Allow using a custom system font

[fkdarven]

Problem

Paperling currently offers five bundled font families in Settings → Appearance. These are good defaults, but users may want to use a font that is already installed on their system.

Proposed solution

Would you be open to adding a Custom font option?

A small first version could:

• Let the user enter a CSS font-family name, such as Atkinson Hyperlegible or IBM Plex Sans.
• Store the value locally alongside the existing appearance settings.
• Apply it wherever the current body-font setting is used.
• Fall back safely to Inter when the requested font is unavailable.
• Keep all five bundled font options unchanged.

To keep the initial contribution small and cross-platform, it would not import .ttf/.otf files, download web fonts, or automatically enumerate installed fonts.

Scope question

Does this fit Paperling's direction?

If so, should a custom font follow the current font setting and affect the app UI, Markdown preview, and exports, while leaving the CodeMirror source editor in JetBrains Mono?

Contribution

I would be happy to contribute the implementation if this scope is acceptable.

[Razee4315]

Yes please, go ahead. The scope you described is right.

To answer your question: follow the current font setting for the UI, preview and exports, and leave the CodeMirror editor on JetBrains Mono.

Two things to watch: keep Inter at the end of the fallback chain, and sanitize the value before it reaches CSS.