Keep New Body and Offset Face previews moving during distance drags (#1238)

New Body extrusions and Offset Face previews show successful intermediate distances from the same setup while a distance drag runs, then compute the latest one (tool previews keep streaming as before; errors still need exact inputs). The drag arrow and value box are painted from this frame's pointer, removing a frame of lag. Drag regression tests and a perf note added.

ROADMAP.md

@@ -66,6 +66,13 @@ pointer movement orbits without a mouse button, and vertical scrolling zooms. Ot
 retain their saved two-finger scroll preference; camera motion is available through
 `view.navigate` and modifier-aware `ui.move` automation.
 
+## Interactive modelling
+
+- New Body extrusion and face-offset previews show completed intermediate geometry while a
+  drag continues, then catch up to the exact final value. Changes to the selected geometry,
+  operation or feature still discard obsolete results. Distance arrows and their value boxes
+  follow the current frame's input.
+
 ## Physical material data
 
 - Physical material card validation (#923/#922) provides typed SI mechanical and

crates/ui-egui/src/canvas.rs

@@ -527,17 +527,12 @@ fn drag_arrow(
 ) -> Option<Pos2> {
     let t = Tokens::get();
     let min = 40.0 * 2.0 * half_height / f64::from(proj.rect.height().max(1.0));
-    let shown = if l.abs() < min { min * if l < 0.0 { -1.0 } else { 1.0 } } else { l };
+    let tip = |length: f64| {
-    let ts = proj.to_screen(base + n * shown)?;
+        let shown = if length.abs() < min { min * if length < 0.0 { -1.0 } else { 1.0 } } else { length };
-    crate::scenario::publish_handle(if id == egui::Id::new("sc_manipulator") { "arrow" } else { "arrow2" }, ts);
+        proj.to_screen(base + n * shown)
+    };
+    let mut ts = tip(l)?;
     let r = ui.interact(egui::Rect::from_center_size(ts, vec2(20.0, 20.0)), id, egui::Sense::drag());
-    let hot = r.hovered() || r.dragged();
-    let col = if hot { t.accent } else { t.manipulator };
-    arrow(painter, bs, ts, col);
-    if hot {
-        painter.circle_stroke(ts, 8.0, Stroke::new(1.5, col));
-        ui.ctx().set_cursor_icon(egui::CursorIcon::Grab);
-    }
     if r.dragged()
         && let Some(p) = r.interact_pointer_pos()
         && let Some(v) = along(proj, p, base, n)
@@ -549,6 +544,17 @@ fn drag_arrow(
             v = v.max(if free { 1e-3 } else { step });
         }
         *value = format_len(v);
+        ts = tip(v)?;
+    }
+    // Paint the value just read from this frame's pointer, including the value box anchor.
+    // Using the old distance here made both trail the drag by another frame.
+    crate::scenario::publish_handle(if id == egui::Id::new("sc_manipulator") { "arrow" } else { "arrow2" }, ts);
+    let hot = r.hovered() || r.dragged();
+    let col = if hot { t.accent } else { t.manipulator };
+    arrow(painter, bs, ts, col);
+    if hot {
+        painter.circle_stroke(ts, 8.0, Stroke::new(1.5, col));
+        ui.ctx().set_cursor_icon(egui::CursorIcon::Grab);
     }
     Some(ts)
 }

crates/ui-egui/src/extrude_edit_tests.rs

@@ -361,3 +361,36 @@ fn symmetric_through_all_handle_drag_switches_to_total_distance() {
     let bounds = h.app.session.world_state().body("Main").unwrap().mesh().bounds();
     assert!((bounds.min.z + 60.0).abs() < 1e-7 && (bounds.max.z - 60.0).abs() < 1e-7);
 }
+
+/// Inspect each held frame, not just the settled end of the drag: the displayed arrow must
+/// be at the distance the pointer just wrote, rather than the previous frame's distance.
+#[test]
+fn extrusion_arrow_tracks_the_current_drag_frame() {
+    let mut h = make(json!({"distance":10}));
+    open(&mut h);
+    let at = h.at(&json!({"handle":"arrow"})).unwrap();
+    let at = egui::pos2(at[0] as f32, at[1] as f32);
+    h.app.synthetic_mods.ctrl = true;
+    h.app.synthetic.push(egui::Event::PointerMoved(at));
+    h.frame();
+    h.app.synthetic.push(egui::Event::PointerButton {
+        pos: at,
+        button: egui::PointerButton::Primary,
+        pressed: true,
+        modifiers: h.app.synthetic_mods,
+    });
+    h.frame();
+    for dy in [-20.0, -40.0, -60.0] {
+        h.app.synthetic.push(egui::Event::PointerMoved(at + egui::vec2(0.0, dy)));
+        h.frame();
+        let d = h.app.dialog.as_ref().unwrap();
+        let crate::dialogs::Kind::Extrude { distance, .. } = &d.kind else { panic!("extrude") };
+        let distance = h.app.session.doc.eval(distance, solidcraft_engine::doc::expr::Kind::Length).unwrap();
+        assert!(distance > 10.0);
+        let (base, normal) = crate::canvas::anchor(&h.app, d).unwrap();
+        let world = base + normal.unwrap() * distance;
+        let expected = h.at(&json!({"world":[world.x, world.y, world.z]})).unwrap();
+        let drawn = h.at(&json!({"handle":"arrow"})).unwrap();
+        assert!((drawn[0] - expected[0]).hypot(drawn[1] - expected[1]) < 0.1, "arrow {drawn:?} trails current value {expected:?}");
+    }
+}

