engine/theme_intent library

Steering hints for generated themes (engine v4): a small, bounded, JSON-friendly description of the look a host wants ("playful greenery" → light, green and lime, vivid, analogous).

The package never sees the user's words. A host turns them into a ThemeIntent however it likes (an on-device model, mood chips, a keyword table) and the generator narrows its seeded draws to the intent. Every guardrail still runs, so an intent can change how a theme feels but never make its keys unreadable.

• ThemeIntent.parse / ThemeIntent.fromJson accept anything and never throw: unknown keys and values are dropped and reported.
• ThemeIntent.vocabulary is the field and value list as data, with a one-line description each; ThemeIntent.jsonSchema and ThemeIntent.promptFragment are generated from it.
• ThemeIntent.reportFor lists the hints a family cannot honour.

Pure Dart (no Flutter, no dart:math).

Classes

IntentField

One field of the intent vocabulary.

IntentNote

One hint a family cannot honour, from ThemeIntent.reportFor.

IntentParseResult

ThemeIntent.parse output: the intent plus what was dropped.

IntentValue

One allowed value of a vocabulary field.

ThemeIntent

Steering hints for generated themes. Every field is optional; an empty intent means an ordinary unsteered theme.

Enums

IntentChroma

How colourful a steered theme is.

IntentColor

A named colour a host (or its model) can ask for. Each maps to an OKLCH hue range; some also lean the theme dark, light or muted when the intent does not say otherwise.

IntentFieldKind

How a vocabulary field takes values.

Constants

firstSteerableEngineVersion → const int

The first engine version that understands a ThemeIntent.

harmonyWords → const Map<HarmonyScheme, String>

Vocabulary words for the harmony schemes (stable).

steerableFamilies → const Set<ThemeFamily>

The families that honour steering at the newest engine version: every enabled family (engine v5). ThemeIntent.reportFor lists the hints a family can't follow.

Functions

brightnessAllowed(FamilyDefinition def, ThemeBrightness b) → bool

Whether def ever draws b.

familySteerableAt(ThemeFamily family, int engineVersion) → bool

Whether family follows an intent's colours at engineVersion (otherwise it takes only the name).