Overleaf/services/web/frontend/stylesheets/core/mixins.less

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

// Utilities
// -------------------------

// Clearfix
// Source: http://nicolasgallagher.com/micro-clearfix-hack/
//
// For modern browsers
// 1. The space content is one way to avoid an Opera bug when the
//    contenteditable attribute is included anywhere else in the document.
//    Otherwise it causes space to appear at the top and bottom of elements
//    that are clearfixed.
// 2. The use of `table` rather than `block` is only necessary if using
//    `:before` to contain the top-margins of child elements.
.clearfix() {
  &:before,
  &:after {
    content: ' '; // 1
    display: table; // 2
  }
  &:after {
    clear: both;
  }
}

// WebKit-style focus
.tab-focus() {
  // Default
  outline: thin dotted;
  // WebKit
  outline: 5px auto -webkit-focus-ring-color;
  outline-offset: -2px;
}

// Center-align a block level element
.center-block() {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

// Sizing shortcuts
.size(@width; @height) {
  width: @width;
  height: @height;
}
.square(@size) {
  .size(@size; @size);
}

// Placeholder text
.placeholder(@color: @input-color-placeholder) {
  &::-moz-placeholder {
    color: @color; // Firefox
    opacity: 1;
  } // See https://github.com/twbs/bootstrap/pull/11526
  &:-ms-input-placeholder {
    color: @color;
  } // Internet Explorer 10+
  &::-webkit-input-placeholder {
    color: @color;
  } // Safari and Chrome
}

// Text overflow
// Requires inline-block or block for proper styling
.text-overflow() {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

// CSS image replacement
//
// Heads up! v3 launched with with only `.hide-text()`, but per our pattern for
// mixins being reused as classes with the same name, this doesn't hold up. As
// of v3.0.1 we have added `.text-hide()` and deprecated `.hide-text()`. Note
// that we cannot chain the mixins together in Less, so they are repeated.
//
// Source: https://github.com/h5bp/html5-boilerplate/commit/aa0396eae757

// Deprecated as of v3.0.1 (will be removed in v4)
.hide-text() {
  font: ~'0/0' a;
  color: transparent;
  text-shadow: none;
  background-color: transparent;
  border: 0;
}
// New mixin to use as of v3.0.1
.text-hide() {
  .hide-text();
}

// CSS3 PROPERTIES
// --------------------------------------------------

// Single side border-radius
.border-top-radius(@radius) {
  border-top-right-radius: @radius;
  border-top-left-radius: @radius;
}
.border-right-radius(@radius) {
  border-bottom-right-radius: @radius;
  border-top-right-radius: @radius;
}
.border-bottom-radius(@radius) {
  border-bottom-right-radius: @radius;
  border-bottom-left-radius: @radius;
}
.border-left-radius(@radius) {
  border-bottom-left-radius: @radius;
  border-top-left-radius: @radius;
}

// Drop shadows
//
// Note: Deprecated `.box-shadow()` as of v3.1.0 since all of Bootstrap's
//   supported browsers that have box shadow capabilities now support the
//   standard `box-shadow` property.
.box-shadow(@shadow) {
  -webkit-box-shadow: @shadow; // iOS <4.3 & Android <4.1
  box-shadow: @shadow;
}

// Transitions
.transition(@transition) {
  -webkit-transition: @transition;
  transition: @transition;
}
.transition-property(@transition-property) {
  -webkit-transition-property: @transition-property;
  transition-property: @transition-property;
}
.transition-delay(@transition-delay) {
  -webkit-transition-delay: @transition-delay;
  transition-delay: @transition-delay;
}
.transition-duration(@transition-duration) {
  -webkit-transition-duration: @transition-duration;
  transition-duration: @transition-duration;
}
.transition-transform(@transition) {
  -webkit-transition: -webkit-transform @transition;
  -moz-transition: -moz-transform @transition;
  -o-transition: -o-transform @transition;
  transition: transform @transition;
}