crates/ui-egui/src/preview.rs

@@ -71,8 +71,8 @@ pub struct PreviewState {
     running: Option<(u64, Receiver<Job>)>,
     /// The running job builds a tool alone (for a join, cut or intersect).
     running_tool: bool,
-    /// Inputs of an in-flight joint preview, excluding only its driven values.
+    /// Inputs of a joint or distance preview, excluding only its driven values.
-    running_motion_key: Option<u64>,
+    running_stream_key: Option<u64>,
     /// Bodies the preview stands in for (hidden in the model scene).
     pub replaced: Vec<String>,
     /// The preview scene for the GPU and its key (changes whenever the scene does).
@@ -102,7 +102,7 @@ impl PreviewState {
     fn clear(&mut self) {
         self.running = None;
         self.running_tool = false;
-        self.running_motion_key = None;
+        self.running_stream_key = None;
         self.shown_key = None;
         self.error = None;
         self.applied = None;
@@ -152,7 +152,7 @@ impl PreviewState {
 
     /// Errors validate only the current inputs. Keep the last good geometry while
     /// computing new inputs, but never let an obsolete result block their Apply.
-    fn poll(&mut self, key: u64, motion_key: Option<u64>) {
+    fn poll(&mut self, key: u64, stream_key: Option<u64>) {
         if self.shown_key != Some(key) {
             self.sketches.clear();
             self.error = None;
@@ -167,11 +167,11 @@ impl PreviewState {
             if let Some(job) = job {
                 self.running = None;
                 let good = matches!(&job, Ok(b) if b.error.is_none());
-                let intermediate = good && (self.running_tool || motion_key.is_some() && self.running_motion_key == motion_key);
+                let intermediate = good && (self.running_tool || stream_key.is_some() && self.running_stream_key == stream_key);
-                self.running_motion_key = None;
+                self.running_stream_key = None;
                 self.running_tool = false;
                 // A held slider, a dragged arrow or an animation may advance faster than the
-                // worker. Show completed poses from the same joint setup, and tools built for
+                // worker. Show completed joint/distance results from the same setup, and tools built for
                 // inputs since changed, then compute the latest. Errors still require an exact
                 // key.
                 if k == key || intermediate {
@@ -209,6 +209,41 @@ fn motion_key(cmds: &[(String, Value)], revision: u64, colors: Colors) -> Option
     Some(h.finish())
 }
 
