Bootstrap/scss/_reboot.scss

// stylelint-disable at-rule-no-vendor-prefix, declaration-no-important, selector-no-qualifying-type, property-no-vendor-prefix

// Reboot
//
// Normalization of HTML elements, manually forked from Normalize.css to remove
// styles targeting irrelevant browsers while applying new styles.
//
// Normalize is licensed MIT. https://github.com/necolas/normalize.css


// Document
//
// Change from `box-sizing: content-box` so that `width` is not affected by `padding` or `border`.
*,
*::before,
*::after {
  box-sizing: border-box;
}

// Root
//
// 1. Ability to the value of the root font sizes, affecting the value of `rem`.
//    null by default, thus nothing is generated.

:root {
  font-size: $font-size-root; // 1
}

// Body
//
// 1. Remove the margin in all browsers.
// 2. As a best practice, apply a default `background-color`.
// 3. Prevent adjustments of font size after orientation changes in IE on Windows Phone and in iOS.
// 4. Change the default tap highlight to be completely transparent in iOS.
body {
  margin: 0; // 1
  font-family: $font-family-base;
  @include font-size($font-size-base);
  font-weight: $font-weight-base;
  line-height: $line-height-base;
  color: $body-color;
  text-align: $body-text-align;
  background-color: $body-bg; // 2
  -webkit-text-size-adjust: 100%; // 3
  -webkit-tap-highlight-color: rgba($black, 0); // 4
}

// Future-proof rule: in browsers that support :focus-visible, suppress the focus outline
// on elements that programmatically receive focus but wouldn't normally show a visible
// focus outline. In general, this would mean that the outline is only applied if the
// interaction that led to the element receiving programmatic focus was a keyboard interaction,
// or the browser has somehow determined that the user is primarily a keyboard user and/or
// wants focus outlines to always be presented.
//
// See https://developer.mozilla.org/en-US/docs/Web/CSS/:focus-visible
// and https://developer.paciellogroup.com/blog/2018/03/focus-visible-and-backwards-compatibility/

[tabindex="-1"]:focus:not(:focus-visible) {
  outline: 0 !important;
}


// Content grouping
//
// 1. Reset Firefox's gray color
// 2. Set correct height and prevent the `size` attribute to make the `hr` look like an input field
//    See https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_hr_size

hr {
  margin: $hr-margin-y 0;
  color: $hr-color; // 1
  background-color: currentColor;
  border: 0;
  opacity: $hr-opacity;
}

hr:not([size]) {
  height: $hr-height; // 2
}


// Typography
//
// 1. Remove top margins from headings
//    By default, `<h1>`-`<h6>` all receive top and bottom margins. We nuke the top
//    margin for easier control within type scales as it avoids margin collapsing.

%heading {
  margin-top: 0; // 1
  margin-bottom: $headings-margin-bottom;
  font-family: $headings-font-family;
  font-style: $headings-font-style;
  font-weight: $headings-font-weight;
  line-height: $headings-line-height;
  color: $headings-color;
}

h1 {
  @extend %heading;
  @include font-size($h1-font-size);
}

h2 {
  @extend %heading;
  @include font-size($h2-font-size);
}

h3 {
  @extend %heading;
  @include font-size($h3-font-size);
}

h4 {
  @extend %heading;
  @include font-size($h4-font-size);
}

h5 {
  @extend %heading;
  @include font-size($h5-font-size);
}

h6 {
  @extend %heading;
  @include font-size($h6-font-size);
}


// Reset margins on paragraphs
//
// Similarly, the top margin on `<p>`s get reset. However, we also reset the
// bottom margin to use `rem` units instead of `em`.

p {
  margin-top: 0;
  margin-bottom: $paragraph-margin-bottom;
}


// Abbreviations
//
// 1. Duplicate behavior to the data-* attribute for our tooltip plugin
// 2. Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.
// 3. Add explicit cursor to indicate changed behavior.
// 4. Prevent the text-decoration to be skipped.