// Transformations
.rotate(@degrees) {
  -webkit-transform: rotate(@degrees);
  -ms-transform: rotate(@degrees); // IE9 only
  transform: rotate(@degrees);
}
.scale(@ratio; @ratio-y...) {
  -webkit-transform: scale(@ratio, @ratio-y);
  -ms-transform: scale(@ratio, @ratio-y); // IE9 only
  transform: scale(@ratio, @ratio-y);
}
.translate(@x; @y) {
  -webkit-transform: translate(@x, @y);
  -ms-transform: translate(@x, @y); // IE9 only
  transform: translate(@x, @y);
}
.skew(@x; @y) {
  -webkit-transform: skew(@x, @y);
  -ms-transform: skewX(@x) skewY(@y); // See https://github.com/twbs/bootstrap/issues/4885; IE9+
  transform: skew(@x, @y);
}
.translate3d(@x; @y; @z) {
  -webkit-transform: translate3d(@x, @y, @z);
  transform: translate3d(@x, @y, @z);
}

.rotateX(@degrees) {
  -webkit-transform: rotateX(@degrees);
  -ms-transform: rotateX(@degrees); // IE9 only
  transform: rotateX(@degrees);
}
.rotateY(@degrees) {
  -webkit-transform: rotateY(@degrees);
  -ms-transform: rotateY(@degrees); // IE9 only
  transform: rotateY(@degrees);
}
.perspective(@perspective) {
  -webkit-perspective: @perspective;
  -moz-perspective: @perspective;
  perspective: @perspective;
}
.perspective-origin(@perspective) {
  -webkit-perspective-origin: @perspective;
  -moz-perspective-origin: @perspective;
  perspective-origin: @perspective;
}
.transform-origin(@origin) {
  -webkit-transform-origin: @origin;
  -moz-transform-origin: @origin;
  -ms-transform-origin: @origin; // IE9 only
  transform-origin: @origin;
}

// Animations
.animation(@animation) {
  -webkit-animation: @animation;
  animation: @animation;
}
.animation-name(@name) {
  -webkit-animation-name: @name;
  animation-name: @name;
}
.animation-duration(@duration) {
  -webkit-animation-duration: @duration;
  animation-duration: @duration;
}
.animation-timing-function(@timing-function) {
  -webkit-animation-timing-function: @timing-function;
  animation-timing-function: @timing-function;
}
.animation-delay(@delay) {
  -webkit-animation-delay: @delay;
  animation-delay: @delay;
}
.animation-iteration-count(@iteration-count) {
  -webkit-animation-iteration-count: @iteration-count;
  animation-iteration-count: @iteration-count;
}
.animation-direction(@direction) {
  -webkit-animation-direction: @direction;
  animation-direction: @direction;
}

// Backface visibility
// Prevent browsers from flickering when using CSS 3D transforms.
// Default value is `visible`, but can be changed to `hidden`
.backface-visibility(@visibility) {
  -webkit-backface-visibility: @visibility;
  -moz-backface-visibility: @visibility;
  backface-visibility: @visibility;
}

// Box sizing
.box-sizing(@boxmodel) {
  -webkit-box-sizing: @boxmodel;
  -moz-box-sizing: @boxmodel;
  box-sizing: @boxmodel;
}

// User select
// For selecting text on the page
.user-select(@select) {
  -webkit-user-select: @select;
  -moz-user-select: @select;
  -ms-user-select: @select; // IE10+
  user-select: @select;
}

// Resize anything
.resizable(@direction) {
  resize: @direction; // Options: horizontal, vertical, both
  overflow: auto; // Safari fix
}

// CSS3 Content Columns
.content-columns(@column-count; @column-gap: @grid-gutter-width) {
  -webkit-column-count: @column-count;
  -moz-column-count: @column-count;
  column-count: @column-count;
  -webkit-column-gap: @column-gap;
  -moz-column-gap: @column-gap;
  column-gap: @column-gap;
}

// Optional hyphenation
.hyphens(@mode: auto) {
  word-wrap: break-word;
  -webkit-hyphens: @mode;
  -moz-hyphens: @mode;
  -ms-hyphens: @mode; // IE10+
  -o-hyphens: @mode;
  hyphens: @mode;
}

// Opacity
.opacity(@opacity) {
  opacity: @opacity;
  // IE8 filter
  @opacity-ie: (@opacity * 100);
  filter: ~'alpha(opacity=@{opacity-ie})';
}

