Package: Pretext.Contracts

Pretext.Contracts is the backend seam for Pretext. It contains the public interfaces and shared font-string parsing helpers used by first-party backends and custom integrations.

Install it when

you are implementing your own measurement backend
you want to ship a backend package independently from the core engine
you want the shared CSS-like font parser used by the first-party backends

Public surface

The package exposes:

IPretextTextMeasurer
IPretextTextMeasurerFactory
PretextTextMeasurerFactoryAttribute
PretextFontDescriptor
PretextFontParser

Backend contract shape

IPretextTextMeasurerFactory advertises:

Name
IsSupported
Priority
Create(string font)

IPretextTextMeasurer is intentionally small: it measures text width for the prepared segments that the core engine hands to it.

Shared font parsing

The first-party backends all parse the same CSS-like subset:

size in px
optional numeric weight or bold
optional italic or oblique
family list where the first family wins

Examples:

16px Inter
italic 16px Georgia
700 18px "IBM Plex Sans"

PretextFontParser.MapGenericFamily(...) also helps backend authors map system-ui, sans-serif, serif, and monospace to host-specific fallback families.

Discovery advertisement

Backends advertise their factory with an assembly-level PretextTextMeasurerFactoryAttribute. Pretext scans loaded and probeable Pretext*.dll assemblies for those attributes during runtime discovery.