assets/stylesheets/font-awesome/_mixins.scss in font-awesome-sass-5.15.1 vs assets/stylesheets/font-awesome/_mixins.scss in font-awesome-sass-6.0.0

@@ -1,56 +1,73 @@
-// Mixins
+// mixins
 // --------------------------
 
+// base rendering for an icon
 @mixin fa-icon {
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
   display: inline-block;
   font-style: normal;
   font-variant: normal;
   font-weight: normal;
   line-height: 1;
 }
 
-@mixin fa-icon-rotate($degrees, $rotation) {
-  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=#{$rotation})";
-  transform: rotate($degrees);
+// sets relative font-sizing and alignment (in _sizing)
+@mixin fa-size ($font-size) {
+  font-size: fa-divide($font-size, $fa-size-scale-base) * 1em; // converts step in sizing scale into an em-based value that's relative to the scale's base
+  line-height: fa-divide(1, $font-size) * 1em; // sets the line-height of the icon back to that of it's parent
+  vertical-align: (fa-divide(6, $font-size) - fa-divide(3, 8)) * 1em; // vertically centers the icon taking into account the surrounding text's descender
 }
 
-@mixin fa-icon-flip($horiz, $vert, $rotation) {
-  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=#{$rotation}, mirror=1)";
-  transform: scale($horiz, $vert);
+// only display content to screen readers
+// see: https://www.a11yproject.com/posts/2013-01-11-how-to-hide-content/
+// see: https://hugogiraudel.com/2016/10/13/css-hide-and-seek/
+@mixin fa-sr-only() {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  margin: -1px;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  white-space: nowrap;
+  border-width: 0;
 }
 
+// use in conjunction with .sr-only to only display content when it's focused
+@mixin fa-sr-only-focusable() {
+  &:not(:focus) {
+    @include fa-sr-only();
+  }
+}
 
-// Only display content to screen readers. A la Bootstrap 4.
-//
-// See: http://a11yproject.com/posts/how-to-hide-content/
+// convenience mixins for declaring pseudo-elements by CSS variable,
+// including all style-specific font properties, and both the ::before
+// and ::after elements in the duotone case.
+@mixin fa-icon-solid($fa-var) {
+  @extend %fa-icon;
+  @extend .fa-solid;
 
-@mixin sr-only {
-  border: 0;
-  clip: rect(0, 0, 0, 0);
-  height: 1px;
-  margin: -1px;
-  overflow: hidden;
-  padding: 0;
-  position: absolute;
-  width: 1px;
+  &::before {
+    content: unquote("\"#{ $fa-var }\"");
+  }
 }
 
-// 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 fa-icon-regular($fa-var) {
+  @extend %fa-icon;
+  @extend .fa-regular;
 
-@mixin sr-only-focusable {
-  &:active,
-  &:focus {
-    clip: auto;
-    height: auto;
-    margin: 0;
-    overflow: visible;
-    position: static;
-    width: auto;
+  &::before {
+    content: unquote("\"#{ $fa-var }\"");
   }
 }
+
+@mixin fa-icon-brands($fa-var) {
+  @extend %fa-icon;
+  @extend .fa-brands;
+
+  &::before {
+    content: unquote("\"#{ $fa-var }\"");
+  }
+}
+