bootstrap/scss/buttons/_button.scss

@use "sass:color";
@use "../colors" as *;
@use "../config" as *;
@use "../variables" as *;
@use "../functions" as *;
@use "../vendor/rfs" as *;
@use "../mixins/border-radius" as *;
@use "../mixins/box-shadow" as *;
@use "../mixins/focus-ring" as *;
@use "../mixins/gradients" as *;
@use "../mixins/transition" as *;
@use "button-variables" as *;

// Button variants
//
// Easily pump out default styles, as well as :hover, :focus, :active,
// and disabled options for all buttons

// scss-docs-start btn-variant-mixin
@mixin button-variant(
  $background,
  $border,
  $color: color-contrast($background),
  $hover-background: if($color == $color-contrast-light, shade-color($background, $btn-hover-bg-shade-amount), tint-color($background, $btn-hover-bg-tint-amount)),
  $hover-border: if($color == $color-contrast-light, shade-color($border, $btn-hover-border-shade-amount), tint-color($border, $btn-hover-border-tint-amount)),
  $hover-color: color-contrast($hover-background),
  $active-background: if($color == $color-contrast-light, shade-color($background, $btn-active-bg-shade-amount), tint-color($background, $btn-active-bg-tint-amount)),
  $active-border: if($color == $color-contrast-light, shade-color($border, $btn-active-border-shade-amount), tint-color($border, $btn-active-border-tint-amount)),
  $active-color: color-contrast($active-background),
  $disabled-background: $background,
  $disabled-border: $border,
  $disabled-color: color-contrast($disabled-background)
) {
  --#{$prefix}btn-color: #{$color};
  --#{$prefix}btn-bg: #{$background};
  --#{$prefix}btn-border-color: #{$border};
  --#{$prefix}btn-hover-color: #{$hover-color};
  --#{$prefix}btn-hover-bg: #{$hover-background};
  --#{$prefix}btn-hover-border-color: #{$hover-border};
  // --#{$prefix}btn-focus-shadow-rgb: #{to-rgb(color.mix($color, $border, 15%))};
  --#{$prefix}btn-active-color: #{$active-color};
  --#{$prefix}btn-active-bg: #{$active-background};
  --#{$prefix}btn-active-border-color: #{$active-border};
  --#{$prefix}btn-active-shadow: #{$btn-active-box-shadow};
  --#{$prefix}btn-disabled-color: #{$disabled-color};
  --#{$prefix}btn-disabled-bg: #{$disabled-background};
  --#{$prefix}btn-disabled-border-color: #{$disabled-border};
}
// scss-docs-end btn-variant-mixin

// scss-docs-start btn-outline-variant-mixin
@mixin button-outline-variant(
  $color,
  $color-hover: color-contrast($color),
  $active-background: $color,
  $active-border: $color,
  $active-color: color-contrast($active-background)
) {
  --#{$prefix}btn-color: #{$color};
  --#{$prefix}btn-border-color: #{$color};
  --#{$prefix}btn-hover-color: #{$color-hover};
  --#{$prefix}btn-hover-bg: #{$active-background};
  --#{$prefix}btn-hover-border-color: #{$active-border};
  --#{$prefix}btn-focus-shadow-rgb: #{to-rgb($color)};
  --#{$prefix}btn-active-color: #{$active-color};
  --#{$prefix}btn-active-bg: #{$active-background};
  --#{$prefix}btn-active-border-color: #{$active-border};
  --#{$prefix}btn-active-shadow: #{$btn-active-box-shadow};
  --#{$prefix}btn-disabled-color: #{$color};
  --#{$prefix}btn-disabled-bg: transparent;
  --#{$prefix}btn-disabled-border-color: #{$color};
  --#{$prefix}gradient: none;
}
// scss-docs-end btn-outline-variant-mixin

