mkdocs-material/src/assets/stylesheets/layout/_nav.scss

////
/// Copyright (c) 2016-2017 Martin Donath <martin.donath@squidfunk.com>
///
/// Permission is hereby granted, free of charge, to any person obtaining a
/// copy of this software and associated documentation files (the "Software"),
/// to deal in the Software without restriction, including without limitation
/// the rights to use, copy, modify, merge, publish, distribute, sublicense,
/// and/or sell copies of the Software, and to permit persons to whom the
/// Software is furnished to do so, subject to the following conditions:
///
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
///
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
/// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
/// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
/// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
/// DEALINGS
////

// ----------------------------------------------------------------------------
// Rules
// ----------------------------------------------------------------------------

// Navigation container
.md-nav {
  font-size: ms(-1);
  line-height: 1.3;

  // Table of contents
  &--secondary {
    transition: border-left 0.25s;
    border-left: 0.4rem solid $md-color-primary;
  }

  // List title
  &__title {
    display: block;
    padding: 1.2rem 1.2rem 0;
    font-weight: 700;
    text-overflow: ellipsis;
    overflow: hidden;

    // Icon, hidden by default
    &::before {
      @extend %md-icon, %md-icon__button;

      display: none;
      content: "arrow_back";
    }

    // Hide button by default
    .md-nav__button {
      display: none;
    }
  }

  // List of items
  &__list {
    margin: 0;
    padding: 0;
    list-style: none;
  }

  // List item
  &__item {
    padding: 0.625em 1.2rem 0;

    // Add bottom spacing to last item
    &:last-child {
      padding-bottom: 1.2rem;
    }

    // 2nd+ level items
    & & {
      padding-right: 0;

      // Remove bottom spacing for nested items
      &:last-child {
        padding-bottom: 0;
      }
    }
  }

  // Icon buttons
  &__button {
    @extend %md-icon, %md-icon__button;

    // Stretch image
    img {
      width: 100%;
      height: auto;
    }
  }

  // Link inside item
  &__link {
    display: block;
    transition: color 0.125s;
    text-overflow: ellipsis;
    cursor: pointer;
    overflow: hidden;

    // Icon
    &::after {
      @extend %md-icon;

      // Item contains a nested list
      .md-nav__item--nested > & {
        content: "keyboard_arrow_down";
      }
    }

    // Hide link to table of contents by default - this will only match the
    // table of contents inside the drawer below and including tablet portrait
    html &[for="toc"] {
      display: none;

      // Hide table of contents by default
      & ~ .md-nav {
        display: none;
      }

      // Hide icon for current item
      + .md-nav__link::after {
        display: none;
      }
    }

    // Blurred item
    &[data-md-state="blur"] {
      color: $md-color-black--light;
    }

    // Active item
    &:active,
    &--active {
      color: $md-color-primary;
    }

    // Hovered item
    &:hover {
      color: $md-color-accent;
    }
  }

  // Repository containing source
  &__source {
    display: none;
  }

  // [tablet -]: Layered navigation
  @include break-to-device(tablet) {

    // Stretch primary navigation to drawer
    &--primary,
    &--primary .md-nav {
      display: flex;
      position: absolute;
      top: 0;
      right: 0;
      left: 0;
      flex-direction: column;
      height: 100%;
      z-index: 1;
    }

    // Adjust styles for primary navigation
    &--primary {
      background-color: $md-color-white;

      // Move subsequent navigations off
      .md-nav__toggle ~ .md-nav {
        @include z-depth(4);

        background-color: $md-color-white;
      }

      // List title - higher specificity is necessary to ensure that the title
      // inside the drawer is always styled accordingly
      html & .md-nav__title {
        position: relative;
        height: 11.2rem;
        padding: 6rem 1.6rem 0.4rem;
        background-color: $md-color-black--lightest;
        color: $md-color-black--light;
        font-weight: 400;
        line-height: 4.8rem;
        white-space: nowrap;
        cursor: pointer;

        // Icon
        &::before {
          display: block;
          position: absolute;
          top: 0.4rem;
          left: 0.4rem;
          width: 4rem;
          height: 4rem;
          color: $md-color-black--light;
        }

        // Main lists
        ~ .md-nav__list {

          // Pure CSS scrolling shadows, taken from
          // http://lea.verou.me/2012/04/background-attachment-local/
          background:
            linear-gradient(
              to bottom,
              $md-color-white 10%,
              $md-color-white--transparent
            ),
            linear-gradient(
              to bottom,
              $md-color-black--lighter,
              $md-color-black--lightest 35%,
              $md-color-black--transparent 60%
            );
          background-attachment: local, scroll;
          background-color: $md-color-white;
          background-repeat: no-repeat;
          background-size: 100% 2rem, 100% 1rem;

          // End of scrolling shadow definition
          box-shadow: 0 0.1rem 0 $md-color-black--lightest inset;