// GRADIENTS
// --------------------------------------------------

#gradient {
  // Horizontal gradient, from left to right
  //
  // Creates two color stops, start and end, by specifying a color and position for each color stop.
  // Color stops are not available in IE9 and below.
  .horizontal(@start-color: #555; @end-color: #333; @start-percent: 0%; @end-percent: 100%) {
    background-image: -webkit-linear-gradient(
      left,
      color-stop(@start-color @start-percent),
      color-stop(@end-color @end-percent)
    ); // Safari 5.1-6, Chrome 10+
    background-image: linear-gradient(
      to right,
      @start-color @start-percent,
      @end-color @end-percent
    ); // Standard, IE10, Firefox 16+, Opera 12.10+, Safari 7+, Chrome 26+
    background-repeat: repeat-x;
    filter: e(
      %(
        "progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=1)",
        argb(@start-color),
        argb(@end-color)
      )
    ); // IE9 and down
  }

  // Vertical gradient, from top to bottom
  //
  // Creates two color stops, start and end, by specifying a color and position for each color stop.
  // Color stops are not available in IE9 and below.
  .vertical(@start-color: #555; @end-color: #333; @start-percent: 0%; @end-percent: 100%) {
    background-image: -webkit-linear-gradient(
      top,
      @start-color @start-percent,
      @end-color @end-percent
    ); // Safari 5.1-6, Chrome 10+
    background-image: linear-gradient(
      to bottom,
      @start-color @start-percent,
      @end-color @end-percent
    ); // Standard, IE10, Firefox 16+, Opera 12.10+, Safari 7+, Chrome 26+
    background-repeat: repeat-x;
    filter: e(
      %(
        "progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)",
        argb(@start-color),
        argb(@end-color)
      )
    ); // IE9 and down
  }

  .directional(@start-color: #555; @end-color: #333; @deg: 45deg) {
    background-repeat: repeat-x;
    background-image: -webkit-linear-gradient(
      @deg,
      @start-color,
      @end-color
    ); // Safari 5.1-6, Chrome 10+
    background-image: linear-gradient(
      @deg,
      @start-color,
      @end-color
    ); // Standard, IE10, Firefox 16+, Opera 12.10+, Safari 7+, Chrome 26+
  }
  .horizontal-three-colors(@start-color: #00b3ee; @mid-color: #7a43b6; @color-stop: 50%; @end-color: #c3325f) {
    background-image: -webkit-linear-gradient(
      left,
      @start-color,
      @mid-color @color-stop,
      @end-color
    );
    background-image: linear-gradient(
      to right,
      @start-color,
      @mid-color @color-stop,
      @end-color
    );
    background-repeat: no-repeat;
    filter: e(
      %(
        "progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=1)",
        argb(@start-color),
        argb(@end-color)
      )
    ); // IE9 and down, gets no color-stop at all for proper fallback
  }
  .vertical-three-colors(@start-color: #00b3ee; @mid-color: #7a43b6; @color-stop: 50%; @end-color: #c3325f) {
    background-image: -webkit-linear-gradient(
      @start-color,
      @mid-color @color-stop,
      @end-color
    );
    background-image: linear-gradient(
      @start-color,
      @mid-color @color-stop,
      @end-color
    );
    background-repeat: no-repeat;
    filter: e(
      %(
        "progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)",
        argb(@start-color),
        argb(@end-color)
      )
    ); // IE9 and down, gets no color-stop at all for proper fallback
  }
  .radial(@inner-color: #555; @outer-color: #333) {
    background-image: -webkit-radial-gradient(
      circle,
      @inner-color,
      @outer-color
    );
    background-image: radial-gradient(circle, @inner-color, @outer-color);
    background-repeat: no-repeat;
  }
  .striped(@color: rgba(255,255,255,0.15); @angle: 45deg) {
    background-image: -webkit-linear-gradient(
      @angle,
      @color 25%,
      transparent 25%,
      transparent 50%,
      @color 50%,
      @color 75%,
      transparent 75%,
      transparent
    );
    background-image: linear-gradient(
      @angle,
      @color 25%,
      transparent 25%,
      transparent 50%,
      @color 50%,
      @color 75%,
      transparent 75%,
      transparent
    );
  }
}

