Plass UI for Flutter

📘 plass.cdget.com

Live previews and full parameters for every component — pick Flutter in the sidebar. This README is just the quick start.

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Plass is one design language, shipped as two libraries. Every surface answers a single question — is this pressed, or does it hold something? A thing you press is tinted glass: a gradient that turns through its colour family rather than darkening, a shadow thrown in that same colour, and a bloom of light that follows your pointer across it. A thing that holds something is clear glass: translucent, deeply blurred, edged with a white hairline, never dyed. Nothing is bevelled, nothing is embossed and nothing moves when you press it — depth is carried by light, colour and blur.

This is the Flutter half. The React package is the other one, and the two hold the same components under the same names, the same parameter vocabulary and the same numbers. They version independently, so this package's number and the npm one's will not always agree.

• Finished the moment it is installed. There is no stylesheet to import, no provider to install and no theme file to fill in. A component follows the platform's brightness until a PlassTheme overrides it.
• Five parameters, not fifty. size, color, variant, density and elevation mean the same thing on every component — an md control is 40px, primary is the same family — so the tenth one costs nothing to learn after the first.
• Readable because it was measured. Every gradient stop clears 4.5:1 against its own label, the lightest corner included. A colour choice here is not a contrast bug waiting for an audit.
• Accessible without the checklist. Real semantics, focus management and keyboard activation, inside the widgets.
• Dark mode you do not write. Follows MediaQuery.platformBrightness, and can be forced either way by wrapping a subtree. No second palette, no colours redeclared.
• Nothing you did not ask for. No dependencies at all — no assets, no platform channels, no plugins. It is built on package:flutter/widgets.dart alone, so it drops into any Flutter app without bringing a second design system in behind it, and it is unaffected by material.dart and cupertino.dart moving out of the framework into material_ui and cupertino_ui.

Install

flutter pub add plass_ui

Requires Flutter 3.41 or newer (Dart 3.11).

Use

import 'package:flutter/widgets.dart';
import 'package:plass_ui/plass_ui.dart';

PlButton(
  onPressed: save,
  child: const Text('Save'),
)

PlButton(
  variant: PlassVariant.glass,
  color: PlassColor.secondary,
  size: PlassSize.lg,
  startIcon: const Icon(Icons.add),
  onPressed: newProject,
  child: const Text('New project'),
)

The page under the components

Plass draws controls and sheets. It does not paint your background — but a sheet of glass over a flat white page has nothing to be in front of, and every translucent surface in the library will read as opaque. Two tokens exist for exactly this:

final tokens = PlassTheme.of(context);

DecoratedBox(
  decoration: BoxDecoration(
    gradient: LinearGradient(
      begin: Alignment.topCenter,
      end: Alignment.bottomCenter,
      colors: <Color>[tokens.bgFrom, tokens.bgTo],
    ),
  ),
  child: ...,
)

Any backdrop with structure in it works. What does not work is nothing at all.

Dark mode

Follows MediaQuery.platformBrightness with no configuration. To force it either way, wrap a subtree:

PlassTheme(brightness: Brightness.dark, child: ...)

One thing does not change with the theme, and it is deliberate: the colour of a key. What changes is the sheet it rests on.

Development

flutter pub get
flutter test          # Widget tests
flutter analyze
cd example && flutter run   # The gallery, on any device

The gallery under example/ is also what the documentation site embeds behind every Flutter preview, and its files under example/lib/demos/ are the exact Dart the site quotes — so a snippet in the docs is code the analyser has checked.

License

MIT © CDGet