+/// Tool previews already stream in `poll`. New-body extrusions and face offsets instead
+/// build their full result; allow successful intermediate distances only within the same
+/// setup. Preserve selections, feature identity, extent mode, revision and colours. The
+/// exact job key still ensures the latest distance is computed and errors never go stale.
+fn stream_key(cmds: &[(String, Value)], revision: u64, colors: Colors) -> Option<u64> {
+    if let Some(key) = motion_key(cmds, revision, colors) {
+        return Some(key);
+    }
+    if cmds.is_empty() || as_new_body(cmds).is_some() {
+        return None;
+    }
+    let mut setup = cmds.to_vec();
+    for (command, params) in &mut setup {
+        let (command, params) = if command == "timeline.redefine" {
+            let command = params.get("command")?.as_str()?.to_string();
+            (command, params.get_mut("params")?)
+        } else {
+            (command.clone(), params)
+        };
+        let fields: &[&str] = match command.as_str() {
+            "solid.extrude" => &["distance", "distance2", "to_offset"],
+            "solid.offset_face" => &["distance"],
+            _ => return None,
+        };
+        let params = params.as_object_mut()?;
+        for field in fields {
+            // Keep presence: changing extent mode must not reuse the old result.
+            if let Some(value) = params.get_mut(*field) {
+                *value = Value::Null;
+            }
+        }
+    }
+    Some(job_key(&setup, revision, colors))
+}
+
 /// Keep the preview in step with the open dialog: start a computation when its inputs changed,
 /// take finished results. Called once per frame.
 pub fn update(app: &mut SolveApp, ctx: &egui::Context) {
@@ -227,13 +262,13 @@ pub fn update(app: &mut SolveApp, ctx: &egui::Context) {
     };
     let colors = Colors::from_tokens(&Tokens::get());
     let key = job_key(&cmds, app.session.revision, colors);
-    let motion_key = motion_key(&cmds, app.session.revision, colors);
+    let stream_key = stream_key(&cmds, app.session.revision, colors);
     let tool = as_new_body(&cmds).is_some();
     let pv = &mut app.preview;
-    pv.poll(key, motion_key);
+    pv.poll(key, stream_key);
     if pv.running.is_none() && pv.shown_key != Some(key) {
         pv.started = crate::now_ms();
-        pv.running_motion_key = motion_key;
+        pv.running_stream_key = stream_key;
         let scratch = app.session.scratch();
         spawn(&mut app.preview, key, scratch, cmds, colors, tool);
     }
@@ -720,7 +755,7 @@ mod tests {
         for (running, wanted) in [(1, 2), (2, 3), (3, 4)] {
             let (tx, rx) = std::sync::mpsc::channel();
             pv.running = Some((running, rx));
-            pv.running_motion_key = Some(42);
+            pv.running_stream_key = Some(42);
             pv.poll(wanted, Some(42));
             assert!(pv.running.is_some());
             tx.send(Ok(pose())).unwrap();
@@ -733,7 +768,7 @@ mod tests {
         }
         let (tx, rx) = std::sync::mpsc::channel();
         pv.running = Some((4, rx));
-        pv.running_motion_key = Some(42);
+        pv.running_stream_key = Some(42);
         tx.send(Ok(pose())).unwrap();
         pv.poll(4, Some(42));
         assert_eq!(pv.shown_key, Some(4), "release catches up to the exact final pose");
@@ -748,7 +783,7 @@ mod tests {
             (Some(42), Err("old invalid value".into())),
             (Some(42), Ok(Built { error: Some("old tool preview error".into()), ..pose() })),
         ] {
-            let mut pv = PreviewState { running_motion_key: Some(42), ..PreviewState::default() };
+            let mut pv = PreviewState { running_stream_key: Some(42), ..PreviewState::default() };
             let (tx, rx) = std::sync::mpsc::channel();
             pv.running = Some((1, rx));
             tx.send(job).unwrap();
@@ -997,3 +1032,7 @@ mod tests {
         assert!(pv.error.is_none() && pv.shown_key == Some(1), "an old error is dropped");
     }
 }
+
+#[cfg(test)]
+#[path = "preview_drag_tests.rs"]
+mod drag_tests;

