Sketch: the first dimension scales a sketch drawn by eye (#1365) (#1416)

* Sketch: the first dimension scales a sketch drawn by eye (#1365)

Lines drawn by eye have no size of their own until a dimension gives them one, but the first
dimension kept every other drawn length and distorted the sketch to fit (a free construction
line through the origin turned instead of the shape moving). The dimension tool now scales
the whole sketch about its origin to the first length dimension, as long as nothing in the
sketch fixes a size yet: no other driving length dimension, nothing fixed, projected or
patterned. Every geometric constraint and angle holds on the scaled sketch. Later
dimensions size what they measure as before; sketch.dimension does this only with
scale_sketch: true, so scripts are unchanged.

Fixes #1365

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Scenario s01: dimension the box's height too, now that the first dimension scales the sketch

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/sketch_ux_tests.rs

@@ -1468,3 +1468,59 @@ fn a_live_drag_shares_one_decomposition_budget() {
     assert!(d.count > 6, "{d:?}");
     assert!(d.work <= budget + one.work, "{d:?} over a budget of {budget}");
 }
+
+/// #1365: lines drawn by eye and a construction line through the origin, as in the report.
+fn drawn_by_eye() -> Session {
+    let mut s = new_sketch();
+    run(&mut s, "sketch.line", json!({"points": [[-56.7, 0], [56.7, 0]], "construction": true, "ids": ["hc"]}));
+    run(&mut s, "sketch.constraint.coincident", json!({"a": "origin", "b": "hc"}));
+    run(&mut s, "sketch.line", json!({"points": [[0, -54], [0, 55.2]], "construction": true, "ids": ["vc"]}));
+    run(&mut s, "sketch.constraint.coincident", json!({"a": "origin", "b": "vc"}));
+    run(
+        &mut s,
+        "sketch.line",
+        json!({"points": [[0, 26], [29.6, 26], [29.6, 41.2], [44, 41.2], [44, 0]], "infer": true, "ids": ["a", "b", "c", "d"]}),
+    );
+    run(&mut s, "sketch.constraint.coincident", json!({"a": "a.start", "b": "vc"}));
+    run(&mut s, "sketch.constraint.coincident", json!({"a": "d.end", "b": "hc"}));
+    s
+}
+
+#[test]
+fn the_first_dimension_scales_a_sketch_drawn_by_eye() {
+    let mut s = drawn_by_eye();
+    let before = sketch(&s);
+    let out = run(&mut s, "sketch.dimension", json!({"entities": ["vc", "b"], "value": "50 mm", "text_at": [15, 47], "scale_sketch": true}));
+    let f = 50.0 / 29.6;
+    assert!((out["scaled"].as_f64().unwrap() - f).abs() < 1e-6, "{out}");
+    assert!((out["measured"].as_f64().unwrap() - 50.0).abs() < 1e-6, "{out}");
+    // Every point scaled about the origin: the shape and the construction lines keep their
+    // directions (the vertical construction line stays vertical), only the size changes.
+    let after = sketch(&s);
+    for (p, q) in before.points.iter().zip(&after.points) {
+        assert!(q.pos.dist(p.pos * f) < 1e-6, "{} {:?} -> {:?}", p.id, p.pos, q.pos);
+    }
+    // The second dimension sizes the sketch as usual: nothing scales again.
+    let out = run(&mut s, "sketch.dimension", json!({"entities": ["c"], "value": "30 mm", "scale_sketch": true}));
+    assert!(out.get("scaled").is_none(), "{out}");
+    assert!((pt(&s, "c.end").x - pt(&s, "c.start").x - 30.0).abs() < 1e-6);
+    assert!((pt(&s, "b.start").x - pt(&s, "vc.start").x - 50.0).abs() < 1e-6);
+    // The construction line can still be made vertical (it already is: redundant, not a conflict).
+    run(&mut s, "sketch.constraint.horizontal_vertical", json!({"line": "vc"}));
+}
+
+#[test]
+fn the_first_dimension_does_not_scale_a_sketch_that_has_a_size() {
+    // A sketch with projected or fixed geometry, or another length dimension, already has a
+    // size: its first new dimension sizes what it measures as before.
+    let mut s = new_sketch();
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0": [0, 0], "p1": [60, 40]}));
+    run(&mut s, "sketch.constraint.fix", json!({"entity": "l1.end"}));
+    let out = run(&mut s, "sketch.dimension", json!({"entities": ["l2"], "value": "50 mm", "scale_sketch": true}));
+    assert!(out.get("scaled").is_none(), "{out}");
+    // An angle never scales.
+    let mut s = new_sketch();
+    run(&mut s, "sketch.line", json!({"points": [[0, 0], [30, 0], [50, 20]]}));
+    let out = run(&mut s, "sketch.dimension", json!({"entities": ["l1", "l2"], "value": "60 deg", "scale_sketch": true}));
+    assert!(out.get("scaled").is_none(), "{out}");
+}