Goal:

Generate compilable elm-css code from valid css. In cases that elm-css does not have support for something:

• fall back to using custom functions like selector or property when able
• skip entirely (like at-rules) and warn

Things to support:

• property names

  • single arity (color, display, etc.)
  • multiple arities (padding, flex, etc.)
  • can take lists as args (font-family, etc.)
  • displayFlex

• values

  • lengths (px, in, etc)
  • angles (deg, rad, etc)
  • transforms (rotate, scale, etc. )
  • color values (rgb, hsl, elm-css Css.Colors)
  • length calculations (|+|, |/|, etc) http://www.w3schools.com/cssref/func_calc.asp
  • integers and floats
  • TextAlign
  • VerticalAlign
  • feature tags https://developer.mozilla.org/en-US/docs/Web/CSS/font-feature-settings
  • LengthOrNumber
  • values with arity 0

• selectors

  • class
  • id
  • html elements
  • combinators https://developer.mozilla.org/en-US/docs/Web/CSS/Adjacent_sibling_selectors
  • attribute selectors https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors
  • universal selectors https://developer.mozilla.org/en-US/docs/Web/CSS/Universal_selectors
  • pseudo classes https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-classes

• media queries

• important

• code comments

• at-rules (only @keyframes) not currently supported by elm-css

• use other postcss plugins

• use other postcss parsers

• validation for property and their param types