Bootstrap/less/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 #333;
  // 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 4-18
  &::-moz-placeholder           { color: @color; } // Firefox 19+
  &:-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
// Source: https://github.com/h5bp/html5-boilerplate/commit/aa0396eae757
.hide-text() {
  font: ~"0/0" a;
  color: transparent;
  text-shadow: none;
  background-color: transparent;
  border: 0;
}



// 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
.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-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+
          transform: rotate(@degrees);
}
.scale(@ratio) {
  -webkit-transform: scale(@ratio);
      -ms-transform: scale(@ratio); // IE9+
          transform: scale(@ratio);
}
.translate(@x; @y) {
  -webkit-transform: translate(@x, @y);
      -ms-transform: translate(@x, @y); // IE9+
          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);
}

// Backface visibility
// Prevent browsers from flickering when using CSS 3D transforms.
// Default value is `visible`, but can be changed to `hidden`
// See git pull https://github.com/dannykeane/bootstrap.git backface-visibility for examples
.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+
       -o-user-select: @select;
          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-gradient(linear, @start-percent top, @end-percent top, from(@start-color), to(@end-color)); // Safari 4+, Chrome 2+
    background-image: -webkit-linear-gradient(left, color-stop(@start-color @start-percent), color-stop(@end-color @end-percent)); // Safari 5.1+, Chrome 10+
    background-image: -moz-linear-gradient(left, @start-color @start-percent, @end-color @end-percent); // FF 3.6+
    background-image:  linear-gradient(to right, @start-color @start-percent, @end-color @end-percent); // Standard, IE10
    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-gradient(linear, left @start-percent, left @end-percent, from(@start-color), to(@end-color)); // Safari 4+, Chrome 2+
    background-image: -webkit-linear-gradient(top, @start-color, @start-percent, @end-color, @end-percent); // Safari 5.1+, Chrome 10+
    background-image:  -moz-linear-gradient(top, @start-color @start-percent, @end-color @end-percent); // FF 3.6+
    background-image: linear-gradient(to bottom, @start-color @start-percent, @end-color @end-percent); // Standard, IE10
    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+, Chrome 10+
    background-image: -moz-linear-gradient(@deg, @start-color, @end-color); // FF 3.6+
    background-image: linear-gradient(@deg, @start-color, @end-color); // Standard, IE10
  }
  .horizontal-three-colors(@start-color: #00b3ee; @mid-color: #7a43b6; @color-stop: 50%; @end-color: #c3325f) {
    background-image: -webkit-gradient(left, linear, 0 0, 0 100%, from(@start-color), color-stop(@color-stop, @mid-color), to(@end-color));
    background-image: -webkit-linear-gradient(left, @start-color, @mid-color @color-stop, @end-color);
    background-image: -moz-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-gradient(linear, 0 0, 0 100%, from(@start-color), color-stop(@color-stop, @mid-color), to(@end-color));
    background-image: -webkit-linear-gradient(@start-color, @mid-color @color-stop, @end-color);
    background-image: -moz-linear-gradient(top, @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-gradient(radial, center center, 0, center center, 460, from(@inner-color), to(@outer-color));
    background-image: -webkit-radial-gradient(circle, @inner-color, @outer-color);
    background-image: -moz-radial-gradient(circle, @inner-color, @outer-color);
    background-image: radial-gradient(circle, @inner-color, @outer-color);
    background-repeat: no-repeat;
  }
  .striped(@color: #555; @angle: 45deg) {
    background-image: -webkit-gradient(linear, 0 100%, 100% 0, color-stop(.25, rgba(255,255,255,.15)), color-stop(.25, transparent), color-stop(.5, transparent), color-stop(.5, rgba(255,255,255,.15)), color-stop(.75, rgba(255,255,255,.15)), color-stop(.75, transparent), to(transparent));
    background-image: -webkit-linear-gradient(@angle, rgba(255,255,255,.15) 25%, transparent 25%, transparent 50%, rgba(255,255,255,.15) 50%, rgba(255,255,255,.15) 75%, transparent 75%, transparent);
    background-image: -moz-linear-gradient(@angle, rgba(255,255,255,.15) 25%, transparent 25%, transparent 50%, rgba(255,255,255,.15) 50%, rgba(255,255,255,.15) 75%, transparent 75%, transparent);
    background-image: linear-gradient(@angle, rgba(255,255,255,.15) 25%, transparent 25%, transparent 50%, rgba(255,255,255,.15) 50%, rgba(255,255,255,.15) 75%, transparent 75%, transparent);
  }
}

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



// RETINA IMAGE SUPPORT
// --------------------------------------------------

// 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;
  }
}


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

// Horizontal dividers
// -------------------------
// Dividers (basically an hr) within dropdowns and nav lists
.nav-divider(@color: #e5e5e5) {
  height: 1px;
  margin: ((@line-height-computed / 2) - 1) 0;
  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;
  }
}

// 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%);
  }
}

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

  &:hover,
  &:focus,
  &:active,
  &.active {
    color: @color;
    background-color: darken(@background, 8%);
        border-color: darken(@border, 12%);
  }

  &.disabled,
  &[disabled],
  fieldset[disabled] & {
    &,
    &:hover,
    &:focus,
    &:active,
    &.active {
      background-color: @background;
          border-color: @border
    }
  }
}

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

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

.responsive-invisibility() {
  display: none !important;
  tr& { display: none !important; }
  th&,
  td& { display: none !important; }
}

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

// Centered container element
.container-fixed() {
  margin-right: auto;
  margin-left: auto;
  .clearfix();
}

// Creates a wrapper for a series of columns
.make-row(@gutter: @grid-gutter-width) {
  // Then clear the floated columns
  .clearfix();

  .container & {
    @media (min-width: @screen-small) {
      margin-left:  (@gutter / -2);
      margin-right: (@gutter / -2);
    }
  }

  // Negative margin nested rows out to align the content of columns
  .row {
    margin-left:  (@gutter / -2);
    margin-right: (@gutter / -2);
  }
}

// Generate the default columns
.make-column(@columns; @gutter: @grid-gutter-width) {
  position: relative;
  float: left;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  (@gutter / 2);
  padding-right: (@gutter / 2);
  @max-width: (@screen-small - 1);

  // Calculate width based on number of columns available
  @media (max-width: @max-width) {
    width: percentage((@columns / @grid-columns));
  }
}

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

  // Calculate width based on number of columns available
  @media (min-width: @screen-small) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

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

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

  // Calculate width based on number of columns available
  @media (min-width: @screen-medium) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

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

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

  // Calculate width based on number of columns available
  @media (min-width: @screen-large) {
    float: left;
    width: percentage((@columns / @grid-columns));
  }
}

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


// 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 {
    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,.075)); // Redeclare so transitions work
    &:focus {
      border-color: darken(@border-color, 10%);
      @shadow: inset 0 1px 1px rgba(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;
  }
}

// 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), .6);
  &:focus {
    border-color: @color;
    outline: 0;
    .box-shadow(~"inset 0 1px 1px rgba(0,0,0,.075), 0 0 8px @{color-rgba}");
  }
}