The actual fix to https://github.com/vector-im/riot-web/issues/3175 is this change to `_saveScrollState`, which is to pick the trackedScrollToken based on which node is intersected by the bottom of the scroll panel. This is opposed to the previous logic that picked based on which node was the first from the bottom to be above the bottom of the viewport.
In the case where the viewport bottom does not intersect any events, the topmost event is used.
MatrixChat was trying to display an error if the session failed to
restore, but it was never actually being shown because it was just
set as a member variable and therefore never actually caused
a re-render for the error to be displayed. Almost all errors are
caught by _restoreFromLocalStorage which displays the fancy dialog
if your session can't be restored, so I'm not convinced this ever
even tried to do anything anyway. Remove it.
Specifically:
```
JS 2.1.1 (Linux 0.0.0) joining a room over federation should not get stuck at a spinner FAILED
Did not find exactly one match (found: 0) for componentType:function (props, context, updater) {
```
actually meant that the room directory wasn't displayed - probably because the dispatch `view_room_directory` ended up on another tick of the event loop, meaning that the directory wasn't displayedi. The fix attempted in ths commit is to use `this._setPage` instead to view the directory. This uses `setState` to set the screen to the directory, so I'm not entirely convinced this will solve the problem (as `setState` may also end up doing things on another tick.
and
```
JS 2.1.1 (Linux 0.0.0) loading: MatrixClient rehydrated from stored credentials: shows a room view if we followed a room link FAILED
MatrixChat still not ready after 5 tries
awaitRoomView@/home/travis/build/vector-im/riot-web/test/all-tests.js:201363:90
```
was happening probably because in the handler for the `sync` event in `MatrixChat` (around line 840), there was one case in which the `ready` state may not be true (causing all 5 attempts to fail), and this case relied on `starting_room_alias_payload`. This `starting_room_alias_payload` is now redundant because of `initialScreenAfterLogin`, which was added recently.
Fixes https://github.com/vector-im/riot-web/issues/3529. In the worst case, tsOfNewestEvent will return MAX_SAFE_INTEGER, instead of undefined, as may be the case of some events that were redacted and persisted in indexDB before changes were made to how events are redacted locally. (The important change is that events are now not stripped of their `origin_server_ts`).
Only zero the local notification count when we actually send a
read receipt, otherwise we cause a re-render of the RoomList every
time the user moves the cursor in the window, basically.
As this makes it work out of the box with react-perf chrome
extension (which doesn't do a whole lot other than save you having
to remember the commands, but is still quite nice).
Use an action and force an update when zeroing the number of notifications in a room. This is better than waiting for a `render` to happen at some point. This will hopefully fix https://github.com/vector-im/riot-web/issues/3257
