better hardcoded string

Author: grtlr

crates/viewer/re_view_spatial/src/contexts/mod.rs

@@ -6,7 +6,7 @@ use re_tf::TransformInfo;
 use re_types::ViewClassIdentifier;
 use re_view::AnnotationSceneContext;
 
-pub use transform_tree_context::TransformTreeContext;
+pub use transform_tree_context::{TransformTreeContext, UNKNOWN_SPACE_ORIGIN};
 
 // -----------------------------------------------------------------------------
 

crates/viewer/re_view_spatial/src/contexts/transform_tree_context.rs

@@ -15,6 +15,12 @@ use vec1::smallvec_v1::SmallVec1;
 
 type FrameIdMapping = IntMap<TransformFrameIdHash, TransformFrameId>;
 
+/// Currently, there is no straightfoward way to retrieve the space origin
+/// when registering fallbacks. So, if unknown we set the target frame to a
+/// dummy string and rely on the view to supply that information after the
+/// first frame.
+pub const UNKNOWN_SPACE_ORIGIN: &str = "<unknown space origin>";
+
 /// Provides a transform tree for the view & time it operates on.
 ///
 /// Will do the necessary bulk processing of transform information and make it available
@@ -124,10 +130,10 @@ impl ViewContextSystem for TransformTreeContext {
             match target_frame_component {
                 Ok(target_frame) => {
                     let target_frame_str = target_frame.as_str();
-                    if !target_frame_str.is_empty() {
-                        TransformFrameIdHash::from_str(target_frame.as_str())
-                    } else {
+                    if target_frame_str == UNKNOWN_SPACE_ORIGIN {
                         self.transform_frame_id_for(query.space_origin.hash())
+                    } else {
+                        TransformFrameIdHash::from_str(target_frame.as_str())
                     }
                 }
                 Err(err) => {

crates/viewer/re_view_spatial/src/shared_fallbacks.rs

@@ -123,23 +123,4 @@ pub fn register_fallbacks(system_registry: &mut re_viewer_context::ViewSystemReg
             components::ShowLabels(false.into())
         },
     );
-
-    // Target reference frame - fallback to the computed value from view state
-    //
-    // An empty string signals that nothing has been set yet.
-    system_registry.register_fallback_provider(
-        blueprint::archetypes::SpatialInformation::descriptor_target_frame().component,
-        |ctx| {
-            let Ok(state) = ctx.view_state().downcast_ref::<SpatialViewState>() else {
-                return components::TransformFrameId(String::new().into());
-            };
-
-            // Return the computed target frame from the view state
-            state
-                .target_frame
-                .as_ref()
-                .map(|frame_str| components::TransformFrameId(frame_str.clone().into()))
-                .unwrap_or_else(|| components::TransformFrameId(String::new().into()))
-        },
-    );
 }

crates/viewer/re_view_spatial/src/view_3d.rs

@@ -11,7 +11,7 @@ use re_types::{
         archetypes::{Background, EyeControls3D, LineGrid3D, SpatialInformation},
         components::Eye3DKind,
     },
-    components::{LinearSpeed, Plane3D, Position3D, Vector3D},
+    components::{LinearSpeed, Plane3D, Position3D, TransformFrameId, Vector3D},
     datatypes::Vec3D,
     view_coordinates::SignedAxis3,
 };
@@ -27,7 +27,7 @@ use re_viewer_context::{
 use re_viewport_blueprint::ViewProperty;
 
 use crate::{
-    contexts::{TransformTreeContext, register_spatial_contexts},
+    contexts::{TransformTreeContext, UNKNOWN_SPACE_ORIGIN, register_spatial_contexts},
     heuristics::default_visualized_entities_for_visualizer_kind,
     spatial_topology::{HeuristicHints, SpatialTopology, SubSpaceConnectionFlags},
     ui::SpatialViewState,
@@ -251,6 +251,24 @@ impl ViewClass for SpatialView3D {
             },
         );
 
+        system_registry.register_fallback_provider(
+            SpatialInformation::descriptor_target_frame().component,
+            |ctx| {
+                let unknown_space_origin = || TransformFrameId(UNKNOWN_SPACE_ORIGIN.into());
+
+                let Ok(state) = ctx.view_state().downcast_ref::<SpatialViewState>() else {
+                    return unknown_space_origin();
+                };
+
+                // Return the computed target frame from the view state
+                state
+                    .target_frame
+                    .as_ref()
+                    .map(|frame_str| TransformFrameId(frame_str.clone().into()))
+                    .unwrap_or_else(unknown_space_origin)
+            },
+        );
+
         shared_fallbacks::register_fallbacks(system_registry);
 
         // Ensure spatial topology is registered.