feat(sync/v3): Remove TL size config option in favor of using the sync filter

src/api/client/sync/v3/joined.rs

@@ -38,7 +38,7 @@ use super::{load_timeline, share_encrypted_room};
 use crate::client::{
 	ignored_filter,
 	sync::v3::{
-		DeviceListUpdates, SyncContext, prepare_lazily_loaded_members,
+		DEFAULT_TIMELINE_LIMIT, DeviceListUpdates, SyncContext, prepare_lazily_loaded_members,
 		state::{build_state_incremental, build_state_initial},
 	},
 };
@@ -63,6 +63,7 @@ pub(super) async fn load_joined_room(
 		last_sync_end_count,
 		current_count,
 		full_state,
+		filter,
 		..
 	} = sync_context;
 	let mut device_list_updates = DeviceListUpdates::new();
@@ -92,6 +93,16 @@ pub(super) async fn load_joined_room(
 		try_join(current_shortstatehash, last_sync_end_shortstatehash).await?;
 
 	// load recent timeline events.
+	// if the filter specifies a limit, that will be used, otherwise
+	// `DEFAULT_TIMELINE_LIMIT` will be used. `DEFAULT_TIMELINE_LIMIT` will also be
+	// used if the limit is somehow greater than usize::MAX.
+
+	let timeline_limit = filter
+		.room
+		.timeline
+		.limit
+		.and_then(|limit| limit.try_into().ok())
+		.unwrap_or(DEFAULT_TIMELINE_LIMIT);
 
 	let timeline = load_timeline(
 		services,
@@ -99,7 +110,7 @@ pub(super) async fn load_joined_room(
 		room_id,
 		last_sync_end_count.map(PduCount::Normal),
 		Some(PduCount::Normal(current_count)),
-		services.config.incremental_sync_max_timeline_size,
+		timeline_limit,
 	);
 
 	let receipt_events = services

src/api/client/sync/v3/left.rs

@@ -21,7 +21,10 @@ use crate::client::{
 	TimelinePdus, ignored_filter,
 	sync::{
 		load_timeline,
-		v3::{SyncContext, prepare_lazily_loaded_members, state::build_state_initial},
+		v3::{
+			DEFAULT_TIMELINE_LIMIT, SyncContext, prepare_lazily_loaded_members,
+			state::build_state_initial,
+		},
 	},
 };
 
@@ -148,19 +151,29 @@ pub(super) async fn load_left_room(
 							.await?
 							.saturating_sub(1)
 					};
+
+					// end the timeline at the user's leave event
 					let timeline_end_count = services
 						.rooms
 						.timeline
 						.get_pdu_count(leave_pdu.event_id())
 						.await?;
 
+					// limit the timeline using the same logic as for joined rooms
+					let timeline_limit = filter
+						.room
+						.timeline
+						.limit
+						.and_then(|limit| limit.try_into().ok())
+						.unwrap_or(DEFAULT_TIMELINE_LIMIT);
+
 					let timeline = load_timeline(
 						services,
 						syncing_user,
 						room_id,
 						Some(timeline_start_count),
 						Some(timeline_end_count),
-						services.config.incremental_sync_max_timeline_size,
+						timeline_limit,
 					)
 					.await?;
 

src/api/client/sync/v3/mod.rs

@@ -52,6 +52,11 @@ use crate::{
 	},
 };
 
+/// The default maximum number of events to return in the `timeline` key of
+/// joined and left rooms. If the number of events sent since the last sync
+/// exceeds this number, the `timeline` will be `limited`.
+const DEFAULT_TIMELINE_LIMIT: usize = 30;
+
 /// A collection of updates to users' device lists, used for E2EE.
 struct DeviceListUpdates {
 	changed: HashSet<OwnedUserId>,