Custom

A string from a source the library does not know about, resolved by the subclass during composition.

This is the bridge for strings that are neither literals nor Compose Multiplatform resources: Android @StringRes ids use it, and a host can extend it to read from anywhere else (a remote-config catalog, an iOS Localizable.strings lookup). Implementations should be immutable and implement equals, so an unchanged text does not recompose its component.