// Reset filters for IE
//
// When you need to remove a gradient background, do not forget to use this to reset
// the IE filter for IE9 and below.
.reset-filter() {
  filter: e(%('progid:DXImageTransform.Microsoft.gradient(enabled = false)'));
}

// Retina images
//
// Short retina mixin for setting background-image and -size

.img-retina(@file-1x; @file-2x; @width-1x; @height-1x) {
  background-image: url('@{file-1x}');

  @media only screen and (-webkit-min-device-pixel-ratio: 2),
    only screen and (min--moz-device-pixel-ratio: 2),
    only screen and (-o-min-device-pixel-ratio: 2/1),
    only screen and (min-device-pixel-ratio: 2),
    only screen and (min-resolution: 192dpi),
    only screen and (min-resolution: 2dppx) {
    background-image: url('@{file-2x}');
    background-size: @width-1x @height-1x;
  }
}

// Responsive image
//
// Keep images from scaling beyond the width of their parents.

.img-responsive(@display: block) {
  display: @display;
  max-width: 100%; // Part 1: Set a maximum relative to the parent
  height: auto; // Part 2: Scale the height according to the width, otherwise you get stretching
}

// COMPONENT MIXINS
// --------------------------------------------------

// Horizontal dividers
// -------------------------
// Dividers (basically an hr) within dropdowns and nav lists
.nav-divider(@color: #e5e5e5) {
  height: 1px;
  margin: @dropdown-divider-margin;
  overflow: hidden;
  background-color: @color;
}

// Panels
// -------------------------
.panel-variant(@border; @heading-text-color; @heading-bg-color; @heading-border) {
  border-color: @border;

  & > .panel-heading {
    color: @heading-text-color;
    background-color: @heading-bg-color;
    border-color: @heading-border;

    + .panel-collapse .panel-body {
      border-top-color: @border;
    }
  }
  & > .panel-footer {
    + .panel-collapse .panel-body {
      border-bottom-color: @border;
    }
  }
}

// Alerts
// -------------------------
.alert-variant(@background; @border; @text-color) {
  background-color: @background;
  border-color: @border;
  color: @text-color;

  hr {
    border-top-color: darken(@border, 5%);
  }
  .alert-link {
    color: darken(@text-color, 10%);
  }

  .alert-link-as-btn {
    display: inline-block;
    font-weight: bold;
    text-decoration: none;
    .btn-alert-variant(@background);
    .button-size(
      @padding-xs-vertical; @padding-small-horizontal; @font-size-small;
        @line-height-small; @btn-border-radius-small
    );
    &:hover {
      text-decoration: none;
    }
  }

  small,
  .small {
    color: @text-color;
  }
}

.btn-alert-variant(@alert-bg) {
  .button-variant(#fff, shade(@alert-bg, 15%), transparent);
  border-radius: @btn-border-radius-base;
}

// Tables
// -------------------------
.table-row-variant(@state; @background) {
  // Exact selectors below required to override `.table-striped` and prevent
  // inheritance to nested tables.
  .table > thead > tr,
  .table > tbody > tr,
  .table > tfoot > tr {
    > td.@{state},
    > th.@{state},
    &.@{state} > td,
    &.@{state} > th {
      background-color: @background;
    }
  }

  // Hover states for `.table-hover`
  // Note: this is not available for cells or rows within `thead` or `tfoot`.
  .table-hover > tbody > tr {
    > td.@{state}:hover,
    > th.@{state}:hover,
    &.@{state}:hover > td,
    &.@{state}:hover > th {
      background-color: darken(@background, 5%);
    }
  }
}

// List Groups
// -------------------------
.list-group-item-variant(@state; @background; @color) {
  .list-group-item-@{state} {
    color: @color;
    background-color: @background;

    a& {
      color: @color;

      .list-group-item-heading {
        color: inherit;
      }

      &:hover,
      &:focus {
        color: @color;
        background-color: darken(@background, 5%);
      }
      &.active,
      &.active:hover,
      &.active:focus {
        color: #fff;
        background-color: @color;
        border-color: @color;
      }
    }
  }
}

// Button variants
// -------------------------
// Easily pump out default styles, as well as :hover, :focus, :active,
// and disabled options for all buttons
.button-variant(@color; @background; @border) {
  color: @color;
  background-color: @background;
  border-color: @border;

