* Revert "persist last-intersected status update and restore when ScrollableList is restored"
This reverts commit 07e26142ef6a8e74bd2ac5e9b461a5a1699bd4c8.
accidentally merged spurious code in https://github.com/tootsuite/mastodon/pull/12661. https://github.com/tootsuite/mastodon/pull/12735 removes the slowdown that this code was trying to solve; and other functionality successfully restores the view state of the list
* Revert "cache currently-viewing status id to avoid calling redux with identical value"
This reverts commit c93df2159fbd3888a5c48d8a8b8ae61dbbc54b89.
accidentally merged spurious code in https://github.com/tootsuite/mastodon/pull/12661. https://github.com/tootsuite/mastodon/pull/12735 removes the slowdown that this code was trying to solve; and other functionality successfully restores the view state of the list
* Summary: fix slowness due to layout thrashing when reloading a large set of status updates
in order to limit the maximum size of a status in a list view (e.g. the home timeline), so as to avoid having to scroll all the way through an abnormally large status update (see https://github.com/tootsuite/mastodon/pull/8205), the following steps are taken:
•the element containing the status is rendered in the browser
•its height is calculated, to determine if it exceeds the maximum height threshold.
Unfortunately for performance, these steps are carried out in the componentDidMount(/Update) method, which also performs style modifications on the element. The combination of height request and style modification during javascript evaluation in the browser leads to layout-thrashing, where the elements are repeatedly re-laid-out (see https://developers.google.com/web/fundamentals/performance/rendering/avoid-large-complex-layouts-and-layout-thrashing & https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Performance_best_practices_for_Firefox_fe_engineers).
The solution implemented here is to memoize the collapsed state in Redux the first time the status is seen (e.g. when fetched as part of a small batch, to populate the home timeline) , so that on subsequent re-renders, the value can be queried, rather than recalculated. This strategy is derived from https://github.com/tootsuite/mastodon/pull/4439 & https://github.com/tootsuite/mastodon/pull/4909, and should resolve https://github.com/tootsuite/mastodon/issues/12455.
Andrew Lin (https://github.com/onethreeseven) is thanked for his assistance in root cause analysis and solution brainstorming
* remove getSnapshotBeforeUpdate from status
* remove componentWillUnmount from status
* persist last-intersected status update and restore when ScrollableList is restored
e.g. when navigating from home-timeline to a status conversational thread and <Back again
* cache currently-viewing status id to avoid calling redux with identical value
* refactor collapse toggle to pass explicit boolean
IntersectionObserverArticle is made to save on RAM by avoiding fully rendering
items that are far out of view. However, it did not work for items spawned
outside the intersection observer.
