fix(snap): improve OTRACK and extension snapping

src/app/update/viewport.rs

@@ -253,17 +253,44 @@ impl OpenCADStudio {
         eye: glam::DVec3,
         bounds: iced::Rectangle,
     ) -> Option<crate::snap::OtrackHit> {
-        if snap.is_some_and(|hit| hit.snap_type != crate::snap::SnapType::Extension) {
+        let intersection = snap.filter(|hit| {
+            hit.snap_type == crate::snap::SnapType::Intersection
+        });
+
+        // Ordinary object snaps suppress OTRACK. Extension and Intersection are
+        // exceptions: both may lie on an active tracking vector.
+        if snap.is_some_and(|hit| {
+            !matches!(
+                hit.snap_type,
+                crate::snap::SnapType::Extension | crate::snap::SnapType::Intersection
+            )
+        }) {
             return None;
         }
+
         let required_crossing_ray = match snap {
-            Some(extension) => Some((extension.extension_origin?, extension.extension_dir?)),
+            Some(extension)
-            None => None,
+                if extension.snap_type == crate::snap::SnapType::Extension =>
+            {
+                Some((
+                    extension.extension_origin?,
+                    extension.extension_dir?,
+                ))
+            }
+            _ => None,
         };
+
+        // When Intersection has already won OSNAP selection, test OTRACK at the
+        // exact intersection rather than at the free cursor position.
+        let track_cursor = intersection
+            .map(|hit| hit.world)
+            .unwrap_or(cursor);
+
         let step = (self.polar_mode && drafting).then_some(self.polar_increment_deg);
         let (_, (ucs_x, ucs_y, _)) = self.drafting_grid_basis(tab);
-        let hit = self.snapper.otrack_snap(
+
-            cursor,
+        let mut hit = self.snapper.otrack_snap(
+            track_cursor,
             view_rot,
             eye,
             bounds,
@@ -274,6 +301,28 @@ impl OpenCADStudio {
             ucs_x.as_dvec3(),
             ucs_y.as_dvec3(),
         )?;
+
+        if let Some(intersection) = intersection {
+            // Only keep the vector when it really passes through the highlighted
+            // intersection. This avoids showing an unrelated nearby tracking ray.
+            let ndc = view_rot.project_point3((hit.aligned - eye).as_vec3());
+            let aligned_screen = iced::Point::new(
+                (ndc.x + 1.0) * 0.5 * bounds.width,
+                (1.0 - ndc.y) * 0.5 * bounds.height,
+            );
+
+            let dx = aligned_screen.x - intersection.screen.x;
+            let dy = aligned_screen.y - intersection.screen.y;
+
+            if dx * dx + dy * dy > 4.0 {
+                return None;
+            }
+
+            // OTRACK is only providing the visual/reference vector here.
+            // Intersection remains the exact picked point.
+            hit.aligned = intersection.world;
+        }
+
         Some(hit)
     }
 
