LR-EDIT-CURVE: drag point-curve points in both axes

The editor stored the dragged point index as Option<usize> but read it back
as usize, so the index was lost after the first frame: pressing on a point
did nothing and only click-to-add (overwrite) worked. Points now drag in X
and Y (X clamped between the neighbours), picked at the press origin, with a
grab cursor, a highlighted point and an input/output readout; one undo step
per drag via develop.beginInteraction / endInteraction.

Fixes #12

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/ui-egui/src/lib.rs

@@ -22,6 +22,8 @@ pub mod state;
 pub mod theme;
 pub mod widgets;
 
+#[cfg(test)]
+mod tests_curve;
 #[cfg(test)]
 mod tests_masking;
 #[cfg(test)]

crates/ui-egui/src/panels/edit.rs

@@ -677,13 +677,37 @@ fn curve_editor(app: &mut LightcraftApp, ui: &mut egui::Ui, id: PhotoId, d: &Dev
     };
     let line: Vec<Pos2> = (0..=96).map(|i| to_screen(i as f64 / 96.0, curve.eval(i as f64 / 96.0).clamp(0.0, 1.0))).collect();
     p.add(egui::Shape::line(line, Stroke::new(2.0, color)));
-    for q in &pts {
-        p.circle_filled(to_screen(q.x, q.y), 4.0, color);
-    }
-    // interaction: drag the nearest point, click empty space to add, double-click to delete
+    // interaction: drag a point (both axes, between its neighbours), drag empty space to add and
+    // drag a new point, click empty space to add, double-click a point to delete it
     let drag_id = egui::Id::new(("curve-drag", &ch));
-    let mut dragging: Option<usize> = ui.data(|dd| dd.get_temp(drag_id));
+    // the point being dragged (stored as `Option<usize>` so a stale value can be cleared)
+    let mut dragging: Option<usize> = ui.data(|dd| dd.get_temp::<Option<usize>>(drag_id)).flatten();
     let nearest = |q: Pos2| pts.iter().enumerate().map(|(i, p)| (i, to_screen(p.x, p.y).distance(q))).min_by(|a, b| a.1.total_cmp(&b.1));
+    let hovered = resp.hover_pos().and_then(nearest).filter(|(_, dist)| *dist < 10.0).map(|(i, _)| i);
+    if dragging.is_some() {
+        ui.ctx().set_cursor_icon(egui::CursorIcon::Grabbing);
+    } else if hovered.is_some() {
+        ui.ctx().set_cursor_icon(egui::CursorIcon::Grab);
+    }
+    for (i, q) in pts.iter().enumerate() {
+        let c = to_screen(q.x, q.y);
+        if dragging == Some(i) || (dragging.is_none() && hovered == Some(i)) {
+            p.circle_filled(c, 5.5, color);
+            p.circle_stroke(c, 5.5, Stroke::new(1.0, t.canvas));
+        } else {
+            p.circle_filled(c, 4.0, color);
+        }
+    }
+    // input / output readout of the point being dragged (0–255 like the histogram)
+    if let Some(q) = dragging.and_then(|i| pts.get(i)) {
+        p.text(
+            r.left_top() + vec2(6.0, 4.0),
+            egui::Align2::LEFT_TOP,
+            format!("{} / {}", (q.x * 255.0).round(), (q.y * 255.0).round()),
+            t.font(11.0),
+            t.text_dim,
+        );
+    }
     let mut new_pts = None;
     if resp.double_clicked()
         && let Some(q) = resp.interact_pointer_pos()
@@ -696,8 +720,9 @@ fn curve_editor(app: &mut LightcraftApp, ui: &mut egui::Ui, id: PhotoId, d: &Dev
         v.remove(i);
         new_pts = Some(v);
     } else if resp.drag_started()
-        && let Some(q) = resp.interact_pointer_pos()
+        && let Some(q) = ui.input(|i| i.pointer.press_origin()).or(resp.interact_pointer_pos())
     {
+        // pick the point under the press, not where the pointer is once the drag threshold passed
         let _ = app.run("develop.beginInteraction", json!({"label": "Tone Curve"}));
         match nearest(q) {
             Some((i, dist)) if dist < 10.0 => dragging = Some(i),

