Bootstrap: Expand `position-fixed` into responsive, ie `position-fixed-lg-up`

[aojes]

I dug around an hour, sure I'd find this, tho i didn't. It is small, tho it would help responsive layout. In my case, I have a nav sidebar, fixed when 'lg' and 'sm', but i need to make it display as block on tablets and phones.
Thank you.

<header class="position-fixed[-md-up|-md-lg-xl]">
  <nav>
  </nav>
</header>

[muuvmuuv]

To get it more into Bootstrap philosophy I would more likely do p-[breakpoint]-[value], see Display Property.

_utilities/_position.scss_:

$positions: static, relative, absolute, fixed, sticky;

@each $breakpoint in map-keys($grid-breakpoints) {
  @include media-breakpoint-up($breakpoint) {
    $infix: breakpoint-infix($breakpoint, $grid-breakpoints);

    @each $value in $positions {
      .p#{$infix}-#{$value} {
        position: $value !important;
      }
    }
  }
}

[MartijnCuppens]

In v5 you will be able to use our build in utility API:

$utilities: (
  "position": (
      property: position,
      responsive: true,
      values: static relative absolute fixed sticky
  ),
);

Which will generate classes like .position-md-fixed or .position-sm-relative.