chinwagsocial/app/javascript/mastodon/reducers/statuses.js
Matt Panaro 31f7c3fc5d Summary: fix slowness due to layout thrashing when reloading a large … (#12661)
* 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
2019-12-29 05:39:48 +01:00

84 lines
2.9 KiB
JavaScript

import {
REBLOG_REQUEST,
REBLOG_FAIL,
FAVOURITE_REQUEST,
FAVOURITE_FAIL,
UNFAVOURITE_SUCCESS,
BOOKMARK_REQUEST,
BOOKMARK_FAIL,
} from '../actions/interactions';
import {
STATUS_MUTE_SUCCESS,
STATUS_UNMUTE_SUCCESS,
STATUS_REVEAL,
STATUS_HIDE,
STATUS_COLLAPSE,
} from '../actions/statuses';
import { TIMELINE_DELETE } from '../actions/timelines';
import { STATUS_IMPORT, STATUSES_IMPORT } from '../actions/importer';
import { Map as ImmutableMap, fromJS } from 'immutable';
const importStatus = (state, status) => state.set(status.id, fromJS(status));
const importStatuses = (state, statuses) =>
state.withMutations(mutable => statuses.forEach(status => importStatus(mutable, status)));
const deleteStatus = (state, id, references) => {
references.forEach(ref => {
state = deleteStatus(state, ref[0], []);
});
return state.delete(id);
};
const initialState = ImmutableMap();
export default function statuses(state = initialState, action) {
switch(action.type) {
case STATUS_IMPORT:
return importStatus(state, action.status);
case STATUSES_IMPORT:
return importStatuses(state, action.statuses);
case FAVOURITE_REQUEST:
return state.setIn([action.status.get('id'), 'favourited'], true);
case UNFAVOURITE_SUCCESS:
const favouritesCount = action.status.get('favourites_count');
return state.setIn([action.status.get('id'), 'favourites_count'], favouritesCount - 1);
case FAVOURITE_FAIL:
return state.get(action.status.get('id')) === undefined ? state : state.setIn([action.status.get('id'), 'favourited'], false);
case BOOKMARK_REQUEST:
return state.get(action.status.get('id')) === undefined ? state : state.setIn([action.status.get('id'), 'bookmarked'], true);
case BOOKMARK_FAIL:
return state.get(action.status.get('id')) === undefined ? state : state.setIn([action.status.get('id'), 'bookmarked'], false);
case REBLOG_REQUEST:
return state.setIn([action.status.get('id'), 'reblogged'], true);
case REBLOG_FAIL:
return state.get(action.status.get('id')) === undefined ? state : state.setIn([action.status.get('id'), 'reblogged'], false);
case STATUS_MUTE_SUCCESS:
return state.setIn([action.id, 'muted'], true);
case STATUS_UNMUTE_SUCCESS:
return state.setIn([action.id, 'muted'], false);
case STATUS_REVEAL:
return state.withMutations(map => {
action.ids.forEach(id => {
if (!(state.get(id) === undefined)) {
map.setIn([id, 'hidden'], false);
}
});
});
case STATUS_HIDE:
return state.withMutations(map => {
action.ids.forEach(id => {
if (!(state.get(id) === undefined)) {
map.setIn([id, 'hidden'], true);
}
});
});
case STATUS_COLLAPSE:
return state.setIn([action.id, 'collapsed'], action.isCollapsed);
case TIMELINE_DELETE:
return deleteStatus(state, action.id, action.references);
default:
return state;
}
};