mkdocs-material/src/assets/stylesheets/main/layout/_header.scss

////
/// Copyright (c) 2016-2021 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
// ----------------------------------------------------------------------------

// Header - by default, the header will be sticky and stay always on top of the
// viewport. If this behavior is not desired, just set `position: static`.
.md-header {
  position: sticky;
  top: 0;
  inset-inline: 0;
  z-index: 4;
  color: var(--md-primary-bg-color);
  background-color: var(--md-primary-fg-color);
  // Hack: reduce jitter by adding a transparent box shadow of the same size
  // so the size of the layer doesn't change during animation
  box-shadow:
    0 0           px2rem(4px) rgba(0, 0, 0, 0),
    0 px2rem(4px) px2rem(8px) rgba(0, 0, 0, 0);

  // [print]: Hide header
  @media print {
    display: none;
  }

  // Header in shadow state, i.e. shadow is visible
  &[data-md-state="shadow"] {
    box-shadow:
      0 0           px2rem(4px) rgba(0, 0, 0, 0.1),
      0 px2rem(4px) px2rem(8px) rgba(0, 0, 0, 0.2);
    transition:
      transform  250ms cubic-bezier(0.1, 0.7, 0.1, 1),
      box-shadow 250ms;
  }

  // Header in hidden state, i.e. moved out of sight
  &[data-md-state="hidden"] {
    transform: translateY(-100%);
    transition:
      transform  250ms cubic-bezier(0.8, 0, 0.6, 1),
      box-shadow 250ms;
  }

  // Header wrapper
  &__inner {
    display: flex;
    align-items: center;
    padding: 0 px2rem(4px);
  }

  // Header button
  &__button {
    position: relative;
    z-index: 1;
    margin: px2rem(4px);
    padding: px2rem(8px);
    color: currentColor;
    vertical-align: middle;
    outline-color: var(--md-accent-fg-color);
    cursor: pointer;
    transition: opacity 250ms;

    // Button on hover
    &:hover {
      opacity: 0.7;
    }

    // Header button is visible
    &:not([hidden]) {
      display: inline-block;
    }

    // Hide outline for pointer devices
    &:not(.focus-visible) {
      outline: none;
      -webkit-tap-highlight-color: transparent;
    }

    // Button with logo, pointing to `config.site_url`
    &.md-logo {
      margin: px2rem(4px);
      padding: px2rem(8px);

      // [tablet -]: Hide button
      @include break-to-device(tablet) {
        display: none;
      }

      // Image or icon
      :is(img, svg) {
        display: block;
        width: px2rem(24px);
        height: px2rem(24px);
        fill: currentColor;
      }
    }

    // Button for search
    &[for="__search"] {

      // [tablet landscape +]: Hide button
      @include break-from-device(tablet landscape) {
        display: none;
      }

      // [no-js]: Hide button
      .no-js & {
        display: none;
      }

      // Adjust for right-to-left languages
      [dir="rtl"] & svg {
        transform: scaleX(-1);
      }
    }

    // Button for drawer
    &[for="__drawer"] {

      // [screen +]: Hide button
      @include break-from-device(screen) {
        display: none;
      }
    }
  }

  // Header topic
  &__topic {
    position: absolute;
    display: flex;
    max-width: 100%;
    transition:
      transform 400ms cubic-bezier(0.1, 0.7, 0.1, 1),
      opacity   150ms;

    // Second header topic - title of the current page
    & + & {
      z-index: -1;
      transform: translateX(px2rem(25px));
      opacity: 0;
      transition:
        transform 400ms cubic-bezier(1, 0.7, 0.1, 0.1),
        opacity   150ms;
      pointer-events: none;

      // Adjust for right-to-left languages
      [dir="rtl"] & {
        transform: translateX(px2rem(-25px));
      }
    }

    // Adjust font weight of site title
    &:first-child {
      font-weight: 700;
    }
  }

  // Header title
  &__title {
    flex-grow: 1;
    height: px2rem(48px);
    margin-inline-end: px2rem(8px);
    margin-inline-start: px2rem(20px);
    font-size: px2rem(18px);
    line-height: px2rem(48px);

    // Header title in active state, i.e. page title is visible
    &[data-md-state="active"] .md-header__topic {
      z-index: -1;
      transform: translateX(px2rem(-25px));
      opacity: 0;
      transition:
        transform 400ms cubic-bezier(1, 0.7, 0.1, 0.1),
        opacity   150ms;
      pointer-events: none;

      // Adjust for right-to-left languages
      [dir="rtl"] & {
        transform: translateX(px2rem(25px));
      }

      // Second header topic - title of the current page
      + .md-header__topic {
        z-index: 0;
        transform: translateX(0);
        opacity: 1;
        transition:
          transform 400ms cubic-bezier(0.1, 0.7, 0.1, 1),
          opacity   150ms;
        pointer-events: initial;
      }
    }

    // Add ellipsis in case of overflowing text
    > .md-header__ellipsis {
      position: relative;
      width: 100%;
      height: 100%;
    }
  }

  // Header option
  &__option {
    display: flex;
    flex-shrink: 0;
    max-width: 100%;
    white-space: nowrap;
    transition:
      max-width  0ms 250ms,
      opacity  250ms 250ms;

    // Hide toggle when search is active
    [data-md-toggle="search"]:checked ~ .md-header & {
      max-width: 0;
      opacity: 0;
      transition:
        max-width 0ms,
        opacity   0ms;
    }
  }

  // Repository information container
  &__source {
    display: none;

    // [tablet landscape +]: Show repository information
    @include break-from-device(tablet landscape) {
      display: block;
      width: px2rem(234px);
      max-width: px2rem(234px);
      margin-inline-start: px2rem(20px);
    }

    // [screen +]: Adjust spacing of search bar
    @include break-from-device(screen) {
      margin-inline-start: px2rem(28px);
    }
  }
}