discourse/app/assets/stylesheets/common/components/buttons.scss

// --------------------------------------------------
// Buttons
// --------------------------------------------------

// Base
// --------------------------------------------------

@mixin btn(
  $text-color: var(--primary),
  $bg-color: var(--primary-low),
  $icon-color: var(--primary-high),
  $hover-text-color: var(--secondary),
  $hover-bg-color: var(--primary-medium),
  $hover-icon-color: var(--primary-low)
) {
  @include form-item-sizing;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin: 0;
  font-weight: normal;
  color: $text-color;
  background: $bg-color;
  cursor: pointer;
  transition: all 0.25s;
  .d-icon {
    color: $icon-color;
    margin-right: 0.45em;
    transition: color 0.25s;
    // For Windows High Contrast (see whcm.scss for more)
    @media (forced-colors: active) {
      color: ButtonText;
    }
  }
  .d-button-label + .d-icon {
    margin-left: 0.45em;
    margin-right: 0;
  }
  &.no-text {
    .d-icon {
      margin-right: 0;
    }
  }
  @include hover {
    background: $hover-bg-color;
    color: $hover-text-color;
    .d-icon {
      color: $hover-icon-color;
      // For Windows High Contrast (see whcm.scss for more)
      @media (forced-colors: active) {
        color: Highlight;
      }
    }
  }
  &:focus {
    outline: none;
    background: $hover-bg-color;
    color: $hover-text-color;
    .d-icon {
      color: $hover-icon-color;
      @media (forced-colors: active) {
        color: Highlight;
      }
    }
  }
  &[href] {
    color: $text-color;
  }
  &:active,
  &.btn-active {
    @include linear-gradient($hover-bg-color 0%, $bg-color 100%);
    border-bottom-color: $bg-color;
  }
  &[disabled],
  &.disabled {
    &:not(.is-loading) {
      opacity: 0.4;
    }
    &:hover {
      color: $text-color;
      background: $bg-color;
      .d-icon {
        color: $icon-color;
      }
    }
    cursor: not-allowed;
  }

  .loading-container {
    display: none;
    margin: 0 6.75px 0 0;
  }

  &.is-loading {
    &.btn-text {
      .d-button-label {
        font-size: var(--font-down-2);
      }

      &.btn-small {
        .loading-icon {
          font-size: var(--font-down-1);
          margin-right: 0.2em;
        }
      }
    }

    .loading-icon {
      animation: rotate-forever 1s infinite linear, fadein 1s;
    }
  }
}

.btn.hidden {
  display: none;
}

// Default button
// --------------------------------------------------

.btn {
  @include btn;
}

// Primary button
// --------------------------------------------------

.btn-primary {
  @include btn(
    $text-color: var(--secondary),
    $bg-color: var(--tertiary),
    $icon-color: var(--secondary),
    $hover-bg-color: var(--tertiary-hover),
    $hover-icon-color: var(--secondary)
  );
}

// Danger button
// --------------------------------------------------

.btn-danger {
  @include btn(
    $text-color: var(--secondary),
    $bg-color: var(--danger),
    $icon-color: var(--danger-low),
    $hover-bg-color: var(--danger-hover),
    $hover-icon-color: var(--danger-low)
  );
}

// ✘ and ✔ buttons
// --------------------------------------------------

.btn.cancel {
  @include btn(
    $text-color: var(--secondary),
    $bg-color: var(--danger),
    $icon-color: var(--secondary),
    $hover-bg-color: var(--danger-hover),
    $hover-icon-color: var(--secondary)
  );
}

.btn.ok {
  @include btn(
    $text-color: var(--secondary),
    $bg-color: var(--success),
    $icon-color: var(--secondary),
    $hover-bg-color: var(--success-hover),
    $hover-icon-color: var(--secondary)
  );
}

// Social buttons
// --------------------------------------------------

.btn-social {
  color: #000;
  background: #fff;
  border: 1px solid transparent;
  &:hover,
  &:focus {
    box-shadow: shadow("card");
    outline: 1px solid #000;
  }
  &[href] {
    color: var(--secondary);
  }
  &:before {
    margin-right: 9px;
    font-size: var(--font-0);
  }
  .d-icon,
  &.btn:hover .d-icon {
    color: #000;
  }
  &.google_oauth2 {
    background: var(--google);
    color: #333;
    // non-FA SVG icon for Google in login-buttons.hbs
    .d-icon {
      opacity: 0.9;
    }
    &:hover,
    &:focus {
      color: currentColor;
    }
  }

  &.cas {
    .d-icon {
      color: var(--cas);
    }
    &:hover {
      .d-icon {
        color: var(--cas);
      }
    }
  }
  &.twitter {
    .d-icon {
      color: var(--twitter);
    }
    &:hover {
      .d-icon {
        color: var(--twitter);
      }
    }
  }
  &.github {
    .d-icon {
      color: var(--github);
    }
    &:hover {
      .d-icon {
        color: var(--github);
      }
    }
  }
  &.discord {
    .d-icon {
      color: var(--discord);
    }
    &:hover {
      .d-icon {
        color: var(--discord);
      }
    }
  }
}

// Button Sizes
// --------------------------------------------------

// Small

.btn-small {
  font-size: var(--font-down-1);
  min-height: 20px;
}

// Large

.btn-large {
  font-size: var(--font-up-1);
}

// Bonus Buttons
// --------------------------------------------------

.btn-flat {
  background: transparent;
  border: 0;
  line-height: var(--line-height-small);
  transition: color 0.25s, background 0.25s;
  .d-icon {
    color: var(--primary-low-mid);
  }
  @include hover {
    background: transparent;
    color: var(--primary);
    .d-icon {
      color: var(--primary);
    }
  }
  &.close {
    padding: 0;
    background: transparent;
    font-size: var(--font-up-3);
    .d-icon {
      color: var(--primary-high);
    }
    @include hover {
      background: transparent;
      .d-icon {
        color: var(--primary);
      }
    }
  }
  &.btn-text {
    color: var(--tertiary);
    &[disabled] {
      &,
      &:hover,
      &.btn-hover,
      &:focus {
        color: var(--primary);
      }
    }
    &:not([disabled]) {
      &:hover,
      &.btn-hover,
      &:focus {
        color: var(--tertiary-hover);
      }

      &:active,
      &.btn-active {
        @include linear-gradient(
          var(--primary-low-mid) 0%,
          var(--primary-very-low) 100%
        );
      }
    }
  }
  &:focus {
    outline: none;
    background: var(--primary-low);
    .d-icon {
      color: var(--primary);
    }
  }
}

.btn-link {
  background: transparent;
  border: 0;
  padding: 0;
  color: var(--tertiary);
}

.btn-mini-toggle {
  padding: 0.4em 0.467em;
  .d-icon {
    color: var(--primary-high);
  }
  @include hover {
    background: transparent;
    .d-icon {
      color: var(--primary);
    }
  }
  &:focus {
    background: var(--primary-low);
    .d-icon {
      color: var(--primary);
    }
  }
}