Mutable StyleSheets provide a context in which many styles can be created using a DSL.
Mutable StyleSheets provide a context in which many styles can be created using a DSL.
They are mutable because they maintain a list of registered styles, meaning you can declare each style one at a time instead of having to create a list of styles in a single expression.
Each style itself is immutable.
TODO Doc & test MutableRegister and friends inc. Style[FC]
Performs magic using mutability and side-effects so that ........
Thread-safe.