          // Remove border for first list item
          & > .md-nav__item:first-child {
            border-top: 0;
          }
        }

        // Site title in main navigation
        &--site {
          position: relative;
          background-color: $md-color-primary;
          color: $md-color-white;

          // Site logo
          .md-nav__button {
            display: block;
            position: absolute;
            top: 0.4rem;
            left: 0.4rem;
            width: 6.4rem;
            height: 6.4rem;
            font-size: 4.8rem;
          }

          // Hide back arrow icon
          &::before {
            display: none;
          }
        }
      }

      // List of items
      .md-nav__list {
        flex: 1;
        overflow-y: auto;
      }

      // List item
      .md-nav__item {
        padding: 0;
        border-top: 0.1rem solid $md-color-black--lightest;

        // Increase spacing to account for icon
        &--nested > .md-nav__link {
          padding-right: 4.8rem;

          // Replace icon with right arrow
          &::after {
            content: "keyboard_arrow_right";
          }
        }
      }

      // Link inside item
      .md-nav__link {
        position: relative;
        padding: 1.6rem;

        // Rotate icon
        &::after {
          position: absolute;
          top: 50%;
          right: 1.2rem;
          margin-top: -1.2rem;
          color: $md-color-black--light;
          font-size: 2.4rem;
        }

        // Color of icon should inherit link color on hover
        &:hover::after {
          color: inherit;
        }
      }

      // Set nested navigation for table of contents to static
      .md-nav--secondary .md-nav {
        position: static;

        // 3rd level link
        .md-nav__link {
          padding-left: 2.8rem;
        }

        // 4th level link
        .md-nav .md-nav__link {
          padding-left: 4rem;
        }

        // 5th level link
        .md-nav .md-nav .md-nav__link {
          padding-left: 5.2rem;
        }

        // 6th level link
        .md-nav .md-nav .md-nav .md-nav__link {
          padding-left: 6.4rem;
        }
      }
    }

    // Hide nested navigation by default
    .md-nav__toggle ~ & {
      display: none;

      // Animate appearance, if browser supports 3D transforms
      .csstransforms3d & {
        display: flex;
        transform: translateX(100%);
        transition:
          transform 0.25s cubic-bezier(0.8, 0, 0.6, 1),
          opacity   0.125s 0.05s;
        opacity: 0;
      }
    }

    // Expand nested navigation, if toggle is checked
    .md-nav__toggle:checked ~ & {
      display: flex;

      // Animate appearance, if browser supports 3D transforms
      .csstransforms3d & {
        transform: translateX(0);
        transition:
          transform 0.25s cubic-bezier(0.4, 0, 0.2, 1),
          opacity   0.125s 0.125s;
        opacity: 1;
      }
    }

    // List item
    .md-nav__title,
    .md-nav__item {
      font-size: 1.6rem;
      line-height: 1.5;
    }
  }

  // [tablet portrait -]: Show table of contents in drawer
  @include break-to-device(tablet portrait) {

    // Remove border on secondary navigation
    &--secondary {
      border-left: 0;
    }

    // Show link to table of contents - higher specificity is necessary to
    // display the table of contents inside the drawer
    html &__link[for="toc"] {
      display: block;
      padding-right: 4.8rem;

      // Unrotate icon for table of contents
      &::after {
        color: inherit;
        content: "toc";
      }

      // Hide link to current item
      + .md-nav__link {
        display: none;
      }

      // Show table of contents
      & ~ .md-nav {
        display: flex;
      }
    }

    // Repository containing source
    &__source {
      display: block;
      padding: 0.4rem;
      background-color: mix($md-color-primary, $md-color-black, 75%);
      color: $md-color-white;
    }
  }

  // [screen +]: Tree-like navigation
  @include break-from-device(screen) {

    // Animation is only possible if JavaScript is available, as the max-height
    // property must be calculated before transitioning
    &[data-md-state="animate"] {
      transition: max-height 0.25s cubic-bezier(0.86, 0, 0.07, 1);
    }

    // Hide nested navigation by default
    .md-nav__toggle ~ & {
      max-height: 0;
      overflow: hidden;
    }

    // Expand nested navigation, if toggle is checked
    .md-nav__toggle:checked ~ &,
    &[data-md-state="expand"] {
      max-height: 100%;
    }

    // Hide titles for nested navigation
    &__item--nested > .md-nav > &__title {
      display: none;
    }

    // Link inside item
    &__link {

      // Item contains a nested list
      .md-nav__item--nested > &::after {
        display: inline-block;
        transform-origin: 0.45em 0.45em;
        transform-style: preserve-3d;
        vertical-align: -0.125em;

        // Only animate icon when JavaScript is available, as the height can
        // not be animated anyway, and better no fun than half the fun
        .js & {
          transition: transform 0.4s;
        }
      }

      // Rotate icon for expanded lists
      .md-nav__item--nested .md-nav__toggle:checked ~ &::after {
        transform: rotateX(180deg);
      }
    }
  }
}