Allow default scrolling behavior on fragment visits

[daun]

Describe the problem

• Currently, the plugin will disable the scroll reset for any fragment visit
• There's certain scenarios where you'd still want the default scroll behavior: pagination or filters below the content

Describe the proposed solution

• Add a scroll option to fragment rules

Alternatives considered

• Hooking after the plugin and manually setting visit.scroll.reset = true;
• It's preferable to have an official API as it might be quite a common thing for people to try to achieve

How important is this feature to you?

• [ ] Nice to have
• [x] Would make my life a lot easier
• [ ] I cannot use swup without it

[hirasso]

Great idea! And should be easily achievable. Another name for the rule option could preserveScroll with a default of true, to keep defaults to positive values.

[daun]

What about allowing a fragment id #list as a value of the scroll option? Some fragment visits might require scrolling to a specific element, e.g. the result list of a filter UI.

[hirasso]

Interesting idea! But I feel like we should leave this to the implementors. With the simplification of the fragmentVisit object it would now be very simple to implement custom logic:

swup.hooks.on('content:replace', async (visit) => {
  if (visit.fragmentVisit?.name === 'my-fragment-visit') {
    visit.scroll.reset = true;
  }
});

or

swup.hooks.on('content:replace', async (visit) => {
  if (visit.fragmentVisit?.name === 'my-fragment-visit') {
    visit.scroll.target = '#list';
  }
});

Do you think we still need this as a rule option then?

[hirasso]

If we go with a new rule option, is this what you were imagining?

{
  scroll: boolean | string
}

Where scroll would be false for each rule if not customized. Options would be

1. scroll to the top if the rule matches:

{
  scroll: true
}

2. scroll to the first matching element if the rule matches:

{
  scroll: '#list'
}

I actually like this a lot, will create a PR.