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;
     -moz-transition: @transition;
       -o-transition: @transition;
          transition: @transition;
}
.transition-delay(@transition-delay) {
  -webkit-transition-delay: @transition-delay;
     -moz-transition-delay: @transition-delay;
       -o-transition-delay: @transition-delay;
          transition-delay: @transition-delay;
}
.transition-duration(@transition-duration) {
  -webkit-transition-duration: @transition-duration;
     -moz-transition-duration: @transition-duration;
       -o-transition-duration: @transition-duration;
          transition-duration: @transition-duration;
}

// Transformations
.rotate(@degrees) {
  -webkit-transform: rotate(@degrees);
     -moz-transform: rotate(@degrees);
      -ms-transform: rotate(@degrees);
       -o-transform: rotate(@degrees);
          transform: rotate(@degrees);
}
.scale(@ratio) {
  -webkit-transform: scale(@ratio);
     -moz-transform: scale(@ratio);
      -ms-transform: scale(@ratio);
       -o-transform: scale(@ratio);
          transform: scale(@ratio);
}
.translate(@x, @y) {
  -webkit-transform: translate(@x, @y);
     -moz-transform: translate(@x, @y);
      -ms-transform: translate(@x, @y);
       -o-transform: translate(@x, @y);
          transform: translate(@x, @y);
}
.skew(@x, @y) {
  -webkit-transform: skew(@x, @y);
     -moz-transform: skew(@x, @y);
      -ms-transform: skewX(@x) skewY(@y); // See https://github.com/twitter/bootstrap/issues/4885
       -o-transform: skew(@x, @y);
          transform: skew(@x, @y);
  -webkit-backface-visibility: hidden; // See https://github.com/twitter/bootstrap/issues/5319
}
.translate3d(@x, @y, @z) {
  -webkit-transform: translate3d(@x, @y, @z);
     -moz-transform: translate3d(@x, @y, @z);
       -o-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;
}

// Background clipping
.background-clip(@clip) {
  -webkit-background-clip: @clip;
     -moz-background-clip: @clip;
          background-clip: @clip;
}

// Background sizing
.background-size(@size) {
  -webkit-background-size: @size;
     -moz-background-size: @size;
       -o-background-size: @size;
          background-size: @size;
}

// 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;
       -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;
       -o-hyphens: @mode;
          hyphens: @mode;
}

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



// BACKGROUNDS
// --------------------------------------------------

// Gradients
#gradient {
  .horizontal(@startColor: #555, @endColor: #333) {
    background-color: @endColor;
    background-image: -moz-linear-gradient(left, @startColor, @endColor); // FF 3.6+
    background-image: -webkit-gradient(linear, 0 0, 100% 0, from(@startColor), to(@endColor)); // Safari 4+, Chrome 2+
    background-image: -webkit-linear-gradient(left, @startColor, @endColor); // Safari 5.1+, Chrome 10+
    background-image: -o-linear-gradient(left, @startColor, @endColor); // Opera 11.10
    background-image: linear-gradient(to right, @startColor, @endColor); // Standard, IE10
    background-repeat: repeat-x;
    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=1)",argb(@startColor),argb(@endColor))); // IE9 and down
  }
  .vertical(@startColor: #555, @endColor: #333) {
    background-color: @endColor;
    background-image: -moz-linear-gradient(top, @startColor, @endColor); // FF 3.6+
    background-image: -webkit-gradient(linear, 0 0, 0 100%, from(@startColor), to(@endColor)); // Safari 4+, Chrome 2+
    background-image: -webkit-linear-gradient(top, @startColor, @endColor); // Safari 5.1+, Chrome 10+
    background-image: -o-linear-gradient(top, @startColor, @endColor); // Opera 11.10
    background-image: linear-gradient(to bottom, @startColor, @endColor); // Standard, IE10
    background-repeat: repeat-x;
    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)",argb(@startColor),argb(@endColor))); // IE9 and down
  }
  .directional(@startColor: #555, @endColor: #333, @deg: 45deg) {
    background-color: @endColor;
    background-repeat: repeat-x;
    background-image: -moz-linear-gradient(@deg, @startColor, @endColor); // FF 3.6+
    background-image: -webkit-linear-gradient(@deg, @startColor, @endColor); // Safari 5.1+, Chrome 10+
    background-image: -o-linear-gradient(@deg, @startColor, @endColor); // Opera 11.10
    background-image: linear-gradient(@deg, @startColor, @endColor); // Standard, IE10
  }
  .horizontal-three-colors(@startColor: #00b3ee, @midColor: #7a43b6, @colorStop: 50%, @endColor: #c3325f) {
    background-color: mix(@midColor, @endColor, 80%);
    background-image: -webkit-gradient(left, linear, 0 0, 0 100%, from(@startColor), color-stop(@colorStop, @midColor), to(@endColor));
    background-image: -webkit-linear-gradient(left, @startColor, @midColor @colorStop, @endColor);
    background-image: -moz-linear-gradient(left, @startColor, @midColor @colorStop, @endColor);
    background-image: -o-linear-gradient(left, @startColor, @midColor @colorStop, @endColor);
    background-image: linear-gradient(to right, @startColor, @midColor @colorStop, @endColor);
    background-repeat: no-repeat;
    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=1)",argb(@startColor),argb(@endColor))); // IE9 and down, gets no color-stop at all for proper fallback
  }

