From 2683b8dfed9d3eb6bd00640aafedf74862115b26 Mon Sep 17 00:00:00 2001
From: lillith <35337584+0xlillith@users.noreply.github.com>
Date: Sun, 11 Oct 2026 00:58:49 +0200
Subject: [PATCH] fix: allow horizontal and vertical alignment of sketch points

---
 crates/ui-egui/src/tools.rs             | 29 +++++++-
 crates/ui-egui/tests/point_alignment.rs | 90 +++++++++++++++++++++++++
 docs/book/src/guide/sketching.md        |  4 ++
 3 files changed, 121 insertions(+), 2 deletions(-)
 create mode 100644 crates/ui-egui/tests/point_alignment.rs

diff --git a/crates/ui-egui/src/tools.rs b/crates/ui-egui/src/tools.rs
index adbefac1..a2a68433 100644
--- a/crates/ui-egui/src/tools.rs
+++ b/crates/ui-egui/src/tools.rs
@@ -14,6 +14,8 @@ pub enum Kind {
     Draw(usize),
     /// Pick sketch entities; `n` picks run the command.
     Pick(usize),
+    /// Pick one straight line, or two distinct points to align.
+    HorizontalVertical,
     Dimension,
     /// A tool from `sketch_tools` (it handles its own clicks).
     Ext,
@@ -56,7 +58,7 @@ impl Tool {
             "sketch.slot.overall" => ("sketch.slot.overall", Kind::Draw(3)),
             "sketch.point" => ("sketch.point", Kind::Draw(1)),
             "sketch.dimension" => ("sketch.dimension", Kind::Dimension),
-            "sketch.constraint.horizontal_vertical" => ("sketch.constraint.horizontal_vertical", Kind::Pick(1)),
+            "sketch.constraint.horizontal_vertical" => ("sketch.constraint.horizontal_vertical", Kind::HorizontalVertical),
             "sketch.constraint.fix" => ("sketch.constraint.fix", Kind::Pick(1)),
             "sketch.constraint.coincident" => ("sketch.constraint.coincident", Kind::Pick(2)),
             "sketch.constraint.tangent" => ("sketch.constraint.tangent", Kind::Pick(2)),
@@ -93,6 +95,7 @@ pub fn hint(id: &str) -> String {
         "sketch.arc.three_point" => "Arc: click start, end, then a point on the arc".into(),
         "sketch.arc.center_point" => "Arc: click centre and start, then click end or type a signed sweep".into(),
         "sketch.dimension" => "Dimension: pick one or two entities, then click to place the value".into(),
+        "sketch.constraint.horizontal_vertical" => "Horizontal/Vertical: pick a line or two points to align".into(),
         "sketch.slot.center_to_center" | "sketch.slot.overall" => "Slot: click both ends, then the width".into(),
         _ if id.starts_with("sketch.constraint.") => "Constraint: pick the sketch entities".into(),
         _ => crate::sketch_tools::hint(id).unwrap_or_else(|| "Click in the sketch".into()),
@@ -143,6 +146,29 @@ pub fn on_click(app: &mut SolveApp, proj: &Proj, pos: Pos2) {
                 return;
             }
         }
+        Kind::HorizontalVertical => {
+            let hits = pick(app, proj, pos);
+            let hit = hits.iter().find(|hit| match hit {
+                Hit::SketchPoint { sketch, .. } | Hit::SketchCurve { sketch, .. } => Some(*sketch) == app.session.active_sketch,
+                _ => false,
+            });
+            match hit {
+                Some(Hit::SketchPoint { id, .. }) => {
+                    if let Some(first) = tool.picks.first() {
+                        if first != id {
+                            let _ = app.run(tool.cmd, json!({"points": [first, id]}));
+                            tool.picks.clear();
+                        }
+                    } else {
+                        tool.picks.push(id.clone());
+                    }
+                }
+                Some(Hit::SketchCurve { id, straight: true, .. }) if tool.picks.is_empty() => {
+                    let _ = app.run(tool.cmd, json!({"line": id}));
+                }
+                _ => {}
+            }
+        }
         Kind::Pick(n) => {
             let hits = pick(app, proj, pos);
             if let Some(id) = hits.iter().find_map(|h| match h {
@@ -292,7 +318,6 @@ fn run_shape(app: &mut SolveApp, t: &Tool) -> Result<Vec<String>, String> {
 fn run_pick(app: &mut SolveApp, t: &Tool) {
     let k = &t.picks;
     let params = match t.cmd {
-        "sketch.constraint.horizontal_vertical" => json!({"line": k[0]}),
         "sketch.constraint.fix" => json!({"entity": k[0]}),
         "sketch.constraint.coincident" => json!({"a": k[0], "b": k[1]}),
         "sketch.constraint.midpoint" => json!({"point": k[0], "line": k[1]}),
diff --git a/crates/ui-egui/tests/point_alignment.rs b/crates/ui-egui/tests/point_alignment.rs
new file mode 100644
index 00000000..45c6e126
--- /dev/null
+++ b/crates/ui-egui/tests/point_alignment.rs
@@ -0,0 +1,90 @@
+//! Horizontal/Vertical accepts either one line or two distinct sketch points.
+
+use serde_json::json;
+use solvecraft_engine::sketch::ConstraintKind;
+use solvecraft_ui_egui::scenario::Harness;
+
+#[test]
+fn horizontal_vertical_aligns_origin_and_circle_center() {
+    for (center, horizontal) in [([20.0, 3.0], true), ([3.0, 20.0], false)] {
+        for origin_first in [true, false] {
+            let mut h = Harness::new();
+            h.run(&json!([
