@reykjavik/hanna-css NPM

@reykjavik/hanna-css

TypeScript helpers for developers writing custom CSS additions for Hanna-based designs.

It provides a convenient helper objects for using hanna's CSS variables design tokens, and several useful functions (a.k.a. mixins) to boot.

Developers using CSS-in-JS libraries, such as styled-components or emotion, will find this library quite useful.

yarn add @reykjavik/hanna-css

Table of Contents:

Why TypeScript Instead of SASS?

TL;DR: TypeScript provides better developer ergonomics – both internally in this monorepo and outside of it, and is a more future-proof technology than SASS.

SASS has been almost an industry standard tool for templating CSS code for well over a decade now. Yet it provides poor developer experience with lackluster editor integrations, idiosyncratic syntax, extremely limited feature set, it's hard to publish and consume libraries, etc…

The web development community has been steadily moving on to other, more nimble technologies — either more vanilla "text/css" authoring, or class-name-based reverse compilers like Tailwind, or various JavaScript-based solutions (including literal CSS-in-JS).

This package provides supportive tooling for this last group, but offers also a new lightweight alternative: To author CSS using JavaScript as a templating engine, but then output it via one of the following methods:

Simple writeFileing the string result to static file
Use something like the es-to-css compiler,
Or stream it directly to the browser.

However, if SASS remains your thing you could still use this library to programmatically generate some key *.scss files with SASS variables, etc. and then @use those in the SASS files you write. You do you. ❤️

Generic CSS helpers

For convenience, @reykjavik/hanna-css re-exports all types and helper methods from the es-in-css library (excluding the JS-to-CSS "compiler").

Please refer to the es-in-css documentation for more info.

For the best developer experience, use VSCode and install the official vscode-styled-components extension. That gives you instant syntax highlighting and IntelliSense autocompletion inside css`` template literals.

You might also want to add a couple of hanna-css VSCode "snippets".

Hanna CSS Variables

The Hanna design system's CSS relies heavily on CSS custom properties (a.k.a. "CSS variables") for storing its most low-level design token values, and this package provides easy access to those variables, and helpers for generating your own.

The values of those variables are declared as part of the Hanna -basics CSS.

`hannaVars`

Syntax: hannaVars: Record<HannaCssVarToken, VariablePrinter>

Type-safe collection of CSS variables for use in your CSS code.

import { hannaVars, css } from '@reykjavik/hanna-css';

const myCss = css`
  .SomeComponent {
    background-color: ${hannaVars.theme_color_primary};
    font: ${hannaVars.font_hd_s};
    max-width: ${hannaVars.grid_6};
  }
`;
/*`
  .SomeComponent {
    background-color: var(--theme-color-primary);
    font: var(--font-hd-s);
    max-width: var(--grid-4);
  }
`*/

`hannaVarOverride`

Syntax: See es-in-css — VariableStyles.override

This function provides a type-safe way to write local overrides for the Hanna CSS variables. Use sparingly, with caution!

import { hannaVarOverride, css } from '@reykjavik/hanna-css';

const myCss = css`
  .SomeComponent {
    ${hannaVarOverride({
      color_faxafloi_100: `red`,
    })}
  }
`;
/*`
  .SomeComponent {
    --color-faxafloi-100: red;
  }
`*/

`formFieldVars`

Syntax: formFieldVars: Record<string, VariablePrinter>

Type-safe collection of CSS variables for styling FormField-derived components.

import { formFieldVars, css } from '@reykjavik/hanna-css';

const myCss = css`
  .MyFormField__input__dohicky {
    background-color: ${formFieldVars.input__background_color};
    ...other dohicky styling..
  }
`;
/*`
  .MyFormField__input__dohicky {
    background-color: var(--FormField-input--background-color);
    ...other dohicky styling...
  }
`*/

`buildVariables`

Syntax: buildVariables<T extends string>(vars: Array<T>, namespace?: string): VariableStyles<T>

A limited, pre-configured version of the makeVariables helper from es-in-css.

