied once, in DisplayList::setScale.
• State belongs to the application. A component takes the value and returns what the user did to it; nothing here remembers anything between frames except Interaction and Animator, both of which the application owns.
• Identity is a string tag, never a NodeId: the tree is rebuilt every frame and only the tag survives it.