  .alert & {
    background-color: darken(@background, 16%);
  }

  &:hover,
  &:focus,
  &:active,
  &.active,
  &.checked,
  .open .dropdown-toggle& {
    color: @color;
    background-color: darken(@background, 8%);
    border-color: darken(@border, 12%);
    .alert & {
      background-color: darken(@background, 24%);
    }
  }
  &:active,
  &.active,
  .open .dropdown-toggle& {
    background-image: none;
  }
  &.disabled,
  &[disabled],
  fieldset[disabled] & {
    &,
    &:hover,
    &:focus,
    &:active,
    &.active {
      background-color: @background;
      border-color: @border;
    }
  }

  .badge {
    color: @background;
    background-color: @color;
  }
}
.button-outline-variant(@color) {
  color: @color;
  background-color: transparent;
  border-color: @color;

  .alert & {
    background-color: transparent;
  }

  &:hover,
  &:focus,
  &:active,
  &.active,
  &.checked,
  .open .dropdown-toggle& {
    color: @color;
    background-color: transparent;
    border-color: darken(@color, 12%);
    .alert & {
      background-color: transparent;
    }
  }
  &:active,
  &.active,
  .open .dropdown-toggle& {
    background-image: none;
  }
  &.disabled,
  &[disabled],
  fieldset[disabled] & {
    &,
    &:hover,
    &:focus,
    &:active,
    &.active {
      background-color: transparent;
      border-color: @color;
    }
  }

  .badge {
    color: transparent;
    background-color: @color;
  }
}

// Button sizes
// -------------------------
.button-size(@padding-vertical; @padding-horizontal; @font-size; @line-height; @border-radius) {
  // Remove 1px to make up for the extra px of border-bottom we've added
  padding: @padding-vertical - 1 @padding-horizontal @padding-vertical;
  font-size: @font-size;
  line-height: @line-height;
  border-radius: @border-radius;
}

// Pagination
// -------------------------
.pagination-size(@padding-vertical; @padding-horizontal; @font-size; @border-radius) {
  > li {
    > a,
    > span {
      padding: @padding-vertical @padding-horizontal;
      font-size: @font-size;
    }
    &:first-child {
      > a,
      > span {
        .border-left-radius(@border-radius);
      }
    }
    &:last-child {
      > a,
      > span {
        .border-right-radius(@border-radius);
      }
    }
  }
}

// Labels
// -------------------------
.label-variant(@color) {
  background-color: @color;
  &[href] {
    &:hover,
    &:focus {
      background-color: darken(@color, 10%);
    }
  }
}

// Contextual backgrounds
// -------------------------
.bg-variant(@color) {
  background-color: @color;
  a&:hover {
    background-color: darken(@color, 10%);
  }
}

// Typography
// -------------------------
.text-emphasis-variant(@color) {
  color: @color;
  a&:hover {
    color: darken(@color, 10%);
  }
}

// Navbar vertical align
// -------------------------
// Vertically center elements in the navbar.
// Example: an element has a height of 30px, so write out `.navbar-vertical-align(30px);` to calculate the appropriate top margin.
.navbar-vertical-align(@element-height) {
  margin-top: ((@navbar-height - @element-height) / 2);
  margin-bottom: ((@navbar-height - @element-height) / 2);
}

// Progress bars
// -------------------------
.progress-bar-variant(@color) {
  background-color: @color;
  .progress-striped & {
    #gradient > .striped();
  }
}

// Responsive utilities
// -------------------------
// More easily include all the states for responsive-utilities.less.
.responsive-visibility() {
  display: block !important;
  table& {
    display: table;
  }
  tr& {
    display: table-row !important;
  }
  th&,
  td& {
    display: table-cell !important;
  }
}

.responsive-invisibility() {
  display: none !important;
}

// Grid System
// -----------

// Centered container element
.container-fixed() {
  margin-right: auto;
  margin-left: auto;
  padding-left: (@grid-gutter-width / 2);
  padding-right: (@grid-gutter-width / 2);
  &:extend(.clearfix all);
}

// Creates a wrapper for a series of columns
.make-row(@gutter: @grid-gutter-width) {
  margin-left: (@gutter / -2);
  margin-right: (@gutter / -2);
  &:extend(.clearfix all);
}