You can use this helper to generate custom CSS variables for your one-off component styling, using the same naming pattern as the Hanna CSS varibles, and the same type-safety as hannaVars.

import { buildVariables, rem, css } from '@reykjavik/hanna-css';

const myVars = buildVariables(['Component$$title__fontSize']);

const myCss = css`
  .Component {
    ${myVars.declare({ Component$$title__fontSize: rem(2) })}
  }
  .Component__title {
    font-size: ${myVars.vars.Component$$title__fontSize};
  }
`;
/*`
  .Component {
    --Component__title--fontSize: 2rem;
  }
  .Component__title {
    font-size: var(--Component__title--fontSize);
  }
`*/

The optional namespace parameter gets prepended to the generated CSS variable names. (NOTE: Namespaces are internally normalized to end with either -- or __.)

Thus the code example above could be rewritten like this:

const namespace = 'Component__';
const myVars = buildVariables(['title__fontSize'], namespace);

const myCss = css`
  .Component {
    ${myVars.declare({ title__fontSize: rem(2) })}
  }
  .Component__title {
    font-size: ${myVars.vars.title__fontSize};
  }
`;
/*`
  .Component {
    --Component__title--fontSize: 2rem;
  }
  .Component__title {
    font-size: var(--Component__title--fontSize);
  }
`*/

Class-Name constants

`htmlCl`

Collection of selectors with class-name-states that the <html/> element can take.

Here's how you'd use the beforeSprinkling selector to suppress flicker of unstyled/unscripted content in your server-rendered HTML, while you "progressively enhance" them after useEffect.

import { htmlCl, css } from '@reykjavik/hanna-css';

const myCss = css`
  ${htmlCl.beforeSprinkling} .MyComponent__details:not([data-sprinkled]) {
    display: none;
  }
  .MyComponent__details[data-sprinkled] {
    opacity: 0;
    height: 0;
  }
`;
/*`
  .before-sprinkling .MyComponent__details:not([data-sprinkled]) {
    display: none;
  }
  .MyComponent__details[data-sprinkled] {
    opacity: 0;
    height: 0;
  }
`*/

Other selectors: menuIsActive, menuIsOpen, menuIsClosed

Each of these properties has JSDoc comments associated with them. Refer to those for more info.

Helpful Constants

`colorThemes`

Object containing the names of the Hanna color themes.

import { colorThemes } from '@reykjavik/hanna-css';
import type { HannaColorTheme } from '@reykjavik/hanna-css';

const themeName: HannaColorTheme = colorThemes.trustworthy;

console.log(themeName);
// "trustworthy"

`colorFamilies`

Object containing the names of the Hanna base color families.

import { colorFamilies } from '@reykjavik/hanna-css';
import type { ColorFamily } from '@reykjavik/hanna-css';

const familyName: ColorFamily = colorFamilies.esja;

console.log(familyName);
// "esja"

`characters`

Object with several named unicode symbols for use in generated content (::markers, ::before texts, etc.). Includes bullets, spaces, quotes

import { characters } from '@reykjavik/hanna-css';

const { bullets, spaces, quotes } = characters;

console.log(quotes.IS.open + 'Hæ!' + quotes.IS.close);
// "„Hæ!“"

`icons`

Object with the names of the "decorative" icons available for general use with data-icon="" and data-icon-after="" attributes, and for React component icon props.

import { icons } from '@reykjavik/hanna-css';
import type { IconName } from '@reykjavik/hanna-css';

const iconName: IconName = icons.close;

console.log(iconName);
// "close"

`mq`

Object with pre-fabricated media queries.

import { mq, css } from '@reykjavik/hanna-css';

const myCss = css`
  @media ${mq.tablet_up} {
    .SomeComponent {
      width: 100%;
    }
  }
`;
/*`
@media (min-width: 760px) {
  .SomeComponent {
    width: 100%;
  }
}
`*/

Hanna CSS Env

`getCssBundleUrl`

Syntax: getCssBundleUrl(cssTokens: string | Array<CssModuleToken>, options?: CssBundleOpts): string

This methods generates a URL to load a correctly versioned CSS bundle from the Hanna Style Server.

You must pass a list of cssTokens corresponding to the Hanna design components you use on your page(s).

import { getCssBundleUrl } from '@reykjavik/hanna-css';

const cssTokens = [
  '-basics', // The required base style reset
  'Layout',
  'HeroBlock',
  'TextInput',
  'Selectbox',
  'ButtonPrimary',
  // etc…
];

const cssUrl = getCssBundleUrl(cssTokens);

NOTE: You need to remember to explicitly include the -basics token — unless you're incrementally adding single CSS tokens after the fact.

