Overleaf/services/web/frontend/stylesheets/bootstrap-5/components/form.scss

.form-check-input {
  @function form-check-box-svg($color) {
    @return url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'><path fill='none' stroke='#{$color}' stroke-linecap='round' stroke-linejoin='round' stroke-width='3' d='m6 10 3 3 6-6'/></svg>");
  }
  @function form-check-radio-svg($color) {
    @return url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='-4 -4 8 8'><circle r='2' fill='#{$color}'/></svg>");
  }
  @function form-check-indeterminate-svg($color) {
    @return url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'><path fill='none' stroke='#{$color}' stroke-linecap='round' stroke-linejoin='round' stroke-width='3' d='M6 10h8'/></svg>");
  }

  &:hover {
    &:not(:disabled) {
      border-color: var(--border-hover);

      &:checked,
      &[type='checkbox']:indeterminate {
        background-color: var(--bg-accent-02);
        border-color: var(--bg-accent-02);
      }
    }
  }

  &:disabled {
    @mixin input-disabled-styles {
      background-color: $input-disabled-bg;
      border-color: $input-disabled-border-color;
    }

    @include input-disabled-styles;

    &[type='checkbox']:indeterminate {
      @include input-disabled-styles;

      background-image: escape-svg(form-check-indeterminate-svg($neutral-40));
    }
  }

  // Use disabled attribute in addition of :disabled pseudo-class
  // See: https://github.com/twbs/bootstrap/issues/28247
  &[disabled],
  &:disabled {
    ~ .form-check-label {
      color: $input-disabled-color;
    }

    &:checked {
      &[type='checkbox'] {
        background-image: escape-svg(form-check-box-svg($neutral-40));
      }

      &[type='radio'] {
        background-image: escape-svg(form-check-radio-svg($neutral-40));
      }
    }
  }
}

.form-control {
  &[disabled],
  &:disabled {
    &::placeholder {
      color: var(--content-disabled);
    }
  }
}

.form-text {
  display: inline-flex;
  gap: $spacing-02;
  line-height: var(--line-height-02);

  .form-control[disabled] ~ & {
    color: var(--content-disabled);
  }
}

.form-label {
  &:has(+ .form-control[disabled]) {
    color: var(--content-disabled);
  }
}