// scss-docs-start btn-size-mixin
@mixin button-size($padding-y, $padding-x, $font-size, $border-radius) {
  --#{$prefix}btn-padding-y: #{$padding-y};
  --#{$prefix}btn-padding-x: #{$padding-x};
  @include rfs($font-size, --#{$prefix}btn-font-size);
  --#{$prefix}btn-border-radius: #{$border-radius};
}
// scss-docs-end btn-size-mixin


//
// Base styles
//

@layer components {
  .btn {
    // scss-docs-start btn-css-vars
    --#{$prefix}btn-padding-x: #{$btn-padding-x};
    --#{$prefix}btn-padding-y: #{$btn-padding-y};
    --#{$prefix}btn-font-family: #{$btn-font-family};
    @include rfs($btn-font-size, --#{$prefix}btn-font-size);
    --#{$prefix}btn-font-weight: #{$btn-font-weight};
    --#{$prefix}btn-line-height: #{$btn-line-height};
    --#{$prefix}btn-color: #{$btn-color};
    --#{$prefix}btn-bg: transparent;
    --#{$prefix}btn-border-width: #{$btn-border-width};
    --#{$prefix}btn-border-color: transparent;
    --#{$prefix}btn-border-radius: #{$btn-border-radius};
    --#{$prefix}btn-hover-border-color: transparent;
    --#{$prefix}btn-box-shadow: #{$btn-box-shadow};
    --#{$prefix}btn-disabled-opacity: #{$btn-disabled-opacity};
    // --#{$prefix}btn-focus-box-shadow: 0 0 0 #{$btn-focus-width} rgba(var(--#{$prefix}btn-focus-shadow-rgb), .5);
    // scss-docs-end btn-css-vars

    display: inline-block;
    padding: var(--#{$prefix}btn-padding-y) var(--#{$prefix}btn-padding-x);
    font-family: var(--#{$prefix}btn-font-family);
    @include font-size(var(--#{$prefix}btn-font-size));
    font-weight: var(--#{$prefix}btn-font-weight);
    line-height: var(--#{$prefix}btn-line-height);
    color: var(--#{$prefix}btn-color);
    text-align: center;
    text-decoration: if($link-decoration == none, null, none);
    white-space: $btn-white-space;
    vertical-align: middle;
    cursor: if($enable-button-pointers, pointer, null);
    user-select: none;
    border: var(--#{$prefix}btn-border-width) solid var(--#{$prefix}btn-border-color);
    @include border-radius(var(--#{$prefix}btn-border-radius));
    @include gradient-bg(var(--#{$prefix}btn-bg));
    @include box-shadow(var(--#{$prefix}btn-box-shadow));
    @include transition($btn-transition);

    &:hover {
      color: var(--#{$prefix}btn-hover-color);
      text-decoration: if($link-hover-decoration == underline, none, null);
      background-color: var(--#{$prefix}btn-hover-bg);
      border-color: var(--#{$prefix}btn-hover-border-color);
    }

    .btn-check + &:hover {
      // override for the checkbox/radio buttons
      color: var(--#{$prefix}btn-color);
      background-color: var(--#{$prefix}btn-bg);
      border-color: var(--#{$prefix}btn-border-color);
    }

    &:focus-visible {
      color: var(--#{$prefix}btn-hover-color);
      @include gradient-bg(var(--#{$prefix}btn-hover-bg));
      border-color: var(--#{$prefix}btn-hover-border-color);
      @include focus-ring(true);
      --#{$prefix}focus-ring-offset: 1px;
    }

    .btn-check:focus-visible + & {
      border-color: var(--#{$prefix}btn-hover-border-color);
      @include focus-ring(true);
    }

    .btn-check:checked + &,
    :not(.btn-check) + &:active,
    &:first-child:active,
    &.active,
    &.show {
      color: var(--#{$prefix}btn-active-color);
      background-color: var(--#{$prefix}btn-active-bg);
      // Remove CSS gradients if they're enabled
      background-image: if($enable-gradients, none, null);
      border-color: var(--#{$prefix}btn-active-border-color);
      @include box-shadow(var(--#{$prefix}btn-active-shadow));