  .vertical-three-colors(@startColor: #00b3ee, @midColor: #7a43b6, @colorStop: 50%, @endColor: #c3325f) {
    background-color: mix(@midColor, @endColor, 80%);
    background-image: -webkit-gradient(linear, 0 0, 0 100%, from(@startColor), color-stop(@colorStop, @midColor), to(@endColor));
    background-image: -webkit-linear-gradient(@startColor, @midColor @colorStop, @endColor);
    background-image: -moz-linear-gradient(top, @startColor, @midColor @colorStop, @endColor);
    background-image: -o-linear-gradient(@startColor, @midColor @colorStop, @endColor);
    background-image: linear-gradient(@startColor, @midColor @colorStop, @endColor);
    background-repeat: no-repeat;
    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)",argb(@startColor),argb(@endColor))); // IE9 and down, gets no color-stop at all for proper fallback
  }
  .radial(@innerColor: #555, @outerColor: #333) {
    background-color: @outerColor;
    background-image: -webkit-gradient(radial, center center, 0, center center, 460, from(@innerColor), to(@outerColor));
    background-image: -webkit-radial-gradient(circle, @innerColor, @outerColor);
    background-image: -moz-radial-gradient(circle, @innerColor, @outerColor);
    background-image: -o-radial-gradient(circle, @innerColor, @outerColor);
    background-image: radial-gradient(circle, @innerColor, @outerColor);
    background-repeat: no-repeat;
  }
  .striped(@color: #555, @angle: 45deg) {
    background-color: @color;
    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: -o-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
.reset-filter() {
  filter: e(%("progid:DXImageTransform.Microsoft.gradient(enabled = false)"));
}


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

// Short retina mixin for setting background-image and -size
.retina-image(@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(@top: #e5e5e5, @bottom: #fff) {
  height: 2px; // 1px for background, one for border
  margin: ((@line-height-base / 2) - 1) 0;
  overflow: hidden;
  background-color: @top;
  border-bottom: 1px solid @bottom;
}

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

  &:hover,
  &:focus,
  &:active,
  &.active {
    background-color: darken(@background, 5%);
        border-color: darken(@border, 10%);
  }

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

// Navbar vertical align
// -------------------------
// Vertically center elements in the navbar.
// Example: an element has a height of 30px, so write out `.navbarVerticalAlign(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);
}



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

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

// Make a grid

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

  // Negative margin nested rows out to align the content of columns
  .row {
    margin-left:  (@grid-gutter-width / -2);
    margin-right: (@grid-gutter-width / -2);
  }
}
// Generate the columns
.make-column(@columns) {
  @media (min-width: @grid-float-breakpoint) {
    float: left;
    // Calculate width based on number of columns available
    width: percentage(@columns / @grid-columns);
  }
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Set inner padding as gutters instead of margin
  padding-left:  (@grid-gutter-width / 2);
  padding-right: (@grid-gutter-width / 2);
}
// Generate the column offsets
.make-column-offset(@columns) {
  @media (min-width: @grid-float-breakpoint) {
    margin-left: percentage((@columns / @grid-columns));
  }
}
.make-column-push(@columns) {
  @media (min-width: @grid-float-breakpoint) {
    left: percentage((@columns / @grid-columns));
  }
}
.make-column-pull(@columns) {
  @media (min-width: @grid-float-breakpoint) {
    right: percentage((@columns / @grid-columns));
  }
}



// The Grid
.generate-grid-columns(@grid-columns) {

  // Default columns
  .col-span-X (@index) when (@index > 0) {
    .col-span-@{index} { .col-span-(@index); }
    .col-span-X((@index - 1));
  }
  .col-span-X(0) {}

  // Offsets (gaps between columns)
  .col-offset-X (@index) when (@index > 0) {
    .col-offset-@{index} { .col-offset-(@index); }
    .col-offset-X((@index - 1));
  }
  .col-offset-X (0) {}

  // Source ordering
  .col-push-X (@index) when (@index > 0) {
    .col-push-@{index} { .col-push-(@index); }
    .col-push-X((@index - 1));
  }
  .col-push-X (0) {}

  // Source ordering
  .col-pull-X (@index) when (@index > 0) {
    .col-pull-@{index} { .col-pull-(@index); }
    .col-pull-X((@index - 1));
  }
  .col-pull-X (0) {}

  // Apply the styles
  .col-span-(@columns) {
    width: percentage((@columns / @grid-columns));
  }
  .col-offset-(@columns) {
    margin-left: percentage((@columns / @grid-columns));
  }
  .col-push-(@columns) {
    left: percentage((@columns / @grid-columns));
  }
  .col-pull-(@columns) {
    right: percentage((@columns / @grid-columns));
  }

  // Generate .spanX and .offsetX
  .col-span-X(@grid-columns);
  .col-offset-X(@grid-columns);
  .col-push-X(@grid-columns);
  .col-pull-X(@grid-columns);
}



// Framework mixins
// --------------------------------------------------

// Generate rem font-sizes with pixel fallbacks
// By default uses `@font-size-base` with an initial value of 14 (1.4rem or 14px)
.font-size(@font-size: @font-size-base) {
  @rem-size: (@font-size / 10);
  font-size: ~"@{font-size}px";
  font-size: ~"@{rem-size}rem";
}

// Generate form validation states
.formFieldState(@text-color: #555, @border-color: #ccc, @background-color: #f5f5f5) {
  // Color the label text
  .control-label {
    color: @text-color;
  }
  // Set the border and box shadow on specific inputs to match
  .input-with-feedback {
    padding-right: 32px; // to account for the feedback icon
    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);
    }
  }
}