Handling of fonts and sizes

Status

Accepted.

Context

ADR 0016 decided that POLAR uses KERN. KERN specifies Fira Sans as its font, which raises multiple questions.

Should Fira Sans always be included, or only on demand?

• (+) We want to comply with KERN.
• (-) Users may want to deviate from it.
• (-) If the surrounding environment already provides Fira Sans, it is loaded twice.

Additionally, it has to be decided which units are used for sizes and spacings.

Decision

• Fira Sans is included by default, but can be switched off, e.g. to use the font of the surrounding environment or to avoid loading a font that is already present.
• Sizes and spacings are expressed using the KERN variables for sizes and spacings and the KERN typography scale.
• Where there is a reason not to use the KERN variables, relative units are used, that is rem instead of px, and %, em and similar where appropriate.

Consequences

• (+) POLAR complies with KERN out of the box, without further configuration.
• (+) Clients can adapt POLAR to the typography of the surrounding environment.
• (+) Duplicate loading of the font can be avoided.
• (+) Using relative units respects the font size configured by the user, which benefits accessibility.
• (o) The opt-out has to be documented for client developers.