// Generate the extra small columns
.make-xs-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  float: left;
  width: percentage((@columns / @grid-columns));
  min-height: 1px;
  padding-left: (@gutter / 2);
  padding-right: (@gutter / 2);
}
.make-xs-column-offset(@columns) {
  @media (min-width: @screen-xs-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-xs-column-push(@columns) {
  @media (min-width: @screen-xs-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-xs-column-pull(@columns) {
  @media (min-width: @screen-xs-min) {
    right: percentage((@columns / @grid-columns));
  }
}

// Generate the small columns
.make-sm-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  min-height: 1px;
  padding-left: (@gutter / 2);
  padding-right: (@gutter / 2);

  @media (min-width: @screen-sm-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}
.make-sm-column-offset(@columns) {
  @media (min-width: @screen-sm-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-sm-column-push(@columns) {
  @media (min-width: @screen-sm-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-sm-column-pull(@columns) {
  @media (min-width: @screen-sm-min) {
    right: percentage((@columns / @grid-columns));
  }
}

// Generate the medium columns
.make-md-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  min-height: 1px;
  padding-left: (@gutter / 2);
  padding-right: (@gutter / 2);

  @media (min-width: @screen-md-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}
.make-md-column-offset(@columns) {
  @media (min-width: @screen-md-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-md-column-push(@columns) {
  @media (min-width: @screen-md-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-md-column-pull(@columns) {
  @media (min-width: @screen-md-min) {
    right: percentage((@columns / @grid-columns));
  }
}

// Generate the large columns
.make-lg-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  min-height: 1px;
  padding-left: (@gutter / 2);
  padding-right: (@gutter / 2);

  @media (min-width: @screen-lg-min) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}
.make-lg-column-offset(@columns) {
  @media (min-width: @screen-lg-min) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-lg-column-push(@columns) {
  @media (min-width: @screen-lg-min) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-lg-column-pull(@columns) {
  @media (min-width: @screen-lg-min) {
    right: percentage((@columns / @grid-columns));
  }
}

// Framework grid generation
//
// Used only by Bootstrap to generate the correct number of grid classes given
// any value of `@grid-columns`.

.make-grid-columns() {
  // Common styles for all sizes of grid columns, widths 1-12
  .col(@index) when (@index = 1) {
    // initial
    @item: ~'.col-xs-@{index}, .col-sm-@{index}, .col-md-@{index}, .col-lg-@{index}';
    .col((@index + 1), @item);
  }
  .col(@index, @list) when (@index =< @grid-columns) {
    // general; "=<" isn't a typo
    @item: ~'.col-xs-@{index}, .col-sm-@{index}, .col-md-@{index}, .col-lg-@{index}';
    .col((@index + 1), ~'@{list}, @{item}');
  }
  .col(@index, @list) when (@index > @grid-columns) {
    // terminal
    @{list} {
      position: relative;
      // Prevent columns from collapsing when empty
      min-height: 1px;
      // Inner gutter via padding
      padding-left: (@grid-gutter-width / 2);
      padding-right: (@grid-gutter-width / 2);
    }
  }
  .col(1); // kickstart it
}

.float-grid-columns(@class) {
  .col(@index) when (@index = 1) {
    // initial
    @item: ~'.col-@{class}-@{index}';
    .col((@index + 1), @item);
  }
  .col(@index, @list) when (@index =< @grid-columns) {
    // general
    @item: ~'.col-@{class}-@{index}';
    .col((@index + 1), ~'@{list}, @{item}');
  }
  .col(@index, @list) when (@index > @grid-columns) {
    // terminal
    @{list} {
      float: left;
    }
  }
  .col(1); // kickstart it
}

.calc-grid-column(@index, @class, @type) when (@type = width) and (@index > 0) {
  .col-@{class}-@{index} {
    width: percentage((@index / @grid-columns));
  }
}
.calc-grid-column(@index, @class, @type) when (@type = push) {
  .col-@{class}-push-@{index} {
    left: percentage((@index / @grid-columns));
  }
}
.calc-grid-column(@index, @class, @type) when (@type = pull) {
  .col-@{class}-pull-@{index} {
    right: percentage((@index / @grid-columns));
  }
}
.calc-grid-column(@index, @class, @type) when (@type = offset) {
  .col-@{class}-offset-@{index} {
    margin-left: percentage((@index / @grid-columns));
  }
}

