Show the back end header on scroll-up

[leofeyer]

Thank you @ausi (see https://codepen.io/ausi/pen/rNPrmGX).

[ausi]

Just for the record: I’m not a huge fan of these show-on-scroll-up fixed headers. I’d prefer keeping it fixed all the time.

[aschempp]

see leofeyer#9 for a more universal Stimulus solution. The advantages are

1. it can be applied to any element, not just the <header>.
2. it would correctly handle the <header> element being replaced on the page (e.g. through a Turbo frame request)
3. It doesn't fail if there is another <header> on the page (e.g. inside a <section> of some content)
4. it can be reused to add a scroll-up class, e.g. for a "back to top link" later on
5. it would also be easy to add a user permission later on. Just skip the data attributes in the controller to disable it (contrary to a globally loaded script).

[leofeyer]

Just for the record: I’m not a huge fan of these show-on-scroll-up fixed headers. I’d prefer keeping it fixed all the time.

I know. But in the survey, only 14 people voted for a sticky header and 42 people voted against it. Therefore, the default behavior should be a non-sticky header.

[aschempp]

This would make sure the is always a threshold value, even if the data attribute is not set. We could also set the default to 40 and omit it in our template if that's a sane default.