Statically typed DSL for writing css in reason.
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README.md

bs-css

Statically typed DSL for writing css in reason.

Bs-css is a statically typed interface to Emotion

Installation

npm install --save bs-css

In your bsconfig.json, include "bs-css" in the bs-dependencies.

Usage

module Styles = {
  /* Open the Css module, so we can access the style properties below without prefixing them with Css. */
  open Css;

  let card = style([
    display(flexBox),
    flexDirection(column),
    alignItems(stretch),
    backgroundColor(white),
    boxShadow(~y=px(3), ~blur=px(5), rgba(0, 0, 0, 0.3)),
    /* You can place all your theme styles in Theme.re and access as normal Reason module */
    padding(Theme.basePadding)
  ]);

  let title = style([
    fontSize(rem(1.5)),
    color(Theme.textColor),
    marginBottom(Theme.basePadding)
  ]);

  let actionButton = disabled =>
    style([
      background(disabled ? darkgray : white),
      color(black),
      border(px(1), solid, black),
      borderRadius(px(3)),
    ])
};

<div className=Styles.card>
  <h1 className=Styles.title> (ReasonReact.stringToElement("Hello")) </h1>
  <button className=Styles.actionButton(false)>
</div>

Global css

You can define global css rules with global

Css.(
  global("body", [margin(px(0))])
);

Css.(
  global("h1, h2, h3", [color(rgb(33, 33, 33))])
);

Keyframes

Define animation keyframes;

let bounce = Css.(keyframes([
  (0, [ transform( scale(0.1, 0.1) ),  opacity(0.0) ]),
  (60, [ transform( scale(1.2, 1.2) ),  opacity(1.0) ]),
  (100, [ transform( scale(1.0,1.0) ), opacity(1.0) ])
]));

let styles = Css.(style([
  animationName(bounce),
  animationDuration(2000),
  width(px(50)),
  height(px(50)),
  backgroundColor(rgb(255, 0, 0))
]));

// ...
<div className=styles>
  (ReasonReact.stringToElement("bounce!"))
</div>

Merging styles

You should avoid trying to merge styles in the same list of rules or by concatinating lists. A list of rules is converted into a JS object before being passed to Emotion where every property becomes a key in the object. This means you lose any earlier rule if you have another rule with the same property later in the list. This is especially noticable when writing sub-selectors and media queries

Trying to merge styles by just using List.concat can result in unexpected results.

This example:

let base = Css.[
  padding(px(0)),
  fontSize(px(1))
];
let overrides = Css.[
  padding(px(20)),
  fontSize(px(24)),
  color(blue)
];
let media1 = Css.[
  media("(max-width: 768px)", [
    padding(px(10))
  ])
];
let media2 = Css.[
  media("(max-width: 768px)", [
    fontSize(px(16)),
    color(red)
  ])
];
let mergedStyles = [base, overrides, media1, media2]->List.concat->Css.style;

generates the following:

.css-1nuk4bg {
  padding: 20px;
  font-size: 24px;
  color: #0000ff;
}
@media (max-width: 768px) {
  .css-1nuk4bg {
    font-size: 16px;
    color: #ff0000;
  }
}

As you can see both properties from base are overwritten (as opposed to overridden in css) and the media query in media1 is also lost because the media query from media2 overwrites it.

The merge method

merge safely merges styles by name. Uses Emotion’s cx method.

let mergedStyles =
  Css.(
    merge([
      style([
        padding(px(0)),
        fontSize(px(1))
      ]),
      style([
        padding(px(20)),
        fontSize(px(24)),
        color(blue)
      ]),
      style([
        media("(max-width: 768px)", [
          padding(px(10))
        ])
      ]),
      style([
        media("(max-width: 768px)", [
          fontSize(px(16)),
          color(red)
        ]),
      ]),
    ])
  );

Generates the following:

.css-q0lkhz {
  padding: 0px;
  font-size: 1px;
  padding: 20px;
  font-size: 24px;
  color: #0000ff;
}
@media (max-width: 768px) {
  .css-q0lkhz {
    padding: 10px;
  }
}
@media (max-width: 768px) {
  .css-q0lkhz {
    font-size: 16px;
    color: #ff0000;
  }
}

Nothing is lost and everything ends up in the final stylesheet where normal overrides apply.

Development

npm run start

Where is the documentation?

You can check out css.rei.

Thanks

Thanks to emotion which is doing all the heavy lifting.

Thanks to bs-glamor which this repo was forked from.

Thanks to elm-css for dsl design inspiration.