// Basic looping in LESS
.loop-grid-columns(@index, @class, @type) when (@index >= 0) {
  .calc-grid-column(@index, @class, @type);
  // next iteration
  .loop-grid-columns((@index - 1), @class, @type);
}

// Create grid for specific class
.make-grid(@class) {
  .float-grid-columns(@class);
  .loop-grid-columns(@grid-columns, @class, width);
  .loop-grid-columns(@grid-columns, @class, pull);
  .loop-grid-columns(@grid-columns, @class, push);
  .loop-grid-columns(@grid-columns, @class, offset);
}

// Form validation states
//
// Used in forms.less to generate the form validation CSS for warnings, errors,
// and successes.

.form-control-validation(@text-color: #555; @border-color: #ccc; @background-color: #f5f5f5) {
  // Color the label and help text
  .help-block,
  .control-label,
  .radio,
  .checkbox,
  .radio-inline,
  .checkbox-inline {
    color: @text-color;
  }
  // Set the border and box shadow on specific inputs to match
  .form-control {
    border-color: @border-color;
    .box-shadow(
      inset 0 1px 1px rgba(0, 0, 0, 0.075)
    ); // Redeclare so transitions work
    &:focus {
      border-color: darken(@border-color, 10%);
      @shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075),
        0 0 6px lighten(@border-color, 20%);
      .box-shadow(@shadow);
    }
  }
  // Set validation states also for addons
  .input-group-addon {
    color: @text-color;
    border-color: @border-color;
    background-color: @background-color;
  }
  // Optional feedback icon
  .form-control-feedback {
    color: @text-color;
  }
}

// Form control focus state
//
// Generate a customized focus state and for any input with the specified color,
// which defaults to the `@input-focus-border` variable.
//
// We highly encourage you to not customize the default value, but instead use
// this to tweak colors on an as-needed basis. This aesthetic change is based on
// WebKit's default styles, but applicable to a wider range of browsers. Its
// usability and accessibility should be taken into account with any change.
//
// Example usage: change the default blue border and shadow to white for better
// contrast against a dark gray background.

.form-control-focus(@color: @input-border-focus) {
  @color-rgba: rgba(red(@color), green(@color), blue(@color), 0.6);
  &:focus {
    border-color: @color;
    outline: 0;
    .box-shadow(~'inset 0 1px 1px rgba(0,0,0,.075), 0 0 8px @{color-rgba}');
  }
}

// Form control sizing
//
// Relative text size, padding, and border-radii changes for form controls. For
// horizontal sizing, wrap controls in the predefined grid classes. `<select>`
// element gets special love because it's special, and that's a fact!

.input-size(@input-height; @padding-vertical; @padding-horizontal; @font-size; @line-height; @border-radius) {
  height: @input-height;
  padding: @padding-vertical @padding-horizontal;
  font-size: @font-size;
  line-height: @line-height;
  border-radius: @border-radius;

  select& {
    height: @input-height;
    line-height: @input-height;
  }

  textarea&,
  select[multiple]& {
    height: auto;
  }
}

.triangle(@_, @width, @height, @color) {
  position: absolute;
  border-color: transparent;
  border-style: solid;
  width: 0;
  height: 0;
}
.triangle(top, @width, @height, @color) {
  border-width: 0 @width / 2 @height @width / 2;
  border-bottom-color: @color;
  border-left-color: transparent;
  border-right-color: transparent;
}
.triangle(bottom, @width, @height, @color) {
  border-width: @height @width / 2 0 @width / 2;
  border-top-color: @color;
  border-left-color: transparent;
  border-right-color: transparent;
}
.triangle(right, @width, @height, @color) {
  border-width: @height / 2 0 @height / 2 @width;
  border-left-color: @color;
  border-top-color: transparent;
  border-bottom-color: transparent;
}
.triangle(left, @width, @height, @color) {
  border-width: @height / 2 @width @height / 2 0;
  border-right-color: @color;
  border-top-color: transparent;
  border-bottom-color: transparent;
}

.no-outline-ring-on-click {
  &:focus,
  &:focus:active {
    outline: 0;
  }
}