Styling Elements

Mint includes CSS support for styling HTML elements.

Within a component, you define styles with a style block named with an identifier:

component Test {
  style base {
    font-family: sans;
    font-weight: bold;
    color: red;
  }

  fun render : Html {
    <div::base>
      Hello
    </div>
  }
}

Then you apply the styles to an HTML element by specifying it after the tag of the element <div::style/>

You can have CSS definitions, sub rules, media queries, if and case expressions inside a style block.

You can even apply multiple styles to an HTML element:

component Main {
  style a {
    color: red;
  }

  style b {
    background: blue;
  }

  fun render : Html {
    <div::a::b/>
  }
}

Interpolation

Expressions can be interpolated in the value of a property using the interpolation syntax #{...}:

component Test {
  style base {
    color: #{color};
  }

  get color : String {
    "red"
  }

  fun render : Html {
    <div::base>
      Hello
    </div>
  }
}

Here the color of the text evaluates to "red"

Arguments

A style block can take many arguments just like a function:

component Main {
  style base(color : String) {
    color: #{color};
  }

  fun render : Html {
    <div>
      <div::base("red")>
        "I am red!"
      </div>

      <div::base("blue")>
        "I am blue!"
      </div>
    </div>
  }
}

Sub rules

Additional rules that match the element can be defined in the same block:

component Test {
  style base {
    color: cyan;

    /* The ampersand character references the rule it resides in. */
    &:focus {
      color: red;
    }

    /* This is a sub rule which uses the descendant selector. */
    a {
      color: blue;
    }
  }

  fun render : Html {
    <div::base tabindex="0">
      <{ "Hello " }>
      <a>
        <{ "world" }>
      </a>
    </div>
  }
}

This is useful for styling pseudo elements and states or styling child elements.

@media

Media queries can be defined for a style or sub rule. When matched, their contents apply to all elements that match them.

component Test {
  style base {
    color: red;

    @media (min-width: 600px) {
      color: blue;
    }
  }
  fun render : Html {
    <div::base>
      <{ "Hello " }>
    </div>
  }
}

@supports

@supports can be defined for a style or sub rule. When matched, their contents apply to all elements that match them.

component Test {
  style base {
    color: red;

    @supports (display: grid) {
      display: grid;
    }
  }
  fun render : Html {
    <div::base>
      <{ "Hello!!" }>
    </div>
  }
}

@font-face

@font-face rules can be defined in a style block. The declaration will be global; meaning that any other component can reference that font.

component Test {
  style base {
    @font-face {
      font-family: "Open Sans";
      src: url("/fonts/OpenSans-Regular-webfont.woff2") format("woff2"),
           url("/fonts/OpenSans-Regular-webfont.woff") format("woff");
    }

    font-family: "Open Sans";
  }

  fun render : Html {
    <div::base>
      <{ "Hello!!" }>
    </div>
  }
}

@keyframes

@keyframes rules can be defined in a style block. The declaration will be global; meaning that any other component can reference that animation.

component Test {
  style base {
    @keyframes slidein {
      from {
        transform: translateX(0%);
      }

      to {
        transform: translateX(100%);
      }
    }

    animation: slidein 3s;
  }

  fun render : Html {
    <div::base>
      <{ "Hello!!" }>
    </div>
  }
}

Nesting

Sub rules , @media and @supports rules can be nested in each other infinitely:

style base {
  color: red;

  div {
    color: blue;

    @supports (display: grid) {
      display: grid;

      b {
        font-weight: normal;
      }
    }

    span {
      color: yellow;

      @media (max-width: 500px) {
        font-weight: bold;
      }
    }
  }
}

If and Case

A special version of if and case expressions can be used inside style blocks:

style base {
  if loading {
    pointer-events: none;
    opacity: 0.5;
  }

  case status {
    Status::Ok => color: blue;
    Status::Err =>
      border: 1px solid red;
      color: red;
  }
}

Style cases have some unique rules:

• one expression rule does not apply
• you can have one or more CSS definitions in each branch
• the else and empty case branch can be omitted

Inline Styles

You can use inline styles just like in HTML in two different ways:

component Main {
  fun render : Html {
    <div>
      /* As a String */
      <div style="color: red;">
        "I am red!"
      </div>

      /* As a Map(String, String) */
      let style =
        Map.empty()
        |> Map.set("color", "red")

      <div style={style}>
        "I am red!"
      </div>
    </div>
  }
}

Behind the scenes

The compiler separates properties that have interpolations from the ones that don't. The properties with interpolations are converted to use CSS variables ( --test-base-color ).

During compiling the dynamic properties are converted to use a style object that contains the appropriate variables with their expressions.

The defined styles are static and added to the head of the document at runtime.