abbr[title],
abbr[data-original-title] { // 1
  text-decoration: underline; // 2
  text-decoration: underline dotted; // 2
  cursor: help; // 3
  text-decoration-skip-ink: none; // 4
}


address {
  margin-bottom: 1rem;
  font-style: normal;
  line-height: inherit;
}

ol,
ul {
  padding-left: 2rem;
}

ol,
ul,
dl {
  margin-top: 0;
  margin-bottom: 1rem;
}

ol ol,
ul ul,
ol ul,
ul ol {
  margin-bottom: 0;
}

dt {
  font-weight: $dt-font-weight;
}

// 1. Undo browser default

dd {
  margin-bottom: .5rem;
  margin-left: 0; // 1
}

blockquote {
  margin: 0 0 1rem;
}

// Add the correct font weight in Chrome, Edge, and Safari

b,
strong {
  font-weight: $font-weight-bolder;
}


// Add the correct font size in all browsers

small {
  @include font-size($small-font-size);
}

// Prevent `sub` and `sup` elements from affecting the line height in
// all browsers.

sub,
sup {
  position: relative;
  @include font-size($sub-sup-font-size);
  line-height: 0;
  vertical-align: baseline;
}

sub { bottom: -.25em; }
sup { top: -.5em; }


// Links

a {
  color: $link-color;
  text-decoration: $link-decoration;

  &:hover {
    color: $link-hover-color;
    text-decoration: $link-hover-decoration;
  }
}

// And undo these styles for placeholder links/named anchors (without href).
// It would be more straightforward to just use a[href] in previous block, but that
// causes specificity issues in many other styles that are too complex to fix.
// See https://github.com/twbs/bootstrap/issues/19402

a:not([href]) {
  &,
  &:hover {
    color: inherit;
    text-decoration: none;
  }
}


// Code

pre,
code,
kbd,
samp {
  font-family: $font-family-monospace;
  @include font-size(1em); // Correct the odd `em` font sizing in all browsers.
}

// 1. Remove browser default top margin
// 2. Reset browser default of `1em` to use `rem`s
// 3. Don't allow content to break outside

pre {
  display: block;
  margin-top: 0; // 1
  margin-bottom: 1rem; // 2
  overflow: auto; // 3
  @include font-size($code-font-size);
  color: $pre-color;

  // Account for some code outputs that place code tags in pre tags
  code {
    @include font-size(inherit);
    color: inherit;
    word-break: normal;
  }
}

code {
  @include font-size($code-font-size);
  color: $code-color;
  word-wrap: break-word;

  // Streamline the style when inside anchors to avoid broken underline and more
  a > & {
    color: inherit;
  }
}

kbd {
  padding: $kbd-padding-y $kbd-padding-x;
  @include font-size($kbd-font-size);
  color: $kbd-color;
  background-color: $kbd-bg;
  @include border-radius($border-radius-sm);

  kbd {
    padding: 0;
    @include font-size(1em);
    font-weight: $nested-kbd-font-weight;
  }
}


// Figures

// Apply a consistent margin strategy (matches our type styles).

figure {
  margin: 0 0 1rem;
}


// Images and content

img {
  vertical-align: middle;
}

// 1. Workaround for the SVG overflow bug in IE 11 is still required.
//    See https://github.com/twbs/bootstrap/issues/26878

svg {
  overflow: hidden; // 1
  vertical-align: middle;
}


// Tables

// Prevent double borders

table {
  border-collapse: collapse;
}

caption {
  padding-top: $table-cell-padding;
  padding-bottom: $table-cell-padding;
  color: $table-caption-color;
  text-align: left;
  caption-side: bottom;
}

// Matches default `<td>` alignment by inheriting from the `<body>`, or the
// closest parent with a set `text-align`.

th {
  text-align: inherit;
}


// Forms

// 1. Allow labels to use `margin` for spacing.

label {
  display: inline-block; // 1
  margin-bottom: $label-margin-bottom;
}

// Remove the default `border-radius` that macOS Chrome adds.
//
// Details at https://github.com/twbs/bootstrap/issues/24093

button {
  // stylelint-disable-next-line property-blacklist
  border-radius: 0;
}

// Work around a Firefox/IE bug where the transparent `button` background
// results in a loss of the default `button` focus styles.
//
// Credit: https://github.com/suitcss/base/

button:focus {
  outline: 1px dotted;
  outline: 5px auto -webkit-focus-ring-color;
}

// 1. Remove the margin in Firefox and Safari

input,
button,
select,
optgroup,
textarea {
  margin: 0;
  font-family: inherit;
  @include font-size(inherit);
  line-height: inherit;
}