      &:focus-visible {
        @include focus-ring(true);
      }
    }

    .btn-check:checked:focus-visible + & {
      @include focus-ring(true);
    }

    &:disabled,
    &.disabled,
    fieldset:disabled & {
      color: var(--#{$prefix}btn-disabled-color);
      pointer-events: none;
      background-color: var(--#{$prefix}btn-disabled-bg);
      background-image: if($enable-gradients, none, null);
      border-color: var(--#{$prefix}btn-disabled-border-color);
      opacity: var(--#{$prefix}btn-disabled-opacity);
      @include box-shadow(none);
    }
  }


  //
  // Alternate buttons
  //

  // scss-docs-start btn-variant-loops
  @each $color, $value in $theme-colors {
    .btn-#{$color} {
      @if $color == "light" {
        @include button-variant(
          $value,
          $value,
          $hover-background: shade-color($value, $btn-hover-bg-shade-amount),
          $hover-border: shade-color($value, $btn-hover-border-shade-amount),
          $active-background: shade-color($value, $btn-active-bg-shade-amount),
          $active-border: shade-color($value, $btn-active-border-shade-amount)
        );
      } @else if $color == "dark" {
        @include button-variant(
          $value,
          $value,
          $hover-background: tint-color($value, $btn-hover-bg-tint-amount),
          $hover-border: tint-color($value, $btn-hover-border-tint-amount),
          $active-background: tint-color($value, $btn-active-bg-tint-amount),
          $active-border: tint-color($value, $btn-active-border-tint-amount)
        );
      } @else {
        @include button-variant($value, $value);
      }
    }
  }

  @each $color, $value in $theme-colors {
    .btn-outline-#{$color} {
      @include button-outline-variant($value);
    }
  }
  // scss-docs-end btn-variant-loops


  //
  // Link buttons
  //

  // Make a button look and behave like a link
  .btn-link {
    --#{$prefix}btn-font-weight: #{$font-weight-normal};
    --#{$prefix}btn-color: #{$btn-link-color};
    --#{$prefix}btn-bg: transparent;
    --#{$prefix}btn-border-color: transparent;
    --#{$prefix}btn-hover-color: #{$btn-link-hover-color};
    --#{$prefix}btn-hover-border-color: transparent;
    --#{$prefix}btn-active-color: #{$btn-link-hover-color};
    --#{$prefix}btn-active-border-color: transparent;
    --#{$prefix}btn-disabled-color: #{$btn-link-disabled-color};
    --#{$prefix}btn-disabled-border-color: transparent;
    --#{$prefix}btn-box-shadow: 0 0 0 #000; // Can't use `none` as keyword negates all values when used with multiple shadows
    // --#{$prefix}btn-focus-shadow-rgb: #{$btn-link-focus-shadow-rgb};

    text-decoration: $link-decoration;
    @if $enable-gradients {
      background-image: none;
    }

    &:hover,
    &:focus-visible {
      text-decoration: $link-hover-decoration;
    }

    &:focus-visible {
      color: var(--#{$prefix}btn-color);
    }

    &:hover {
      color: var(--#{$prefix}btn-hover-color);
    }

    // No need for an active state here
  }


  //
  // Button Sizes
  //

  .btn-lg {
    @include button-size($btn-padding-y-lg, $btn-padding-x-lg, $btn-font-size-lg, $btn-border-radius-lg);
  }

  .btn-sm {
    @include button-size($btn-padding-y-sm, $btn-padding-x-sm, $btn-font-size-sm, $btn-border-radius-sm);
  }

  .btn-check {
    position: absolute;
    clip: rect(0, 0, 0, 0);
    pointer-events: none;

    &[disabled],
    &:disabled {
      + .btn {
        pointer-events: none;
        filter: none;
        opacity: .65;
      }
    }
  }
}