Allow customizing the focus element per fragment rule

[daun]

Describe the problem

• Most fragment visits don't require setting focus to the main element on navigation
• Especially filter UIs should either not move focus or move it to the updated list which won't be a main element

Describe the proposed solution

• I'd suggest adding a focus option to fragment rules that is passed into the new visit.a11y.focus option, if present
• Should fragment visits be false here by default? Or better to make people be explicit?

How important is this feature to you?

• [ ] Nice to have
• [x] Would make the life of screen-reader users a lot easier
• [ ] I cannot use swup without it

[hirasso]

Since a11y plugin is optional, the focus flag should be optional, as well. So a default value of false sounds good to me!

[daun]

@hirasso If I'm correct, the current behavior of a11y + fragment plugins is to move the focus to the main element, even after fragment visits. A default value of false would mean not moving focus, so a breaking change.

[hirasso]

Ah! Right. What would you prefer?

[daun]

An optional focus key with a default of null sounds good. The current behaviour seems to me like a good default solution, i.e. focus the main element as configured by the a11y plugin. That's already a better experience for keyboard users than traditional MPAs that return focus to the top of the document on each navigation — here we're already skipping the header and jumping right to the content.

Depending on the markup of your fragments, this could well be enough, assuming the new fragment is a main tag and comes first in the document. For other cases like filter UIs, specifically setting or disabling a new focus option on the fragment rules would be a great way for fine-tuning this.

[hirasso]

Great, let's go with a default of undefined then, just like with the rule option for name!