crates/ui-egui/src/preview_drag_tests.rs

@@ -0,0 +1,149 @@
+//! Completed distances must reach the viewport before a continuously moving pointer stops.
+use super::*;
+use serde_json::json;
+
+fn colors() -> Colors {
+    Colors { body: [1, 1, 1, 255], added: [2, 2, 2, 255], removed: [3, 3, 3, 100], edge: [0, 0, 0, 255] }
+}
+
+fn fixture() -> Session {
+    let mut s = Session::new(solidcraft_engine::doc::Document::new("Preview drag"));
+    s.execute("sketch.create", &json!({"plane":"XY", "name":"Profile"})).unwrap();
+    s.execute("sketch.rectangle.two_point", &json!({"p0":[0,0], "p1":[10,10]})).unwrap();
+    s.execute("sketch.finish", &json!({})).unwrap();
+    s
+}
+
+fn extrude(distance: i32) -> Vec<(String, Value)> {
+    vec![("solid.extrude".into(), json!({"sketch":"Profile", "distance":distance, "operation":"new"}))]
+}
+
+fn check_drag(s: &Session, commands: impl Fn(i32) -> Vec<(String, Value)>, base_z: f64) {
+    let original = serde_json::to_value(&*s.doc).unwrap();
+    let undo = s.undo.len();
+    let mut pv = PreviewState::default();
+    for (finished, wanted) in [(10, 20), (20, 30), (30, 30)] {
+        let old = commands(finished);
+        let new = commands(wanted);
+        let old_key = job_key(&old, s.revision, colors());
+        let key = job_key(&new, s.revision, colors());
+        let (tx, rx) = std::sync::mpsc::channel();
+        pv.running = Some((old_key, rx));
+        pv.running_tool = as_new_body(&old).is_some();
+        pv.running_stream_key = stream_key(&old, s.revision, colors());
+        let built = compute_tool(s, &old, colors()).unwrap();
+        tx.send(Ok(built)).unwrap();
+        pv.poll(key, stream_key(&new, s.revision, colors()));
+        assert!(pv.active && pv.error.is_none(), "completed geometry must show during the drag: {:?}", pv.error);
+        assert!((pv.bounds.max.z - base_z - f64::from(finished)).abs() < 1e-8);
+        assert_eq!(pv.shown_key, Some(old_key));
+        assert_eq!(pv.shown_key == Some(key), finished == wanted, "only the final distance satisfies the latest request");
+        assert!(pv.running.is_none());
+    }
+    assert_eq!(serde_json::to_value(&*s.doc).unwrap(), original);
+    assert_eq!(s.undo.len(), undo);
+}
+
+#[test]
+fn new_body_extrude_keeps_moving_during_a_drag() {
+    check_drag(&fixture(), extrude, 0.0);
+}
+
+#[test]
+fn edited_new_body_extrude_keeps_moving_during_a_drag() {
+    let mut s = fixture();
+    let feature = s.execute("solid.extrude", &extrude(5)[0].1).unwrap()["feature"].as_u64().unwrap();
+    check_drag(
+        &s,
+        |distance| vec![("timeline.redefine".into(), json!({"feature":feature,"command":"solid.extrude","params":extrude(distance)[0].1}))],
+        0.0,
+    );
+}
+
+#[test]
+fn face_offset_keeps_moving_during_a_drag() {
+    let mut s = Session::new(solidcraft_engine::doc::Document::new("Face offset drag"));
+    s.execute("solid.box", &json!({"length":10,"width":10,"height":10})).unwrap();
+    check_drag(&s, |distance| vec![("solid.offset_face".into(), json!({"faces":[[5,5,10]],"distance":distance}))], 10.0);
+}
+
+#[test]
+fn join_tool_keeps_moving_without_waiting_for_its_boolean() {
+    let mut s = fixture();
+    s.execute("solid.box", &json!({"length":10,"width":10,"height":5})).unwrap();
+    check_drag(&s, |distance| vec![("solid.extrude".into(), json!({"sketch":"Profile","distance":distance,"operation":"join"}))], 0.0);
+}
+
+#[test]
+fn distance_stream_keeps_feature_selection_and_extent_context() {
+    let old = extrude(10);
+    let key = stream_key(&old, 7, colors());
+    assert!(key.is_some());
+    assert_eq!(key, stream_key(&extrude(20), 7, colors()));
+    assert_ne!(key, stream_key(&old, 8, colors()));
+    let mut recolored = colors();
+    recolored.added = [40, 50, 60, 255];
+    assert_ne!(key, stream_key(&old, 7, recolored));
+    for (field, value) in [
+        ("sketch", json!("Other")),
+        ("profiles", json!([1])),
+        ("face", json!([0, 0, 5])),
+        ("operation", json!("cut")),
+        ("direction", json!("negative")),
+        ("distance2", json!(5)),
+        ("to", json!([0, 0, 50])),
+        ("taper", json!(5)),
+        ("start_offset", json!(3)),
+        ("participants", json!(["Other"])),
+    ] {
+        let mut changed = old.clone();
+        changed[0].1[field] = value;
+        assert_ne!(key, stream_key(&changed, 7, colors()), "changed {field} cannot reuse the old result");
+    }
+    for field in ["distance2", "to_offset"] {
+        let mut from = old.clone();
+        from[0].1[field] = json!(5);
+        let mut to = from.clone();
+        to[0].1[field] = json!(9);
+        assert_eq!(stream_key(&from, 7, colors()), stream_key(&to, 7, colors()));
+    }
+    let edit =
+        |feature, distance| vec![("timeline.redefine".into(), json!({"feature":feature,"command":"solid.extrude","params":extrude(distance)[0].1}))];
+    assert_eq!(stream_key(&edit(2, 10), 7, colors()), stream_key(&edit(2, 20), 7, colors()));
+    assert_ne!(stream_key(&edit(2, 10), 7, colors()), stream_key(&edit(3, 20), 7, colors()));
+    assert_ne!(key, stream_key(&edit(2, 10), 7, colors()));
+    let offset = |distance| vec![("solid.offset_face".into(), json!({"faces":[[5,5,10]],"distance":distance}))];
+    assert!(stream_key(&offset(1), 7, colors()).is_some());
+    assert_eq!(stream_key(&offset(1), 7, colors()), stream_key(&offset(5), 7, colors()));
+    assert!(stream_key(&[], 7, colors()).is_none());
+    assert!(stream_key(&[("solid.fillet".into(), json!({"radius":5}))], 7, colors()).is_none());
+    let mut mixed = old;
+    mixed.push(("select.clear".into(), json!({})));
+    assert!(stream_key(&mixed, 7, colors()).is_none());
+}
+
+#[test]
+fn distance_results_reject_other_setups_and_obsolete_errors() {
+    let s = fixture();
+    let old = extrude(10);
+    let current = extrude(20);
+    for (revision, failed) in [(s.revision + 1, false), (s.revision, true)] {
+        let mut built = compute_tool(&s, &old, colors()).unwrap();
+        if failed {
+            built.error = Some("old distance failed".into());
+        }
+        let (tx, rx) = std::sync::mpsc::channel();
+        let mut pv = PreviewState {
+            running: Some((job_key(&old, s.revision, colors()), rx)),
+            running_stream_key: stream_key(&old, s.revision, colors()),
+            ..Default::default()
+        };
+        tx.send(Ok(built)).unwrap();
+        pv.poll(job_key(&current, revision, colors()), stream_key(&current, revision, colors()));
+        assert!(!pv.active && pv.error.is_none() && pv.shown_key.is_none());
+    }
+    let mut join = current.clone();
+    join[0].1["operation"] = json!("join");
+    assert!(as_new_body(&join).is_some());
+    assert!(stream_key(&join, s.revision, colors()).is_none(), "tool previews retain their upstream streaming path");
+}

