Feature

Description

This PR addresses an optimization regarding the number of requests that Updatable possibly makes.

The rationale is this: it doesn't really make sense to keep elements that aren't visible up to date. this can be deferred, which defaults to lazy loading.

We have to distinguish 3 cases here:

• is visible - behavior as usual
• is not visible - ignore requests. Basically shouldUpdate == false
• transition from invisible to visible - pull and morph once, then listen as normal

Implementation

I leaned on Turbo's solution here a bit, and introduced a separate AppearanceObserver. The thing I added to the regular IntersectionObserver is an observer for document.visibilityState. This means:

• not only hidden elements in the DOM tree of the opened browser tab
• but also generally elements that are in browser tabs that are currently closed/hidden

will not trigger updates. When they come into view, e.g. by scrolling into the viewport, or switching browser tabs, they will perform a one-time update and then continue listening as normal.

In terms of view helpers, I only added an observe_appearance flag to keep this optional. The element will then observe both behaviors though.

• My code follows the style guidelines of this project
• Checks (StandardRB & Prettier-Standard) are passing