`bump_stamp` corresponds to the `stream_ordering` of the latest `DEFAULT_BUMP_EVENT_TYPES` in the room. This helps clients sort more readily without them needing to pull in a bunch of the timeline to determine the last activity. `bump_event_types` is a thing because for example, we don't want display name changes to mark the room as unread and bump it to the top. For encrypted rooms, we just have to consider any activity as a bump because we can't see the content and the client has to figure it out for themselves.
Outside of Synapse, `bump_stamp` is just a free-form counter so other implementations could use `received_ts`or `origin_server_ts` (see the [*Security considerations* section in MSC3575 about the potential pitfalls of using `origin_server_ts`](https://github.com/matrix-org/matrix-spec-proposals/blob/kegan/sync-v3/proposals/3575-sync.md#security-considerations)). It doesn't have any guarantee about always going up. In the Synapse case, it could go down if an event was redacted/removed (or purged in cases of retention policies).
In the future, we could add `bump_event_types` as [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) mentions if people need to customize the event types.
---
In the Sliding Sync proxy, a similar [`timestamp` field was added](https://github.com/matrix-org/sliding-sync/pull/247) for the same purpose but the name is not obvious what it pertains to or what it's for.
The `timestamp` field was also added to Ruma in https://github.com/ruma/ruma/pull/1622
Sort is no longer configurable and we always sort rooms by the `stream_ordering` of the last event in the room or the point where the user can see up to in cases of leave/ban/invite/knock.
Spawning from https://github.com/element-hq/synapse/pull/17187#discussion_r1619492779 around wanting to put `SlidingSyncBody` (parse the request in the rest layer), `SlidingSyncConfig` (from the rest layer, pass to the handler), `SlidingSyncResponse` (pass the response from the handler back to the rest layer to respond) somewhere that doesn't contaminate the imports and cause circular import issues.
- Moved Pydantic parsing models to `synapse/types/rest`
- Moved handler types to `synapse/types/handlers`
Based on [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): Sliding Sync
This iteration only focuses on returning the list of room IDs in the sliding window API (without sorting/filtering).
Rooms appear in the Sliding sync response based on:
- `invite`, `join`, `knock`, `ban` membership events
- Kicks (`leave` membership events where `sender` is different from the `user_id`/`state_key`)
- `newly_left` (rooms that were left during the given token range, > `from_token` and <= `to_token`)
- In order for bans/kicks to not show up, you need to `/forget` those rooms. This doesn't modify the event itself though and only adds the `forgotten` flag to `room_memberships` in Synapse. There isn't a way to tell when a room was forgotten at the moment so we can't factor it into the from/to range.
### Example request
`POST http://localhost:8008/_matrix/client/unstable/org.matrix.msc3575/sync`
```json
{
"lists": {
"foo-list": {
"ranges": [ [0, 99] ],
"sort": [ "by_notification_level", "by_recency", "by_name" ],
"required_state": [
["m.room.join_rules", ""],
["m.room.history_visibility", ""],
["m.space.child", "*"]
],
"timeline_limit": 100
}
}
}
```
Response:
```json
{
"next_pos": "s58_224_0_13_10_1_1_16_0_1",
"lists": {
"foo-list": {
"count": 1,
"ops": [
{
"op": "SYNC",
"range": [0, 99],
"room_ids": [
"!MmgikIyFzsuvtnbvVG:my.synapse.linux.server"
]
}
]
}
},
"rooms": {},
"extensions": {}
}
```
