Support tracking and direct distance input for grip editing

src/app/update/dynamic.rs

@@ -22,6 +22,25 @@ use iced::{mouse, Point, Task};
 
 
 impl OpenCADStudio {
+    pub(in crate::app) fn active_distance_ray(
+        &self,
+        i: usize,
+    ) -> Option<(glam::DVec3, glam::DVec3)> {
+        // OTRACK already exposes its acquired world-space ray.
+        if let Some((base, dir)) = self.otrack_active {
+            return Some((base, dir));
+        }
+
+        // Extension stores the snapped point. Recover the acquired endpoint
+        // and outward segment direction that produced that snap.
+        let snap = self.tabs[i].snap_result?;
+
+        if snap.snap_type == crate::snap::SnapType::Extension {
+            return self.snapper.extension_input_ray(snap.world);
+        }
+
+        None
+    }
     /// Rebuild the active tab's dynamic-input field set to match what the
     /// command is currently asking for. Called on cursor move and after
     /// command-state changes. The field set only changes shape when the
@@ -79,11 +98,11 @@ impl OpenCADStudio {
         let has_base = self.last_point.is_some();
         // While aligned to an OTRACK ray, the point step reads a single
         // distance along the ray (issue #69) — show one Distance box.
-        let otrack_dist = self.otrack_active.is_some()
+        let guided_dist = self.active_distance_ray(i).is_some()
             && !wants_text
             && matches!(field, crate::command::DynField::Point);
         let default: Vec<DynComponent> = match field {
-            _ if otrack_dist => vec![DynComponent::Distance],
+            _ if guided_dist => vec![DynComponent::Distance],
             crate::command::DynField::Distance => vec![DynComponent::Distance],
             crate::command::DynField::Angle => vec![DynComponent::Angle],
             crate::command::DynField::Scalar => vec![DynComponent::Scalar],
@@ -528,9 +547,9 @@ impl OpenCADStudio {
         {
             return None;
         }
-        // OTRACK: while aligned to a tracking ray, a typed value is a distance
-        // along the ray from the tracking point (issue #69).
-        if let Some((base, dir)) = self.otrack_active {
+        // OTRACK and Extension both allow a typed scalar to act as a
+        // distance measured along the active reference ray.
+        if let Some((base, dir)) = self.active_distance_ray(i) {
             let wants_text = self.tabs[i]
                 .active_cmd
                 .as_ref()