// Show the overflow in Edge

button,
input {
  overflow: visible;
}

// Remove the inheritance of text transform in Firefox

button,
select {
  text-transform: none;
}

// Remove the inheritance of word-wrap in Safari.
//
// Details at https://github.com/twbs/bootstrap/issues/24990

select {
  word-wrap: normal;
}

// Remove the dropdown arrow in Chrome from inputs built with datalists.
//
// Source: https://stackoverflow.com/a/54997118

[list]::-webkit-calendar-picker-indicator {
  display: none;
}

// 1. Prevent a WebKit bug where (2) destroys native `audio` and `video`
//    controls in Android 4.
// 2. Correct the inability to style clickable types in iOS and Safari.
// 3. Opinionated: add "hand" cursor to non-disabled button elements.

button,
[type="button"], // 1
[type="reset"],
[type="submit"] {
  -webkit-appearance: button; // 2

  @if $enable-pointer-cursor-for-buttons {
    &:not(:disabled) {
      cursor: pointer; // 3
    }
  }
}


// Remove inner border and padding from Firefox, but don't restore the outline like Normalize.

::-moz-focus-inner {
  padding: 0;
  border-style: none;
}


// Remove the default appearance of temporal inputs to avoid a Mobile Safari
// bug where setting a custom line-height prevents text from being vertically
// centered within the input.
// See https://bugs.webkit.org/show_bug.cgi?id=139848
// and https://github.com/twbs/bootstrap/issues/11266

input[type="date"],
input[type="time"],
input[type="datetime-local"],
input[type="month"] {
  -webkit-appearance: textfield;
}

// 1. Remove the default vertical scrollbar in IE.
// 2. Textareas should really only resize vertically so they don't break their (horizontal) containers.
// 3. Use the same borders as textfields

textarea {
  overflow: auto; // 1
  resize: vertical;  // 2
  -webkit-appearance: textfield; // 3
}

// 1. Browsers set a default `min-width: min-content;` on fieldsets,
//    unlike e.g. `<div>`s, which have `min-width: 0;` by default.
//    So we reset that to ensure fieldsets behave more like a standard block element.
//    See https://github.com/twbs/bootstrap/issues/12359
//    and https://html.spec.whatwg.org/multipage/#the-fieldset-and-legend-elements
// 2. Reset the default outline behavior of fieldsets so they don't affect page layout.

fieldset {
  min-width: 0; // 1
  padding: 0;  // 2
  margin: 0; // 2
  border: 0; // 2
}


// 1. By using `float: left`, the legend will behave like a block element
// 2. Correct the color inheritance from `fieldset` elements in IE.
// 3. Correct the text wrapping in Edge and IE.

legend {
  float: left; // 1
  width: 100%;
  padding: 0;
  margin-bottom: $legend-margin-bottom;
  @include font-size($legend-font-size);
  font-weight: $legend-font-weight;
  line-height: inherit;
  color: inherit; // 2
  white-space: normal; // 3
}


mark {
  padding: $mark-padding;
  background-color: $mark-bg;
}

// Add the correct vertical alignment in Chrome, Firefox, and Opera.

progress {
  vertical-align: baseline;
}


// Fix height of inputs with a type of datetime-local, date, month, week, or time
// See https://github.com/twbs/bootstrap/issues/18842

::-webkit-datetime-edit {
  overflow: visible;
  line-height: 0;
}


// 1. Correct the outline style in Safari.
// 2. This overrides the extra rounded corners on search inputs in iOS so that our
//    `.form-control` class can properly style them. Note that this cannot simply
//    be added to `.form-control` as it's not specific enough. For details, see
//    https://github.com/twbs/bootstrap/issues/11586.

[type="search"] {
  outline-offset: -2px; // 1
  -webkit-appearance: textfield; // 2
}

// Remove the inner padding in Chrome and Safari on macOS.

::-webkit-search-decoration {
  -webkit-appearance: none;
}

// Remove padding around color pickers in webkit browsers

::-webkit-color-swatch-wrapper {
  padding: 0;
}

// 1. Change font properties to `inherit` in Safari.
// 2. Correct the inability to style clickable types in iOS and Safari.

::-webkit-file-upload-button {
  font: inherit; // 1
  -webkit-appearance: button; // 2
}

// Correct element displays

output {
  display: inline-block;
}

// 1. Add the correct display in all browsers

summary {
  display: list-item; // 1
  cursor: pointer;
}

// Add the correct display for template & main in IE 11

template {
  display: none;
}

main {
  display: block;
}

// Always hide an element with the `hidden` HTML attribute.

[hidden] {
  display: none !important;
}