However, because of how CSS cascade works, it's strongly recommended to try and maintain (and update in-place) a single CSS <link rel="stylesheet" href="..." /> URL, instead of requesting multiple CSS bundles.

Multiple bundles usuallly work, but may occasionally fail in unpredictable ways.

Type `CssBundleOpts`

CssBundleOpts.version?: CssVersionToken

The default is always the most recent major version of the Hanna CSS files.

Use this option if you, for some reason, wish/need to pin your CSS files to an older, or more specific version folder.

const cssUrl = getCssBundleUrl(cssTokens, { version: 'v1.0.3' });

TypeScript Note: The version option is by default type-restricted to the CSS versions known at the time when the library was published. If you need to set a newer (minor/patch) CSS version, you should ideally update hanna-css for an updated version list. If that's not possible, you can pass a type-level generics paramter of true which relaxes the type restrictions a bit.

getCssBundleUrl<true>(cssTokens, { version: 'v1.13' });
/* Like this ———^^^^  */

Type `CssModuleToken`

All the currently known CSS module tokens that are available on the Hanna Style Server at the time when the library was published. If you need to load newer tokens, you should ideally update hanna-css for an updated token list. If that's not possible, you can convert your token Array to comma-delimited string.

`getEssentialHannaScripts`

Syntax: getEssentialHannaScripts: () => string

Essential Hanna styling assisting scripts. These provide flicker-free progressive enhancement for server-rendered dynamic Hanna UI compoennts, and fix some Safari-related styling issues.

Inline this script snippet as close to the top of your page's <head/> element as you can.

`styleServerUrl`

Syntax: styleServerUrl: string

Re-export from @reykjavik/hanna-utils/assets .

This URL is useful when building links linking to assets, etc, and is used internally by getCssBundleUrl()

`setStyleServerUrl`

Syntax: setStyleServerUrl: (url: string | URL) => void

Re-export from @reykjavik/hanna-utils/assets.

This updates the value of styleServerUrl globally. Use it at the top of your application if you want to load assets and CSS bundles from a custom style-server instance, e.g. during testing/staging/etc.

`targetCssVersion`

Syntax: targetCssVersion: string

The current MAJOR version of the Hanna style-server CSS files this version of @reyjkjavik/hanna-css package targets.

Primary use is for debugging/informational purposes.

`isDevMode`

Syntax: isDevMode: boolean

Convenience shorthand for process.env.NODE_ENV !== 'production', used internally in some of the exported mixins, etc.

import { isDevMode } from '@reykjavik/hanna-css';

const myCss = css`
  .SomeComponent {
    color: ${isDevMode ? 'red' : 'blue'};
  }
`;

Accessibility Helpers

`srOnly` mixin

Syntax srOnly: () => CssString

Mixin that hides an element visually, but still makes it accessible to screen readers.

import { css, srOnly } from '@reykjavik/hanna-css';

const myCss = css`
  .MyComponent__label {
    ${srOnly};
  }
`;

In the rare cases where you might need to make a sr-only element visible again, there's srOnly__undo that you can import and apply. (This can usually be avoided by using more precise selectors for the srOnly mixin.)

`srOnly_focusable` mixin

Syntax srOnly_focusable: () => CssString

Similar to the srOnly mixin, but intended for links/buttons that should become visible on keyboard focus (:focus-visible).

import { css, srOnly_focusable } from '@reykjavik/hanna-css';

const myCss = css`
  .MyComponent__skipLink {
    ${srOnly_focusable};
  }
`;

`srOnly_focusableContent` mixin

Syntax srOnly_focusableContent: () => CssString

Similar to the srOnly_focusable mixin above, but for non-interactive elements that contain buttons/links that should become visible on keyboard focus.

import { css, srOnly_focusableContent } from '@reykjavik/hanna-css';

const myCss = css`
  .MyComponent__dragdrop-controls {
    ${srOnly_focusableContent};
  }
`;

`keyboardFocusStyling` mixin

Syntax: keyboardFocusStyling: (css: string) => CssString

Generates backwards compatible selectors for :focus-visible — and also targets the class-names injected by the focus-visible polyfill

import { css, keyboardFocusStyling } from '@reykjavik/hanna-css';

const myCss = css`
  .MyComponent__cardlink {
    /* Card link styles ... */
    /* :hover styles ... */

    ${keyboardFocusStyling(css`
      outline: 2px solid currentColor;
      outline-offset: 2px;
    `)};
  }
`;

