Cover imported STEP colours through edits and round trips

crates/engine/src/tests.rs

@@ -2051,6 +2051,67 @@ fn appearances_survive_later_features() {
     let _ = std::fs::remove_dir_all(&dir);
 }
 
+/// The original #2 RGB import acceptance, including later topology and placement edits.
+#[test]
+fn imported_rgb_appearances_survive_edits_reopen_and_step_export() {
+    let dir = std::env::temp_dir().join(format!("solvecraft-imported-rgb-{}", std::process::id()));
+    std::fs::create_dir_all(&dir).unwrap();
+    let input = dir.join("rgb.step");
+    let saved = dir.join("edited.solvecraft");
+    let output = dir.join("edited.step");
+    let mut source = Session::default();
+    for (name, x, color) in [("Red", 0, "#ff0000"), ("Green", 40, "#00ff00"), ("Blue", 80, "#0000ff")] {
+        run(&mut source, "solid.box", json!({"corner":[x,0,0],"length":30,"width":20,"height":20,"body_name":name}));
+        run(&mut source, "appearance.assign", json!({"bodies":[name],"color":color}));
+    }
+    run(&mut source, "appearance.assign", json!({"faces":[[15,10,20]],"color":"#ffff00"}));
+    run(&mut source, "file.export", json!({"path":input}));
+    let check = |session: &Session| {
+        let state = session.model.state();
+        assert_eq!(state.bodies.len(), 3);
+        for (name, color) in [("Red", [1., 0., 0.]), ("Green", [0., 1., 0.]), ("Blue", [0., 0., 1.])] {
+            let body = state.body(name).unwrap();
+            assert_eq!(session.doc.body_color(body), Some(color), "{name} retains its imported body colour");
+        }
+        let red = state.body("Red").unwrap();
+        assert!(session.doc.face_colors(red).iter().any(|(_, look)| look.color == [255, 255, 0]), "Red retains its yellow top face");
+        assert!(session.model.results.iter().all(|result| result.error.is_none()));
+    };
+    let mut edited = Session::default();
+    run(&mut edited, "doc.open", json!({"path":input}));
+    check(&edited);
+    let initial_volume = volume(&mut edited);
+    run(&mut edited, "solid.fillet", json!({"bodies":["Red"],"edges":[[0,10,20]],"radius":2}));
+    check(&edited);
+    run(&mut edited, "solid.move", json!({"bodies":["Red"],"translate":[0,0,5]}));
+    check(&edited);
+    run(&mut edited, "solid.box", json!({"corner":[85,5,15],"length":10,"width":10,"height":10,"body_name":"Cutter"}));
+    run(&mut edited, "solid.combine", json!({"target":"Blue","tools":["Cutter"],"operation":"cut"}));
+    check(&edited);
+    run(&mut edited, "solid.box", json!({"corner":[65,0,0],"length":10,"width":20,"height":20,"body_name":"Joiner"}));
+    run(&mut edited, "solid.combine", json!({"target":"Green","tools":["Joiner"],"operation":"join"}));
+    check(&edited);
+    let edited_volume = volume(&mut edited);
+    // The join adds 5*20*20, the pocket removes 10*10*5, and the
+    // radius-2 quarter-round replaces a 2*2 square along a 20 mm edge.
+    let expected_volume = initial_volume + 2000. - 500. - (4. - PI) * 20.;
+    assert!((edited_volume - expected_volume).abs() < 0.1, "{edited_volume} vs {expected_volume}");
+    run(&mut edited, "edit.undo", json!({}));
+    run(&mut edited, "edit.redo", json!({}));
+    check(&edited);
+    run(&mut edited, "file.save_as", json!({"path":saved}));
+    let mut reopened = Session::default();
+    run(&mut reopened, "doc.open", json!({"path":saved}));
+    check(&reopened);
+    assert!(rel(volume(&mut reopened), edited_volume) < 1e-8);
+    run(&mut reopened, "file.export", json!({"path":output}));
+    let mut roundtrip = Session::default();
+    run(&mut roundtrip, "doc.open", json!({"path":output}));
+    check(&roundtrip);
+    assert!(rel(volume(&mut roundtrip), edited_volume) < 1e-3);
+    let _ = std::fs::remove_dir_all(dir);
+}
+
 /// Extrude To Object (a parallel face, with an offset; a slanted face) and From Object.
 #[test]
 fn extrude_to_and_from_objects() {

docs/step-import.md

@@ -8,6 +8,19 @@ SolidCraft reads STEP (ISO 10303-21; AP203, AP214 and AP242 geometry) with its o
 
 Read: manifold solid breps (with voids), faceted breps, shell-based surface models; planes, cylinders, cones, spheres, tori, B-spline and rational B-spline surfaces (with knots, Bézier, uniform, quasi-uniform), surfaces of revolution and linear extrusion, trimmed surfaces; lines, circles, ellipses, B-spline curves, polylines, trimmed/surface/seam curves; length and angle units (SI prefixes, conversion-based units such as inches); product names (body names come from the solid's name, else the product's); surface colours; assemblies (next-assembly-usage occurrences placed by item-defined transformations, and mapped items) — the product tree is kept in the feature for the components milestone. Files are untrusted: sizes, entity counts and nesting are capped and every kernel call is guarded. What cannot be read becomes a warning on the feature (a face left out gives an open body); not read yet: offset surfaces, pcurve-only edges.
 
+## Imported appearances
+
+Imported body colours and face colours are retained through later features. Body
+colours remain the fallback under explicit design appearances and materials; face
+colours follow persistent face names. A removed face has no colour assignment to
+display on the resulting body.
+
+The RGB import regression in the engine checks a STEP file with separate red,
+green and blue bodies: fillet and move the red body, cut the blue body, join an
+extension to the green body, undo/redo,
+save and reopen the design, then export and reopen STEP. It checks all three body
+colours and the red body's separately coloured top face at each stage.
+
 ## IGES
 
 IGES 5.3 files (`.igs`/`.iges`) open, insert and drop the same way: `crates/kernel/src/iges_in.rs` (written from the published specification) restates the file as STEP and the STEP reader reads it, so the feature holds STEP text. Read: manifold solid B-reps (186) with their shells, faces, loops, edge and vertex lists; trimmed (144) and bounded (143) surfaces, and bare B-spline patches, sewn into a solid by their shared edges (an open body when they do not close); lines, circular arcs, ellipses, composite curves, rational B-spline curves; planes (108, 190), cylinders, cones, spheres, tori, rational B-spline surfaces, surfaces of revolution and tabulated cylinders; transformation matrices; units; colours (314 and the predefined numbers); body names (name properties, else labels). Not read yet: ruled and offset surfaces, curves on surfaces given only in parameter space. Export (`file.export` to `.igs`) writes each body as a manifold solid B-rep on the same surfaces a STEP export uses, with its name and colour.