docs/perf.md

@@ -816,3 +816,40 @@ observed 47.6 ms check; no local PNG was created and the active document remaine
 empty. The screenshot shows the transferred file's picture while built-in sample
 pictures are still loading. This is one functional visual check, not a first-frame
 benchmark. The separate counting-reader regression proves source-blob deferral.
+
+## Extrude drag preview delivery
+
+On macOS with Metal, editing a 15 mm radius cylinder's 10 mm extrusion and dragging its
+arrow upward by 150 screen points (120 input steps, Ctrl held) exposed preview starvation.
+A completed worker result was discarded whenever the pointer had already changed the
+requested distance. The arrow also drew the previous frame's distance.
+
+Main's tool-only preview already delivers intermediate Join/Cut/Intersect geometry. New Body
+extrusions (including feature edits) and Offset Face use full-result previews and still discard
+completed distances during a moving drag. Those paths now accept successful intermediate
+distances from the same setup. Selections, operation, extent mode, feature identity, revision
+and colours remain part of the setup identity. Errors still apply only to the exact requested
+inputs, and the final distance is computed normally. Tool previews and background Apply retain
+their existing paths. The arrow and value-box anchor use the current frame's pointer value.
+
+Release-build control-channel checks against upstream `4dc63810` with the arrow fix alone,
+then with the distance fallback, used the same 150-point, 120-step drags. The cylinder used
+the setup above; planar-face Press Pull (Join) and Offset Face used a 30 × 30 × 10 mm box.
+The samples captured 25–27 distinct requested distances per drag:
+
+| Preview updates before reaching the final distance | Main + arrow fix | With distance fallback |
+|---|---:|---:|
+| Edited New Body extrusion | 0 | 24 |
+| Planar-face Press Pull (Join) | 22 | 24 |
+| Offset Face | 0 | 23 |
+
+Join already streams on main; the small count difference reflects sampling, not a change to
+that path. Applying the fixed New Body extrusion produced the requested 19.585 mm height;
+applying the 11.672 mm face offset produced a 21.672 mm tall box.
+
+These are sampled preview deliveries (`ui.inspect.preview.ms` changes), not every rendered
+frame or a geometry-kernel speed benchmark. With main's preview code unchanged, the New Body,
+edited New Body and Offset Face drag regressions fail while Join passes. With the fallback,
+all six distance-preview regressions pass, covering intermediate geometry, exact final
+convergence, unchanged document/undo, obsolete errors and setup changes. A separate regression
+checks the arrow's position on each held input frame.