@@ -1217,7 +1266,14 @@ impl OpenCADStudio {
                 // Keep the entity's original geometry available for self-OSNAP,
                 // Extension and OTRACK while the live grip preview is being deformed.
                 self.grip_snap_wires = snap.clone();
-
+                // The user explicitly picked this grip, so treat its original position as an
+                // acquired tracking point immediately. This lets Extension/OTRACK use the
+                // original edge direction on the very first movement instead of requiring the
+                // cursor to return to the old grip position and dwell there first.
+                self.snapper.acquire_grip_tracking_point(
+                    grip.origin_world,
+                    &self.grip_snap_wires,
+                );
                 self.grip_text_verts = snap
                     .iter()
                     .flat_map(|w| w.text_verts.iter().copied())
@@ -1756,6 +1812,49 @@ impl OpenCADStudio {
                 self.axis_lock_dir = None;
                 None
             };
+            // An acquired OTRACK ray can cross real drawing geometry even before the
+            // command has a first point. Probe the active tracking ray and let the normal
+            // snap engine evaluate that ray against nearby geometry as a construction ray.
+            //
+            // This makes OTRACK × entity crossings real Intersection snaps, so the normal
+            // dwell acquisition can subsequently turn the crossing into a tracking point.
+            if axis_lock.is_none() && !is_window_corner {
+                let tracking_probe = self.active_otrack_hit(
+                    i,
+                    cursor_world,
+                    None,
+                    self.last_point,
+                    true,
+                    view_rot,
+                    eye,
+                    bounds,
+                );
+
+                if let Some(track) = tracking_probe {
+                    let (go, gr) = self.drafting_grid_basis(i);
+
+                    let tracked_snap = self.snapper.snap(
+                        snap_cursor,
+                        p,
+                        &snap_candidates,
+                        view_rot,
+                        eye,
+                        bounds,
+                        go,
+                        gr,
+                        Some((track.base, track.base + track.dir)),
+                    );
+
+                    // The second pass exists only to discover a crossing between the
+                    // active OTRACK ray and real geometry. Keep the original snap result
+                    // for every other kind of snap.
+                    if tracked_snap
+                        .is_some_and(|hit| hit.snap_type == crate::snap::SnapType::Intersection)
+                    {
+                        self.tabs[i].snap_result = tracked_snap;
+                    }
+                }
+            }
             self.snapper.update_otrack_dwell(
                 self.tabs[i].snap_result,
                 &snap_candidates,
@@ -3055,7 +3154,7 @@ impl OpenCADStudio {
                     .as_ref()
                     .map(|c| c.needs_entity_pick())
                     .unwrap_or(false);
-                let snap_hit = if needs_entity_click {
+                let mut snap_hit = if needs_entity_click {
                     None
                 } else if needs_tan {
                     self.snapper.snap_tangent_only(
@@ -3097,6 +3196,43 @@ impl OpenCADStudio {
                         construction_ray,
                     )
                 };
+                // Mirror the cursor-move OTRACK × geometry intersection pass when the
+                // point is actually clicked. The move path may already display the
+                // Intersection marker, but click handling recomputes snapping from scratch.
+                if !needs_entity_click && !needs_tan && !is_window_corner {
+                    let tracking_probe = self.active_otrack_hit(
+                        i,
+                        raw,
+                        None,
+                        self.last_point,
+                        true,
+                        view_rot,
+                        eye,
+                        bounds,
+                    );
+
+                    if let Some(track) = tracking_probe {
+                        let (go, gr) = self.drafting_grid_basis(i);
+
+                        let tracked_snap = self.snapper.snap(
+                            snap_cursor,
+                            p,
+                            &snap_candidates,
+                            view_rot,
+                            eye,
+                            bounds,
+                            go,
+                            gr,
+                            Some((track.base, track.base + track.dir)),
+                        );
+
+                        if tracked_snap
+                            .is_some_and(|hit| hit.snap_type == crate::snap::SnapType::Intersection)
+                        {
+                            snap_hit = tracked_snap;
+                        }
+                    }
+                }
                 // Snap runs in model space; the result is already model.
                 let mut pt = snap_hit.map(|s| s.world).unwrap_or(raw);
                 // When no UCS is active clamp to world XY; with a UCS the point is

src/snap.rs

@@ -382,7 +382,24 @@ impl Snapper {
             }
         }
     }
+    /// Immediately acquire an explicit grip origin as a tracking point.
+    ///
+    /// Unlike normal cursor acquisition, a grip was deliberately selected by the
+    /// user, so it should not require OTRACK dwell before Extension/OTRACK can use it.
+    pub fn acquire_grip_tracking_point<W: WireSource + ?Sized>(
+        &mut self,
+        p: DVec3,
+        wires: &W,
+    ) {
+        if !self.tracking_active() {
+            return;
+        }
 
+        // With OTRACK disabled, Extension acquisition must remain endpoint-only.
+        let endpoints_only = !self.otrack_enabled;
+
+        self.acquire_tracking_point(p, wires, endpoints_only);
+    }
     /// Add `p` as a tracking point (capturing its corner edge directions) unless
     /// it is already tracked; drops the oldest when the 4-point cap is reached.
     /// Edge directions are scanned once here, at acquisition, so OTRACK can align
@@ -1255,7 +1272,31 @@ impl Snapper {
                 }
             }
         };
-
+        // Check engaged extension tracking rays against nearby real geometry.
+        // OTRACK can align the cursor to an acquired segment extension even when
+        // Extension OSNAP itself is not the current snap result. Allow Intersection
+        // to stop that active extension ray where it crosses drawing geometry.
+        if self.is_on(SnapType::Intersection) && self.otrack_enabled {
+            for (&origin, dirs) in self.tracking_points.iter().zip(&self.tracking_dirs) {
+                for &dir in dirs {
+                    // Only test the extension ray while the cursor is actually
+                    // engaged with it, so Intersection does not become Nearest.
+                    if extension_snap(
+                        cursor_world,
+                        origin,
+                        dir,
+                        view_rot,
+                        eye,
+                        bounds,
+                        self.osnap_radius_px,
+                    )
+                    .is_some()
+                    {
+                        try_ray_intersections(origin, origin + dir);
+                    }
+                }
+            }
+        }
         if self.is_on(SnapType::Intersection) {
             if let Some((origin, through)) = construction_ray {
                 try_ray_intersections(origin, through);