Bootstrap/less/input-groups.less

//
// Input groups
// --------------------------------------------------

// Base styles
// -------------------------
.input-group {
  position: relative; // For dropdowns
  display: table;
  border-collapse: separate; // prevent input groups from inheriting border styles from table cells when placed within a table

  // Undo padding and float of grid classes
  &.col {
    float: none;
    padding-left: 0;
    padding-right: 0;
  }

  .form-control {
    width: 100%;
    margin-bottom: 0;
  }
}

// Display as table-cell
// -------------------------
.input-group-addon,
.input-group-btn,
.input-group .form-control {
  display: table-cell;

  &:not(:first-child):not(:last-child) {
    border-radius: 0;
  }
}
// Addon and addon wrapper for buttons
.input-group-addon,
.input-group-btn {
  width: 1%;
  white-space: nowrap;
  vertical-align: middle; // Match the inputs
}

// Text input groups
// -------------------------
.input-group-addon {
  .box-sizing(border-box);
  padding: @padding-base-vertical @padding-base-horizontal;
  font-size: @font-size-base;
  font-weight: normal;
  line-height: @line-height-base;
  text-align: center;
  background-color: @gray-lighter;
  border: 1px solid @input-group-addon-border-color;
  border-radius: @border-radius-base;

  // Sizing
  &.input-small {
    padding: @padding-small-vertical @padding-small-horizontal;
    font-size: @font-size-small;
    border-radius: @border-radius-small;
    line-height: @line-height-small;
  }
  &.input-large {
    padding: @padding-large-vertical @padding-large-horizontal;
    font-size: @font-size-large;
    border-radius: @border-radius-large;
    line-height: @line-height-large;
  }

  // Nuke default margins from checkboxes and radios to vertically center within.
  input[type="radio"],
  input[type="checkbox"] {
    margin-top: 0;
  }
}

// Reset rounded corners
.input-group .form-control:first-child,
.input-group-addon:first-child,
.input-group-btn:first-child > .btn,
.input-group-btn:first-child > .dropdown-toggle,
.input-group-btn:last-child > .btn:not(:last-child):not(.dropdown-toggle) {
  .border-right-radius(0);
}
.input-group-addon:first-child {
  border-right: 0;
}
.input-group .form-control:last-child,
.input-group-addon:last-child,
.input-group-btn:last-child > .btn,
.input-group-btn:last-child > .dropdown-toggle,
.input-group-btn:first-child > .btn:not(:first-child) {
  .border-left-radius(0);
}
.input-group-addon:last-child {
  border-left: 0;
}

// Button input groups
// -------------------------
.input-group-btn {
  position: relative;
  white-space: nowrap;
}
.input-group-btn > .btn {
  position: relative;
  // Jankily prevent input button groups from wrapping
  + .btn {
    margin-left: -4px;
  }
  // Bring the "active" button to the front
  &:hover,
  &:active {
    z-index: 2;
  }
}