Page Setup: report unsupported layout plot areas as not available yet (#491) (#597)

Squash of PR #597 by @MarekSpodBiedry.

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

crates/engine/src/cmd/layout.rs

@@ -704,6 +704,10 @@ fn run_pagesetup(s: &mut Session, p: &Value) -> Result<Value> {
         if !["layout", "extents", "display", "window", "limits"].contains(&v.as_str()) {
             return Err(bad(cmd, "`plotArea` must be layout, extents, display, window or limits"));
         }
+        // Layout plotting always prints the whole sheet; the other areas are only stored for DXF round trips.
+        if v != "layout" && v != page.plot_area {
+            return Err(bad(cmd, format!("plot area `{v}` is not available yet; layouts plot the whole sheet (`layout`)")));
+        }
         page.plot_area = v;
     }
     if let Some(v) = str_param(p, "plotStyleTable") {
@@ -1016,6 +1020,12 @@ mod tests {
         assert!(s.execute("pagesetup", &json!({"layout": "Layout1", "margins": [1, 2]})).is_err());
         assert!(s.execute("pagesetup", &json!({"layout": "Layout1", "width": 1e308, "height": 5})).is_err());
         assert!(s.execute("pagesetup", &json!({"paper": "A4"})).is_err(), "model tab needs a layout");
+        for area in ["extents", "display", "window", "limits"] {
+            let e = s.execute("pagesetup", &json!({"layout": "Layout1", "plotArea": area})).unwrap_err();
+            assert!(e.to_string().contains("not available yet"), "{area}: {e}");
+        }
+        let r = s.execute("pagesetup", &json!({"layout": "Layout1", "plotArea": "Layout"})).unwrap();
+        assert_eq!(r["page"]["plotArea"], "layout");
         let report = s.execute("pagesetup", &Value::Null).unwrap();
         assert!(report["papers"].as_array().unwrap().len() >= 10);
         s.execute("pagesetup", &json!({"layout": "Layout2", "width": 500, "height": 300})).unwrap();

crates/ui-egui/src/managers.rs

@@ -501,7 +501,8 @@ fn page_setup(app: &mut CadApp, ctx: &egui::Context, open: &mut bool) -> Action
             });
             let Some((_, name, page)) = layouts.iter().find(|l| l.1 == sel) else { return };
             right.label(RichText::new(format!("Page setup of {name}")).strong());
-            let rows = PageRows { areas: &["layout", "extents", "display", "limits"], scale: true, center: true };
+            // Layout plotting always prints the whole sheet, so only that area is offered.
+            let rows = PageRows { areas: &["layout"], scale: true, center: true };
             egui::Grid::new("pagesetup_grid").num_columns(2).spacing(vec2(10.0, 6.0)).show(right, |ui| {
                 if let Some((k, v)) = page_rows(ui, egui::Id::new(("pagesetup", name)), page, &rows) {
                     action = Some(("pagesetup", json!({ "layout": name, k: v })));