`hoverKeyboardFocusAndActiveStyling` mixin

Syntax: hoverKeyboardFocusAndActiveStyling: (css: string, options?: { notActive?: stirng }) => CssString

Generates :hover, :active and :focus-visible selectors in a backwards compatible manner. (It also targets the class-names injected by the focus-visible polyfill)

import {
  css,
  hoverKeyboardFocusAndActiveStyling,
} from '@reykjavik/hanna-css';

const myCss = css`
  .MyComponent__cardlink {
    /* Card link styles ... */

    ${hoverKeyboardFocusAndActiveStyling(css`
      border: 2px solid currentColor;
    `)};
  }
`;

By passing a second options parameter, the :active selector can be skipped.

Markup Warning Helpers

Sometimes you need to discourage certain HTML markup patterns, and Hanna provides some helpful mixin methods to that purpose.

They render a "hi-vis" outline around the current element and display a message in either ::before or ::after content.

By default, these messages are only visible in CSS rendered when isDevMode === true.

Example usage:

import { WARNING__, WARNING_message__ } from '@reykjavik/hanna-css';

export default css`
  :not(ul):not(ol) > li {
    ${WARNING__('<li/> must be inside <ol/> or <ul/>')};
  }
  ul > :not(li),
  ol > :not(li) {
    ${WARNING__('<ul/> only accepts <li/> as its children')};
  }
  /* Override the message only (emits less code) */
  ol > :not(li) {
    ${WARNING_message__('<ol/> only accepts <li/> as its children')};
  }
`;

`WARNING__`

Syntax: WARNING__(message: string, opts?: WarningOpts): string

Renders a high-priority (red) warning and message.

`WARNING_soft__`

Syntax: WARNING_soft__(message: string, opts?: WarningOpts): string

Renders a lower-priority (orange) warning and message that are only visible then the HTML element is :hovered.

`WARNING_message__`

Syntax: WARNING_soft__(message: string, ops?: Omit<WarningOpts, 'pos'>): string

Only sets (overrides) the warning message on an element that already has a warning style applied.

`WARNING_border__`

Syntax: WARNING_border__(ops?: Omit<WarningOpts, 'pos'>): string

Sets a high-priority (red) warning border around an element.

`WARNING_border_soft__`

Syntax: WARNING_border_soft__(ops?: Omit<WarningOpts, 'pos'>): string

Renders a lower-priority (orange) warning warning that is only visible then the HTML element is :hovered.

`suppress_WARNING__`

Syntax: suppress_WARNING__(ops?: WarningOpts): string

Attempts to remove warning border and message.

`suppress_WARNING_soft__`

Syntax: suppress_WARNING_soft__(ops?: WarningOpts): string

Attempts to remove lower-priority (:hover) warning border and message.

Type `WarningOpts`

The WARNING_* mixins accept an options object as their second argument.

WarningOpts.pos?: 'before' | 'after'

Default: 'before'

Controls into which ::pseudo-element the message content is rendered.

WarningOpts.always?: boolean

Default: false

Optionally make the warning messages visible in production builds also. A drastic measure reserved for highly unusual situations.

Scaling Helpers

Sometimes CSS lengths/sizes should scale lineraly with their viewport or container width. For this Hanna pprovides series of scale* and clamp* helper functions.

The clamp_ methods return a clamp(A, calc(…), B) value, while the lower-level scale* methods return a bare calc(…) value.

All of these helpers accept from and to of type ScaleEdge = PxValue | PctValue | number as their first two parameters.

Generic Scaler

`scale`

Syntax: scale(from: ScaleEdge, to: ScaleEdge, min: number | PxValue, max: number | PxValue, unit: '%' | 'vw' | 'vh'): string

This generic, low-level scale function lies at the heart of all of the other scale* and clamp* helpers.

It returns a CSS calc(…) function with slope+intercept values, that scales from from at a container/viewport size of min, up to to at a container/viewport size of max.