+                {"call":"engine.execute","params":{"command":"sketch.create","params":{"plane":"XY"}}},
+                {"call":"engine.execute","params":{"command":"sketch.circle.center","params":{"center":center,"radius":5}}},
+                {"call":"ui.view","params":{"view":"top"}},
+                {"start":"sketch.constraint.horizontal_vertical"}
+            ]))
+            .unwrap();
+            let (first, second) = if origin_first { ([0.0, 0.0], center) } else { (center, [0.0, 0.0]) };
+            let undo = h.app.session.undo.len();
+            h.run(&json!([{"click":{"sketch":first}}, {"expect":{"errors":0}}])).unwrap();
+            assert_eq!(h.app.tool.as_ref().unwrap().picks.len(), 1);
+            assert!(!h.app.status.as_ref().is_some_and(|(_, _, error)| *error));
+            assert_eq!(h.app.session.undo.len(), undo);
+            // Repeating the first point must not complete a self-constraint.
+            h.run(&json!([{"click":{"sketch":first}}, {"click":{"sketch":second}}, {"expect":{"errors":0}}])).unwrap();
+            let aligned = |h: &Harness| {
+                let sk = &h.app.session.model.state().sketches[0].sketch;
+                let p = sk.point(sk.resolve_point("c1.center").unwrap()).unwrap();
+                if horizontal { p.y } else { p.x }
+            };
+            assert!(aligned(&h).abs() < 1e-6);
+            let sk = &h.app.session.model.state().sketches[0].sketch;
+            assert!(sk.constraints.iter().any(|c| if horizontal {
+                matches!(c.kind, ConstraintKind::HorizontalPoints { .. })
+            } else {
+                matches!(c.kind, ConstraintKind::VerticalPoints { .. })
+            }));
+            assert_eq!(h.app.session.undo.len(), undo + 1);
+            assert!(h.app.tool.as_ref().unwrap().picks.is_empty());
+            h.run(&json!([{"call":"engine.execute","params":{"command":"edit.undo","params":{}}}])).unwrap();
+            assert!((aligned(&h) - 3.0).abs() < 1e-6);
+            h.run(&json!([{"call":"engine.execute","params":{"command":"edit.redo","params":{}}}])).unwrap();
+            assert!(aligned(&h).abs() < 1e-6);
+        }
+    }
+}
+
+#[test]
+fn horizontal_vertical_still_accepts_one_line() {
+    let mut h = Harness::new();
+    h.run(&json!([
+        {"call":"engine.execute","params":{"command":"sketch.create","params":{"plane":"XY"}}},
+        {"call":"engine.execute","params":{"command":"sketch.line","params":{"points":[[10,10],[40,13]],"infer":false}}},
+        {"call":"ui.view","params":{"view":"top"}},
+        {"start":"sketch.constraint.horizontal_vertical"},
+        {"click":{"sketch":[25,11.5]}},
+        {"expect":{"errors":0}}
+    ]))
+    .unwrap();
+    let sk = &h.app.session.model.state().sketches[0].sketch;
+    assert!(sk.constraints.iter().any(|c| matches!(c.kind, ConstraintKind::Horizontal { .. })));
+    let a = sk.point(sk.resolve_point("l1.start").unwrap()).unwrap();
+    let b = sk.point(sk.resolve_point("l1.end").unwrap()).unwrap();
+    assert!((a.y - b.y).abs() < 1e-6);
+}
+
+#[test]
+fn horizontal_vertical_ignores_curves_and_cancels_a_pending_point() {
+    let mut h = Harness::new();
+    h.run(&json!([
+        {"call":"engine.execute","params":{"command":"sketch.create","params":{"plane":"XY"}}},
+        {"call":"engine.execute","params":{"command":"sketch.circle.center","params":{"center":[20,3],"radius":5}}},
+        {"call":"ui.view","params":{"view":"top"}},
+        {"start":"sketch.constraint.horizontal_vertical"},
+        {"click":{"sketch":[25,3]}}
+    ]))
+    .unwrap();
+    assert!(h.app.tool.as_ref().unwrap().picks.is_empty());
+    assert!(!h.app.status.as_ref().is_some_and(|(_, _, error)| *error));
+    let undo = h.app.session.undo.len();
+    h.run(&json!([{"click":{"sketch":[0,0]}}, {"click":{"sketch":[25,3]}}])).unwrap();
+    assert_eq!(h.app.tool.as_ref().unwrap().picks.len(), 1);
+    h.run(&json!([{"key":"Escape"}])).unwrap();
+    assert!(h.app.tool.is_none());
+    assert_eq!(h.app.session.undo.len(), undo);
+    let sk = &h.app.session.model.state().sketches[0].sketch;
+    let p = sk.point(sk.resolve_point("c1.center").unwrap()).unwrap();
+    assert!((p.y - 3.0).abs() < 1e-6);
+}
diff --git a/docs/book/src/guide/sketching.md b/docs/book/src/guide/sketching.md
index de24f0d4..38b908ab 100644
--- a/docs/book/src/guide/sketching.md
+++ b/docs/book/src/guide/sketching.md
@@ -54,6 +54,10 @@ fresh link once the source is available; their stored point values are preserved
 
 ## Constraints and dimensions
 
+**Horizontal/Vertical** accepts a click on a line or clicks on two distinct sketch points,
+including the origin, endpoints and circle centres. For two points, it chooses horizontal
+or vertical alignment from their current positions. Esc cancels a pending first point.
+
 The solver is SolveCraft's own (damped Gauss–Newton with degree-of-freedom analysis). Constraints:
 coincident, horizontal/vertical, parallel, perpendicular, tangent, equal, concentric, collinear,
 midpoint, symmetry, fix, curvature (G2) and polygon. **Sketch Dimension** (D) adds linear,