Use a recursive clear when removing a container or space view

crates/viewer/re_viewer_context/src/store_hub.rs

@@ -711,8 +711,9 @@ impl StoreHub {
                 }
 
                 let store_events = blueprint.gc(&GarbageCollectionOptions {
+                    // TODO(#8249): configure blueprint GC to remove an entity if all that remains of it is a recursive clear
                     target: GarbageCollectionTarget::Everything,
-                    protect_latest: 0,
+                    protect_latest: 1, // keep the latest instance of everything, or we will forget things that haven't changed in a while
                     time_budget: re_entity_db::DEFAULT_GC_TIME_BUDGET,
                     protected_time_ranges,
                 });

crates/viewer/re_viewer_context/src/undo.rs

@@ -78,14 +78,15 @@ impl BlueprintUndoState {
         }
     }
 
+    /// Clears the "redo buffer".
     pub fn clear_redo(&mut self, blueprint_db: &mut EntityDb) {
         re_tracing::profile_function!();
 
         if let Some(last_kept_event_time) = self.current_time.take() {
             let first_dropped_event_time =
                 TimeInt::new_temporal(last_kept_event_time.as_i64().saturating_add(1));
 
-            // Drop everything before the current timeline time
+            // Drop everything after the current timeline time
             blueprint_db.drop_time_range(
                 &blueprint_timeline(),
                 ResolvedTimeRange::new(first_dropped_event_time, re_chunk::TimeInt::MAX),

crates/viewer/re_viewport_blueprint/src/container.rs

@@ -375,11 +375,24 @@ impl ContainerBlueprint {
 
     /// Clears the blueprint component for this container.
     pub fn clear(&self, ctx: &ViewerContext<'_>) {
-        // TODO: ecursive clear
-        ctx.command_sender.send_system(SystemCommand::DropEntity(
-            ctx.store_context.blueprint.store_id().clone(),
-            self.entity_path(),
-        ));
+        // We can't delete the entity, because we need to support undo.
+        // TODO(#8249): configure blueprint GC to remove this entity if all that remains is the recursive clear.
+        let timepoint = ctx.store_context.blueprint_timepoint_for_writes();
+
+        let chunk = Chunk::builder(self.entity_path())
+            .with_archetype(
+                RowId::new(),
+                timepoint.clone(),
+                &re_types::archetypes::Clear::recursive(),
+            )
+            .build()
+            .unwrap();
+
+        ctx.command_sender
+            .send_system(SystemCommand::UpdateBlueprint(
+                ctx.store_context.blueprint.store_id().clone(),
+                vec![chunk],
+            ));
     }
 
     pub fn to_tile(&self) -> egui_tiles::Tile<SpaceViewId> {

crates/viewer/re_viewport_blueprint/src/space_view.rs

@@ -310,11 +310,24 @@ impl SpaceViewBlueprint {
     }
 
     pub fn clear(&self, ctx: &ViewerContext<'_>) {
-        // TODO: log a recursive clear
-        ctx.command_sender.send_system(SystemCommand::DropEntity(
-            ctx.store_context.blueprint.store_id().clone(),
-            self.entity_path(),
-        ));
+        // We can't delete the entity, because we need to support undo.
+        // TODO(#8249): configure blueprint GC to remove this entity if all that remains is the recursive clear.
+        let timepoint = ctx.store_context.blueprint_timepoint_for_writes();
+
+        let chunk = Chunk::builder(self.entity_path())
+            .with_archetype(
+                RowId::new(),
+                timepoint.clone(),
+                &re_types::archetypes::Clear::recursive(),
+            )
+            .build()
+            .unwrap();
+
+        ctx.command_sender
+            .send_system(SystemCommand::UpdateBlueprint(
+                ctx.store_context.blueprint.store_id().clone(),
+                vec![chunk],
+            ));
     }
 
     #[inline]

crates/viewer/re_viewport_blueprint/src/viewport_blueprint.rs

@@ -841,9 +841,8 @@ impl ViewportBlueprint {
             }
         }
 
-        // TODO: log a recursive clear here
-        // Clear any existing container blueprints that aren't referenced
-        // by any tiles.
+        // Clear any existing container blueprints that aren't referenced by any tiles,
+        // allowing the GC to remove the previous (non-clear) data from the store (saving RAM).
         for (container_id, container) in &self.containers {
             let tile_id = blueprint_id_to_tile_id(container_id);
             if self.tree.tiles.get(tile_id).is_none() {