@css / css()

To style your website in Jaspr you need to write css styles alongside your html markup. See the Styling docs for a general overview of the different ways to add styling to your website.

The css utility gives you a convenient way of writing CSS style rules in Dart alongside your Jaspr components. It uses a combination of nested css selectors and Jasprs fully typed CSS bindings in Dart.

Registering style rules

When used as the @css annotation, you can register any amount of style definitions to be automatically included in your server-rendered html output (in static or server mode).

@css
final List<StyleRule> styles = [
  // Style rules in here (covered in next section)
  /* ... */
];

This is then automatically rendered to css and included in your html output after pre-rendering.

The @css annotation can be applied to the following elements:

• global variables or static fields of type List<StyleRule>
• global or static getters returning List<StyleRule>

The recommended approach is to define your styles alongside your components build() method for better locality of your code:

class App extends StatelessComponent {
  const App({super.key});

  @override
  Iterable<Component> build(BuildContext context) sync* {
    yield div(classes: 'main', [
      p([text('Hello World')]),
    ]);
  }

  @css
  static final styles = [
    css('.main', [
      css('&').box(width: 100.px),
      css('p').text(color: Colors.blue),
    ]),
  ];
}

Defining style rules

The default css() method takes a selector and a chain of Styles.

css('.main')
  .box(width: 100.px, minHeight: 100.vh)
  .text(color: Colors.black)

renders to:

.main {
  width: 100px;
  min-height: 100vh;
  color: black;
}

Nested style rules

Alternatively, calls of css() can take an additional list of nested rules like this:

css('.main', [
  css('&').box(width: 100.px),
  css('&:hover').background(color: Colors.blue),
  css('p').text(fontSize: 1.5em),
])

renders to:

.main {
  width: 100px;
}
.main:hover {
  background-color: blue;
}
.main p {
  font-size: 1.5em;
}

Nested style rules will be scoped to the parent. Using the & symbol as part of a child selector refers to the parent selector.

Style rules can also be nested any level deep.

Special style rules

In addition to the default style rule, the css utility also supports other rule variants:

css.import()

The css.import() function takes an url and renders a @import css rule:

css.import('https://fonts.googleapis.com/css?family=Roboto')

renders to:

@import url(https://fonts.googleapis.com/css?family=Roboto);

css.fontFace()

The css.fontFace() function renders a @font-face css rule.

css.fontFace(
  family: 'Roboto',
  style: FontStyle.italic,
  url: '/fonts/Roboto-italic.ttf',
)

renders to:

@font-face {
  font-family: "Roboto";
  font-style: italic;
  src: url(/fonts/Roboto-italic.ttf);
}

css.media()

The css.media() function renders a @media css rule.

css.media(MediaQuery.screen(minWidth: 1000.px), [
  css('.main').box(width: 200.px),
])

renders to:

@media screen and (min-width: 1000px) {
  .main {
    width: 200px;
  }
}