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Fix room history not being visible even if we have historical keys #8563

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May 11, 2022
Merged

Fix room history not being visible even if we have historical keys #8563

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33092f1
Fix room history not being visible even if we have historical keys
SimonBrandner May 11, 2022
cebd65b
Throttle `recheckFirstVisibleEventIndex()`
SimonBrandner May 11, 2022
8792fcd
Move `recheckFirstVisibleEventIndex()` out of `onEventDecrypted()`
SimonBrandner May 11, 2022
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21 changes: 16 additions & 5 deletions src/components/structures/TimelinePanel.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ import { TimelineWindow } from "matrix-js-sdk/src/timeline-window";
import { EventType, RelationType } from 'matrix-js-sdk/src/@types/event';
import { SyncState } from 'matrix-js-sdk/src/sync';
import { RoomMember, RoomMemberEvent } from 'matrix-js-sdk/src/models/room-member';
import { debounce } from 'lodash';
import { debounce, throttle } from 'lodash';
import { logger } from "matrix-js-sdk/src/logger";
import { ClientEvent } from "matrix-js-sdk/src/client";
import { Thread } from 'matrix-js-sdk/src/models/thread';
Expand Down Expand Up @@ -806,23 +806,34 @@ class TimelinePanel extends React.Component<IProps, IState> {
// Can be null for the notification timeline, etc.
if (!this.props.timelineSet.room) return;

if (ev.getRoomId() !== this.props.timelineSet.room.roomId) return;

if (!this.state.events.includes(ev)) return;

this.recheckFirstVisibleEventIndex();

// Need to update as we don't display event tiles for events that
// haven't yet been decrypted. The event will have just been updated
// in place so we just need to re-render.
// TODO: We should restrict this to only events in our timeline,
// but possibly the event tile itself should just update when this
// happens to save us re-rendering the whole timeline.
if (ev.getRoomId() === this.props.timelineSet.room.roomId) {
this.buildCallEventGroupers(this.state.events);
this.forceUpdate();
}
this.buildCallEventGroupers(this.state.events);
this.forceUpdate();
};
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I'm curious how this fixes element-hq/element-web#16983

What stopped it from working before?

What changes were made to make history visible now?

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@t3chguy t3chguy May 11, 2022 •
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We weren't re-checking checkForPreJoinUISI when we decrypted events, there's a comment in checkForPreJoinUISI which says it treats on-going decryptions the same as failed decryptions. This created a race condition between rendering and decryption. So if you receive keys after the initial render, its almost guaranteed to go down the unhappy path.

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This specific bit doesn't do it; the recheck method does the trick - now when an event is decrypted we check if we can show older events, we didn't do that before

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Beat me to it (again today :D)

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@MadLittleMods MadLittleMods May 11, 2022 •
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Is it possible to write a test for this scenario so we don't regress? This stuff seems very order dependent and tricky to get right

How were you testing locally to confirm the change works? (reproduction steps)

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@t3chguy t3chguy May 11, 2022 •
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We can regression test the single edge we identified and fixed here, but there are so many edges, you will struggle to cover them all. Even hitting 100% coverage won't cover all the possible races & scenarios.

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I think it should be possible - I'll have a look into it, would you mind creating an issue?

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element-hq/element-web#22155 ⏩


private onSync = (clientSyncState: SyncState, prevState: SyncState, data: object): void => {
if (this.unmounted) return;
this.setState({ clientSyncState });
};

private recheckFirstVisibleEventIndex = throttle((): void => {
const firstVisibleEventIndex = this.checkForPreJoinUISI(this.state.events);
if (firstVisibleEventIndex !== this.state.firstVisibleEventIndex) {
this.setState({ firstVisibleEventIndex });
}
}, 500, { leading: true, trailing: true });

private readMarkerTimeout(readMarkerPosition: number): number {
return readMarkerPosition === 0 ?
this.context?.readMarkerInViewThresholdMs ?? this.state.readMarkerInViewThresholdMs :
Expand Down