Layouts: a viewport on a frozen layer hides its contents (fixes #395) (#396)

Freezing a viewport's own layer hid only its border; the model space
seen through it still showed on screen and in plots. As in AutoCAD, a
frozen viewport layer now hides the contents too, while turning the
layer off still hides only the border. The check is in the shared
layout path, so display, PDF/SVG/PNG export and plotting agree.

Co-authored-by: Claude Opus 5.5 <[email protected]>

crates/render/src/lib.rs

@@ -316,6 +316,10 @@ fn viewport(b: &mut Builder, d: &Drawing, e: &Entity, vp: &cadcraft_doc::Viewpor
     if vp.id == 1 || !e.common.visible {
         return;
     }
+    // The viewport's layer frozen hides its contents too (layer off hides only the border).
+    if d.layer(&e.common.layer).is_some_and(|l| l.frozen) {
+        return;
+    }
     // Border (on the viewport's layer; layer off hides only the border).
     entity(b, &top_ctx(d, Mat3::IDENTITY, e.handle, &[], &[]), e);
     if b.list.expanded >= MAX_BLOCK_EXPANSION {

crates/render/tests/viewport_frozen_layer.rs

@@ -0,0 +1,44 @@
+//! A layout viewport whose own layer is frozen shows neither its border nor its contents, on
+//! screen and when plotting; turned off, the layer hides only the border (issue #395).
+
+use cadcraft_doc::{Circle, Common, Drawing, EntityKind, Space, Viewport};
+use cadcraft_geom::{Vec2, Vec3};
+use cadcraft_render::{DisplayList, Options, VIEWPORT_CONTENT, build, build_plot};
+
+fn drawing() -> Drawing {
+    let mut d = Drawing::new_imperial();
+    d.add(&Space::Model, Common::default(), EntityKind::Circle(Circle { center: Vec3::ZERO, radius: 5.0 })).unwrap();
+    d.ensure_layer("VPORTS");
+    let vp = Viewport {
+        center: Vec3::new(5.0, 4.0, 0.0),
+        width: 8.0,
+        height: 6.0,
+        view_center: Vec2::ZERO,
+        view_height: 12.0,
+        id: 2,
+        locked: false,
+        frozen_layers: Vec::new(),
+        layer_colors: Vec::new(),
+    };
+    d.add(&Space::Paper("Layout1".into()), Common { layer: "VPORTS".into(), ..Default::default() }, EntityKind::Viewport(vp)).unwrap();
+    d
+}
+
+/// (contents drawn, border drawn) on screen and in a plot.
+fn shown(d: &Drawing) -> [(bool, bool); 2] {
+    let space = Space::Paper("Layout1".into());
+    let parts = |l: DisplayList| (l.prims.iter().any(|p| p.handle == VIEWPORT_CONTENT), l.prims.iter().any(|p| p.handle != VIEWPORT_CONTENT));
+    [parts(build(d, &space, &Options::default())), parts(build_plot(d, &space, &Options::default()))]
+}
+
+#[test]
+fn frozen_viewport_layer_hides_the_contents_off_only_the_border() {
+    let mut d = drawing();
+    assert_eq!(shown(&d), [(true, true); 2]);
+    d.layer_mut("VPORTS").unwrap().on = false;
+    assert_eq!(shown(&d), [(true, false); 2], "off: contents stay, border hidden");
+    let l = d.layer_mut("VPORTS").unwrap();
+    l.on = true;
+    l.frozen = true;
+    assert_eq!(shown(&d), [(false, false); 2], "frozen: contents hidden too");
+}