discourse/app/assets/stylesheets/common/foundation/mixins.scss

// --------------------------------------------------
// Mixins used throughout the theme
// --------------------------------------------------

// Media queries
// --------------------------------------------------

$breakpoints: (
  mobile-small: 320px,
  mobile-medium: 350px,
  mobile-large: 450px,
  mobile-extra-large: 550px,
  tablet: 768px,
  medium: 850px,
  large: 1000px,
  extra-large: 1140px,
);

@mixin breakpoint($bp, $rule: max-width, $type: screen, $sidebar: false) {
  @media #{$type} and (#{$rule}: map-get($breakpoints, $bp)) {
    @content;
  }

  // if you want to consider the sidebar in your breakpoint
  // you can pass in $sidebar: true
  // note that your breakpoint will need to be at the root level
  @if $sidebar {
    // when the sidebar is shown, we want to increase the breakpoints by the width of the sidebar
    @media #{$type} and (#{$rule}: calc(#{map-get($breakpoints, $bp)} + #{$d-sidebar-width})) {
      .has-sidebar-page {
        @content;
      }
    }
  }
}

// CSS3 properties
// --------------------------------------------------

// Clearfix

@mixin clearfix() {
  &:before,
  &:after {
    content: "";
    display: table;
  }
  &:after {
    clear: both;
  }
}

//noinspection CssOptimizeSimilarProperties
@mixin linear-gradient($start-color, $end-color) {
  background-color: $start-color;
  background-image: linear-gradient(to bottom, $start-color, $end-color);
}

// Visibility
// --------------------------------------------------

// Only shows hover on non-touch devices
@mixin hover {
  .discourse-no-touch & {
    &:hover,
    &.btn-hover {
      @content;
    }
  }
}

@mixin ellipsis {
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
}

@mixin line-clamp($lines) {
  display: -webkit-box;
  overflow: hidden;
  text-overflow: ellipsis;
  word-wrap: break-word;
  -webkit-line-clamp: $lines;
  -moz-box-orient: vertical;
  -webkit-box-orient: vertical;
}

//
// --------------------------------------------------

$vpad: 0.5em;
$hpad: 0.65em;

// for consistent sizing across inputs, buttons and dropdowns
@mixin form-item-sizing {
  border: 1px solid transparent;
  font-size: var(--font-0);
  line-height: normal;
  box-sizing: border-box;
  padding: $vpad $hpad;
  .ios-device & {
    font-size: var(--font-size-ios-input);
    padding-top: $vpad * 0.8;
    padding-bottom: $vpad * 0.8;
  }
}

@mixin sticky {
  position: -webkit-sticky;
  position: sticky;
}

// Unselectable (avoids unwanted selections with iPad, touch laptops, etc)

@mixin user-select($mode) {
  -webkit-user-select: $mode;
  user-select: $mode;
}

@mixin unselectable {
  @include user-select(none);
  cursor: default;
}

// Stuff we repeat
@mixin post-aside {
  border-left: 5px solid var(--primary-low);
  background-color: var(--blend-primary-secondary-5);
}

// We still need -webkit for latest iPhone and Safari
@mixin transform($transforms) {
  transform: $transforms;
}

@mixin appearance-none() {
  // resets default browser styles
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}

@mixin default-focus() {
  border-color: var(--tertiary);
  outline: 1px solid var(--tertiary);
  outline-offset: 0;
}

@mixin fa-rotate($degrees, $rotation) {
  transform: rotate($degrees);
}

/// Helper function to easily use an SVG inline in CSS
/// without encoding it to base64, saving bytes.
/// It also helps with browser support, especially for IE11.
///
/// @author Jakob Eriksen
/// @link http://codepen.io/jakob-e/pen/doMoML
/// @param {String} $svg - SVG image to encode
/// @return {String} - Encoded SVG data uri
@function svg-uri($svg) {
  $encoded: "";
  $slice: 2000;
  $index: 0;
  $loops: ceil(str-length($svg) / $slice);

  @for $i from 1 through $loops {
    $chunk: str-slice($svg, $index, $index + $slice - 1);
    $chunk: str-replace($chunk, '"', "'");
    $chunk: str-replace($chunk, "<", "%3C");
    $chunk: str-replace($chunk, ">", "%3E");
    $chunk: str-replace($chunk, "&", "%26");
    $chunk: str-replace($chunk, "#", "%23");
    $encoded: #{$encoded}#{$chunk};
    $index: $index + $slice;
  }

  @return url("data:image/svg+xml;charset=utf8,#{$encoded}");
}

/// Replace `$search` with `$replace` in `$string`
/// @author Hugo Giraudel
/// @link http://sassmeister.com/gist/1b4f2da5527830088e4d
/// @param {String} $string - Initial string
/// @param {String} $search - Substring to replace
/// @param {String} $replace ('') - New value
/// @return {String} - Updated string
@function str-replace($string, $search, $replace: "") {
  $index: str-index($string, $search);

  @if $index {
    @return str-slice($string, 1, $index - 1) + $replace +
      str-replace(
        str-slice($string, $index + str-length($search)),
        $search,
        $replace
      );
  }

  @return $string;
}

// SCSS accepts HEX or RGB colors for rgba($color, 0.5)
// CSS custom properties only accept RGB
// Example usage:

// --primary-rgb: #{hexToRGB($primary)};
// ...
// rgba(var(--primary-low-rgb), 0.5)

@function hexToRGB($hex) {
  @return red($hex), green($hex), blue($hex);
}

@function schemeType() {
  @if is-light-color-scheme() {
    @return "light";
  } @else {
    @return "dark";
  }
}

@function absolute-image-url($path) {
  // public_image_path is added by the stylesheet importer
  // it returns a CDN or subfolder path (if applicable).
  // SCSS will compile (and return the relative path) if public_image_path is missing.
  @if variable-exists(public_image_path) {
    @if (str-index("#{$path}", "/plugins") == 1) {
      $plugin_asset_path: str-replace($public_image_path, "/images", "");
      @return url("#{$plugin_asset_path}#{$path}");
    } @else {
      @return url("#{$public_image_path}#{$path}");
    }
  } @else {
    @return url("#{$path}");
  }
}

@mixin mention() {
  display: inline-block; // https://bugzilla.mozilla.org/show_bug.cgi?id=1656119
  font-size: 0.93em;
  font-weight: normal;
  color: var(--primary);
  padding: 0 0.3em 0.07em;
  background: var(--primary-low);
  border-radius: 0.6em;
  text-decoration: none;
}