Font-Awesome/scss/_mixins.scss

// Mixins
// --------------------------

@mixin fa-icon() {
  display: inline-block;
  font: normal normal normal #{$fa-font-size-base}/#{$fa-line-height-base} FontAwesome; // shortening font declaration
  font-size: inherit; // can't have font-size inherit on line above, so need to override
  text-rendering: auto; // optimizelegibility throws things off #1094
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;

}

@mixin fa-icon-rotate($degrees, $rotation) {
  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=#{$rotation})";
  -webkit-transform: rotate($degrees);
      -ms-transform: rotate($degrees);
          transform: rotate($degrees);
}

@mixin fa-icon-flip($horiz, $vert, $rotation) {
  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=#{$rotation}, mirror=1)";
  -webkit-transform: scale($horiz, $vert);
      -ms-transform: scale($horiz, $vert);
          transform: scale($horiz, $vert);
}

// Include one icon or list of icons.
// @param {string|list}   $icon   Icon name or list of icons names to include.
@mixin fa-include-icon($icon){
    
  // Is a icon name
  @if type-of($icon) == 'string' {

    @if map-has-key($fa-iconlist, $icon) {
      .#{$fa-css-prefix}-#{$icon}:before {
        content: "#{map-get($fa-iconlist, $icon)}";
      }
    } @else {
      @warn "Unfortunately, no value could be retrieved from `#{$icon}`. "
          + "Please make sure it is defined in $fa-iconlist` map.";
    }
  
  // Is not a list and is not a string
  } @else {

    // Is a list of icons name
    @if type-of($icon) == 'list' {

      @each $name in $icon {
        @include fa-include-icon($name);
      }

    } @else {
      
      @warn "Mixin `fa-include-icons`: only can recive string or list.";

    }

  }
}


// Include all icons defineds.
@mixin fa-include-all-icons(){
  @each $name, $icon in $fa-iconlist {
    @include fa-include-icon($name);
  }
}

// Only display content to screen readers. A la Bootstrap 4.
//
// See: http://a11yproject.com/posts/how-to-hide-content/

@mixin sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  border: 0;
}

// Use in conjunction with .sr-only to only display content when it's focused.
//
// Useful for "Skip to main content" links; see http://www.w3.org/TR/2013/NOTE-WCAG20-TECHS-20130905/G1
//
// Credit: HTML5 Boilerplate

@mixin sr-only-focusable {
  &:active,
  &:focus {
    position: static;
    width: auto;
    height: auto;
    margin: 0;
    overflow: visible;
    clip: auto;
  }
}