twbs--bootstrap/scss/_popover.scss

.popover {
  position: absolute;
  top: 0;
  left: 0;
  z-index: $zindex-popover;
  display: block;
  max-width: $popover-max-width;
  // Our parent element can be arbitrary since tooltips are by default inserted as a sibling of their target element.
  // So reset our font and text properties to avoid inheriting weird values.
  @include reset-text();
  font-size: $font-size-sm;
  // Allow breaking very long words so they don't overflow the popover's bounds
  word-wrap: break-word;
  background-color: $popover-bg;
  background-clip: padding-box;
  border: $popover-border-width solid $popover-border-color;
  @include border-radius($border-radius-lg);
  @include box-shadow($popover-box-shadow);

  // Arrows
  //
  // .arrow is outer, .arrow::after is inner

  .arrow {
    position: absolute;
    display: block;
    width: $popover-arrow-width;
    height: $popover-arrow-height;
  }

  .arrow::before,
  .arrow::after {
    position: absolute;
    display: block;
    border-color: transparent;
    border-style: solid;
  }

  .arrow::before {
    content: "";
    border-width: $popover-arrow-width;
  }
  .arrow::after {
    content: "";
    border-width: $popover-arrow-width;
  }

  // Popover directions

  &.bs-popover-top {
    margin-bottom: $popover-arrow-width;

    .arrow {
      bottom: 0;
    }

    .arrow::before,
    .arrow::after {
      border-bottom-width: 0;
    }

    .arrow::before {
      bottom: -$popover-arrow-width;
      margin-left: -$popover-arrow-width;
      border-top-color: $popover-arrow-outer-color;
    }

    .arrow::after {
      bottom: calc((#{$popover-arrow-width} - #{$popover-border-width}) * -1);
      margin-left: -$popover-arrow-width;
      border-top-color: $popover-arrow-color;
    }
  }

  &.bs-popover-right {
    margin-left: $popover-arrow-width;

    .arrow {
      left: 0;
    }

    .arrow::before,
    .arrow::after {
      margin-top: -$popover-arrow-width;
      border-left-width: 0;
    }

    .arrow::before {
      left: -$popover-arrow-width;
      border-right-color: $popover-arrow-outer-color;
    }

    .arrow::after {
      left: calc((#{$popover-arrow-width} - #{$popover-border-width}) * -1);
      border-right-color: $popover-arrow-color;
    }
  }

  &.bs-popover-bottom {
    margin-top: $popover-arrow-width;

    .arrow {
      top: 0;
    }

    .arrow::before,
    .arrow::after {
      margin-left: -$popover-arrow-width;
      border-top-width: 0;
    }

    .arrow::before {
      top: -$popover-arrow-width;
      border-bottom-color: $popover-arrow-outer-color;
    }

    .arrow::after {
      top: calc((#{$popover-arrow-width} - #{$popover-border-width}) * -1);
      border-bottom-color: $popover-arrow-color;
    }

    // This will remove the popover-header's border just below the arrow
    .popover-header::before {
      position: absolute;
      top: 0;
      left: 50%;
      display: block;
      width: 20px;
      margin-left: -10px;
      content: "";
      border-bottom: $popover-border-width solid $popover-header-bg;
    }
  }

  &.bs-popover-left {
    margin-right: $popover-arrow-width;

    .arrow {
      right: 0;
    }

    .arrow::before,
    .arrow::after {
      margin-top: -$popover-arrow-width;
      border-right-width: 0;
    }

    .arrow::before {
      right: -$popover-arrow-width;
      border-left-color: $popover-arrow-outer-color;
    }

    .arrow::after {
      right: calc((#{$popover-arrow-width} - #{$popover-border-width}) * -1);
      border-left-color: $popover-arrow-color;
    }
  }
  &.bs-popover-auto {
    &[x-placement^="top"] {
      @extend .bs-popover-top;
    }
    &[x-placement^="right"] {
      @extend .bs-popover-right;
    }
    &[x-placement^="bottom"] {
      @extend .bs-popover-bottom;
    }
    &[x-placement^="left"] {
      @extend .bs-popover-left;
    }
  }
}


// Offset the popover to account for the popover arrow
.popover-header {
  padding: $popover-header-padding-y $popover-header-padding-x;
  margin-bottom: 0; // Reset the default from Reboot
  font-size: $font-size-base;
  color: $popover-header-color;
  background-color: $popover-header-bg;
  border-bottom: $popover-border-width solid darken($popover-header-bg, 5%);
  $offset-border-width: calc(#{$border-radius-lg} - #{$popover-border-width});
  @include border-top-radius($offset-border-width);

  &:empty {
    display: none;
  }
}

.popover-body {
  padding: $popover-body-padding-y $popover-body-padding-x;
  color: $popover-body-color;
}