_modal.scss

// .modal-open      - body class for killing the scroll
// .modal           - container to scroll within
// .modal-dialog    - positioning shell for the actual modal
// .modal-content   - actual modal w/ bg and corners and stuff


// Kill the scroll on the body
.modal-open {
  overflow: hidden;
}

// Container that the modal scrolls within
.modal {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: $zindex-modal;
  display: none;
  overflow: hidden;
  // Prevent Chrome on Windows from adding a focus outline. For details, see
  // https://github.com/twbs/bootstrap/pull/10951.
  outline: 0;
  // We deliberately don't use `-webkit-overflow-scrolling: touch;` due to a
  // gnarly iOS Safari bug: https://bugs.webkit.org/show_bug.cgi?id=158342
  // See also https://github.com/twbs/bootstrap/issues/17695

  // When fading in the modal, animate it to slide down
  &.fade .modal-dialog {
    @include transition($modal-transition);
    transform: translate(0, -25%);
  }
  &.active .modal-dialog { transform: translate(0, 0); }
}
.modal-open .modal {
  overflow-x: hidden;
  overflow-y: auto;
}

// Shell div to position the modal with bottom padding
.modal-dialog {
  position: relative;
  width: auto;
  margin: $modal-dialog-margin;
}

// Actual modal
.modal-content {
  position: relative;
  background-color: $modal-content-bg;
  background-clip: padding-box;
  border: $modal-content-border-width solid $modal-content-border-color;
  @include border-radius($border-radius-lg);
  @include box-shadow($modal-content-xs-box-shadow);
  // Remove focus outline from opened modal
  outline: 0;
}

// Modal background
.modal-backdrop {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: $zindex-modal-backdrop;
  background-color: $modal-backdrop-bg;

  // Fade for backdrop