If the unit parameter is set to either vw/vh, then the min and max values refer to the viewport size.

import { css, px, pct } from `@reykjavik/hanna-css`
import { scale } from `@reykjavik/hanna-css/scale`

const myCSS = css`
  div {
    /* Supports "%" */
    height: ${scale(16, 24, 320, 1368, '%')};
    /* Supports "vw" (and "vh") */
    width: ${scale(16, 24, 320, 1368, 'vw')};

    /* Returns bare intercept when slopeFactor is 0 */
    margin-top: ${scale(16, 16, 320, 1368, '%')};
    /* Returns bare slope when intercept is 0 */
    margin-bottom: ${scale(16, 64, 320, 1280, 'vh')};
  }
`
/*
  div {
    /* Supports "%" */
    height: calc(0.7633587786259541% + 13.557251908396948px);
    /* Supports "vw" (and "vh") */
    width: calc(0.7633587786259541vw + 13.557251908396948px);

    /* Returns bare intercept when slopeFactor is zero */
    margin-top: 16px;
    /* Returns bare slope when intercept is zero */
    margin-bottom: 5vh;
  }
*/

Media Bracket Scalers

These generate vw-based responsive sizes, that scale linearly between two end-point sizes (number, PxValue or PctValue), within certain named media-query boundries.

clamp_phone, clamp_phablet, clamp_tablet, clamp_netbook, clamp_phone_netbook, clamp_phablet_netbook, clamp_tablet_netbook, clamp_phone_tablet, clamp_phablet_tablet, clamp_phone_phablet.

scale_phone, scale_phablet, scale_tablet, scale_netbook, scale_phone_netbook, scale_phablet_netbook, scale_tablet_netbook, scale_phone_tablet, scale_phablet_tablet, scale_phone_phablet.

Example:

import { css } from '@reykjavik/hanna-css';
import { clamp_tablet_netbook } from '@reykjavik/hanna-css/scale';

const myCSS = css`
  .CustomHeader {
    height: ${clamp_tablet_netbook(60, 120)};
  }
`;
/*
  .CustomHeader {
    height: clamp(60px, calc(9.868421052631579vw + -15px), 120px)
  }
*/

Which is effectively the same as this using the corresponding scale_* function:

import { css, mq, px } from '@reykjavik/hanna-css';
import { scale_tablet_netbook } from '@reykjavik/hanna-css/scale';

const from = px(60);
const to = px(120);

const myCSS = css`
  @media screen {
    .CustomHeader {
      height: ${from};
    }
  }
  @media screen and ${mq.tablet_netbook} {
    .CustomHeader {
      height: ${scale_tablet_netbook(from, to)};
    }
  }
  @media screen and ${mq.wide} {
    .CustomHeader {
      height: ${to};
    }
  }
`;

Container Relative Scalers

`scale_container`

Syntax: scale_container(from: ScaleEdge, to: ScaleEdge): string

This %-based scaler works for elements directly within a full-grid wide container. (As defined by Hanna's grid_raw.contentMinWidth and grid_raw.contentMaxWidth).

`scale_cols`

Syntax: scale_cols(from: ScaleEdge, to: ScaleEdge, cols: number, gutters?: number): string

Generates a %-based calc() value that scales linearly between from and to inside a container whos width is certain nubmer of grid columns and gutters.

Raw Design Constants

Using the Hanna CSS variables is highly preferable, whenever possible. However, there are always edge cases where you need access to the raw values the CSS variables build on.

For that this library exports some helpful objects.

import {
  breakpoints_raw,
  colors_raw,
  font_raw,
  grid_raw,
  iconfont_raw,
} from '@reykjavik/hanna-css';

Again use these sparingly, and deliberately.

Helpful VSCode Snippets

Here are a few code "snippets" you can add to your global snippets file to help you use hanna-css a bit faster:

  "Insert ${} variable print block": {
    "scope": "javascript,javascriptreact,typescript,typescriptreact,css",
    "prefix": "v",
    "body": "\\${$0}",
  },
  "Insert Hanna CSS variable": {
    "scope": "css",
    "prefix": "h",
    "body": "\\${hannaVars.$1};",
  },
  "Insert CSS property with Hanna varible": {
    "scope": "css",
    "prefix": "hannaprop",
    "body": "${1:css-property}: \\${hannaVars.$2};",
  },
  "css`` tagged template literal": {
    "scope": "javascript,javascriptreact,typescript,typescriptreact",
    "prefix": "css",
    "body": "css`\n\t$0\n`",
  },
  "cssVal`` tagged template literal": {
    "scope": "javascript,javascriptreact,typescript,typescriptreact",
    "prefix": "cssVal",
    "body": "cssVal`\n\t$0\n`",
  },