Missing preferences for scroll/paginated affordances

[JayPanoz]

In preferences, we have an affordances object that accepts configuration for scroll and paginated (reflow and fxl, no webPub yet)

To be consistent, these affordances are currently missing:

• toggleOnMiddlePointer for paginated. This allows you toggle immersive mode on tap|click and already exists for scroll. Having navigation arrows be discardable and hintable through immersive mode makes it kinda obvious it is missing because you cannot set it in the first place and don’t necessarily know what the app is doing (enabled for tap)
• in scroll, we can hideOnForwardScroll and showOnBackwardScroll but we do not have any way to enable/disable auto-showing when reaching the top and bottom of the document. So again, the app is doing something you may not be aware of and cannot control
• contextualization of scroll affordances a.k.a previous/next links based on breakpoints (edit)

We could also wonder whether scroll affordances should be revamped to respect the default + breakpoint pattern we are enforcing pretty much anywhere else, for each supported profile (that is reflow and webpub in that case). Currently they are just global.

[HadrienGardeur]

in scroll, we can hideOnForwardScroll and showOnBackwardScroll but we do not have any way to enable/disable auto-showing when reaching the top and bottom of the document. So again, the app is doing something you may not be aware of and cannot control

We might be giving people a footgun if they combine a number of these properties together.
Let's say that we set things to:

• hide on forward scroll
• do not show on backward scroll
• and do not show on top/bottom

I could end up with a UI that hides itself when scrolling down and can never be displayed again.

[JayPanoz]

Yeah that is one of my worries as you may guess, and there probably are footguns elsewhere while I'm thinking about this, due to all the combinations possible for some settings. As demonstrated with the navigation arrows, there were some corner cases slipping through the cracks that I had to cover in a quick update. And layered that is never discarded is an obvious footgun for instance, because it will cover the contents on smaller screens.

Maybe at some point we should take time to review some preferences to see whether that's the case, and how to handle them, especially as we already validate some things on creation, and warn if we spot an issue – at least for critical preferences e.g. actions.

Not sure what's best when some combinations are perfectly fine and others are not, and whether that warrants validation with a warning, or a redesign of the preference, but at least there can be some policy we can follow and point to when needed.

I guess issues will become more obvious once more people could use these preferences more extensively. And if there are issues at all or if they aren't even used because our default makes the most sense. That could also help spotting if we went overboard and could have just provided global strategies instead of several properties you can set very precisely for some features – which also makes the job more difficult for us in the sense this is additional complexity.

[JayPanoz]

We're also missing a pref to contextualize scroll affordances based on breakpoint (Previous/Next vs context) so I'll have to introduce breakpoints into the pref for scroll.