crates/ui-egui/src/tests_curve.rs

@@ -0,0 +1,86 @@
+//! Headless tests of the point-curve editor: dragging points, resetting, presets.
+
+use std::time::Duration;
+
+use serde_json::json;
+
+use crate::headless::Headless;
+use crate::{LightcraftApp, Services};
+
+const T: Duration = Duration::from_secs(20);
+
+/// Detail view with the Edit panel's Curve flyout open on `channel`.
+fn curve_open(channel: &str) -> Headless {
+    let services = Services { png: None, ..Default::default() };
+    let app = LightcraftApp::new(lightcraft_engine::Session::with_demo(), services);
+    let mut h = Headless::new(app, [1200.0, 1400.0], 1.0);
+    let r = h.request("ui.set", json!({"view": "detail"}), T);
+    assert_eq!(r["ok"], true, "{r}");
+    h.app.ui.right = crate::state::RightPanel::Edit;
+    if !h.app.ui.section_open("light") {
+        h.app.ui.toggle_section("light");
+    }
+    if !h.app.ui.flyout_open("curve") {
+        h.app.ui.toggle_flyout("curve");
+    }
+    h.app.ui.curve_channel = channel.into();
+    h.step();
+    h.step();
+    h
+}
+
+fn exec(h: &mut Headless, command: &str, params: serde_json::Value) -> serde_json::Value {
+    let r = h.request("engine.execute", json!({"command": command, "params": params}), T);
+    assert_eq!(r["ok"], true, "{command}: {r}");
+    r["result"].clone()
+}
+
+fn develop(h: &Headless) -> lightcraft_develop::DevelopSettings {
+    let id = h.app.session.active().expect("active photo");
+    (*h.app.session.develop_of(id).unwrap_or_default()).clone()
+}
+
+fn pts(v: &[lightcraft_geom::Point]) -> Vec<(f64, f64)> {
+    v.iter().map(|p| (p.x, p.y)).collect()
+}
+
+/// Side of the (square) curve graph in screen points.
+fn curve_side(h: &mut Headless) -> f64 {
+    let r = h.request("ui.widgets", json!({"filter": "curve"}), T);
+    let w = r["result"].as_array().unwrap().iter().find(|w| w["id"] == "curve").cloned().unwrap_or_else(|| panic!("curve widget on screen: {r}"));
+    w["rect"][2].as_f64().unwrap()
+}
+
+#[test]
+fn dragging_a_point_moves_it_in_both_axes_with_one_undo_step() {
+    let mut h = curve_open("master");
+    exec(&mut h, "develop.curve", json!({"channel": "master", "points": [[0.0, 0.0], [0.5, 0.5], [1.0, 1.0]]}));
+    h.step();
+    let side = curve_side(&mut h);
+    let undo_before = h.app.session.undo.len();
+    // grab the middle point and drag it up-left: x 0.5 → 0.4, y 0.5 → 0.7
+    let r = h.request("ui.dragWidget", json!({"id": "curve", "fx": 0.5, "fy": 0.5, "dx": -0.1 * side, "dy": -0.2 * side, "steps": 12}), T);
+    assert_eq!(r["ok"], true, "{r}");
+    h.step();
+    let c = pts(&develop(&h).curve.master);
+    assert_eq!(c.len(), 3, "dragging moves the point, it doesn't add one: {c:?}");
+    assert!((c[1].0 - 0.4).abs() < 0.03, "x follows the pointer: {c:?}");
+    assert!((c[1].1 - 0.7).abs() < 0.03, "y follows the pointer: {c:?}");
+    assert_eq!(h.app.session.undo.len(), undo_before + 1, "one undo step per drag");
+}
+
+#[test]
+fn dragging_a_point_past_its_neighbour_is_clamped() {
+    let mut h = curve_open("red");
+    exec(&mut h, "develop.curve", json!({"channel": "red", "points": [[0.0, 0.0], [0.3, 0.3], [0.6, 0.6], [1.0, 1.0]]}));
+    h.step();
+    let side = curve_side(&mut h);
+    // drag the point at 0.3 far to the right (past 0.6)
+    let r = h.request("ui.dragWidget", json!({"id": "curve", "fx": 0.3, "fy": 0.7, "dx": 0.5 * side, "dy": 0.0, "steps": 12}), T);
+    assert_eq!(r["ok"], true, "{r}");
+    h.step();
+    let c = pts(&develop(&h).curve.red);
+    assert_eq!(c.len(), 4, "{c:?}");
+    assert!(c[1].0 < c[2].0 && c[1].0 > 0.55, "clamped just left of its neighbour: {c:?}");
+    assert_eq!(c[2], (0.6, 0.6), "the neighbour stays: {c:?}");
+}

docs/parity.md

@@ -211,7 +211,7 @@ under the UI command that wraps it (a no-op error); the UI command now wins.
 | LR-EDIT-LIGHT-WHITES | Whites | P0 | ✅ | `ctl:light.whites` | |
 | LR-EDIT-LIGHT-BLACKS | Blacks | P0 | ✅ | `ctl:light.blacks` | |
 | LR-EDIT-LIGHT-CURVE-PARAM | Parametric curve | P0 | ✅ | `ctl:curve.highlights`, `ctl:curve.lights`, `ctl:curve.darks`, `ctl:curve.shadows`, `ctl:curve.split*` | |
-| LR-EDIT-LIGHT-CURVE-POINT | Point curve | P0 | ✅ | `cmd:develop.curve`, `crates/ui-egui/src/panels/edit.rs` | no curve presets (linear / medium / strong) |
+| LR-EDIT-LIGHT-CURVE-POINT | Point curve | P0 | ✅ | `cmd:develop.curve`, `crates/ui-egui/src/panels/edit.rs` | click to add a point; drag a point in both axes (between its neighbours, input / output readout, one undo step per drag); drag empty space to add and drag; double-click removes; no curve presets (linear / medium / strong) |
 | LR-EDIT-LIGHT-CURVE-RGB | Per-channel curves | P0 | ✅ | `cmd:develop.curve` (`channel`) | |
 | LR-EDIT-LIGHT-CURVE-REFINESAT | Curve saturation compensation | P1 | ✅ | `ctl:curve.refineSaturation` | |
 | LR-EDIT-LIGHT-CURVE-TAT | Drag-on-image curve adjust | P1 | ✅ | `cmd:develop.targeted` (`target: curve`) | |