electrum-theme

Electrum Theme (electrum-theme) provides basic theming support for use with electrum-arc, the Electrum Agnostic Reactive Components.

The theme system

The theme provides various objects:

• colors → raw (base) colors, used to build a palette.
• spacing → raw (base) dimensions, used to build shapes and typo.
• timing → raw (base) timing parameters, used to build transitions.

which are then used to build following higher level constructs:

• palette → semantic colors.
• shapes → dimensions used to produce shapes and geometry.
• styles → predefined styles (as sets of CSS properties).
• transitions → animations and transitions.
• typo → font-related settings.

The theme is provided to all linked electrum components through the theme property.

Theme class

The Theme class stores the information about a theme. To create an instance of a theme, use Theme.create(name) and specify one of the predefined theme configuration names (by default the theme named default will be used). The name can be specified as PascalCase, camelCase or kebab-case.

const theme = Theme.create ('dark');

Styles class

• styles → cached style object.
• usesProps → true if the style function expects properties.

API surfaced in electrum components

Usually, you won't want to interact with the Styles class directly, but rather rely on following Electrum injected functions on the component instance:

• On a component, this.resolveStyle() forwards to styles.resolve()
• On a component, this.styles returns a contextual array of style objects, depending on the props found on the component instance.

Resolving a specific style

Based on styles definition object, you can query a specific style by using styles.resolve():

• styles.resolve(name) → returns a style object or {} if it is not known.
• styles.resolve(name1, name2, ...) → returns a style object resulting in a merge of all resolved style objects, applying properties from left to right.

Color manipulation functions

Electrum Theme also exposes a ColorManipulator which contains following functions:

• fade(color, amount) → faded color done by altering the alpha channel.
• lighten(color, amount) → lighter color.
• darken(color, amount) → darker color.
• emphasize(color, amount) → darker color/lighter color (depending on the initial luminance). A dark color will become lighter. A light color will become darker.
• getLuminance(color) → the computed luminance (0...1).

import {ColorManipulator} from 'electrum-theme';

const color1 = '#00ff00';
const color2 = ColorManipulator.darken (color1, 0.2);

Unit manipulation

Unit.multiply(value, factor) can be used to multiply a value (number or standard CSS dimension specification) by a factor. Following dimensions are supported:

• px
• em and rem
• %

Styling with a theme in electrum components

electrum injects a special style getter this.styles which can be used to automatically produce a style object which can be fed to Radium.

Here is a minimal component which automatically styles its <span> element using the this.styles getter:

// hello.component.js
export default class Hello extends React.Component {
  render () {
    return <span style={this.styles}>Hello</span>;
  }
}
// hello.styles.js
export default function (theme) {
  return {
    base: {
      color: theme.colors.black,
      fontFamily: theme.typo.font
    },
    cool: {
      color: theme.colors.blue100
    }
  };
}

The user of the component can then say <Hello/> and get the component display its text in black with the theme's font (the CSS styles found in base are applied by default).

To get the bright blue (blue100) color, the user writes <Hello kind='cool'/>. The kind property specifies that the cool CSS styles have to be applied on top of the base styles for component <Hello>.

The component can also explicitly apply sub-styles (by name or directly as style objects) by applying them using function with():

let styles = this.styles;
if (disabled) {
  styles = styles.with ('disabled');
}
if (whatever) {
  styles = styles.with ('other');
}
if (x > 100) {
  styles = styles.with ({width: x*2 - 100});
}

The *.styles.js file should include style objects called disabled and other.

Inclusion of theme styles

The theme can define styles (theme.styles) which can be included using the special includes style property which lists the names of the theme styles to include:

export default function (theme) {
  return {
    base: {
      position: 'fixed',
      includes: ['fullSize'],  // <-- include style fullSize here
      backgroundColor: theme.palette.canvasColor
    }
  };
}

Computed style properties

Styles properties can be defined as functions, which can modify the style when they get applied:

export default function (theme) {
  return {
    base: {
      height: theme.spacing.lineHeight,
      // ...
    },
    small: {
      height: style => style.height * 0.8 // property defined as a function
    }
  };
}