Isolation mode: double-clicking a single object isolates it

With Double Click To Isolate on, the Selection tool isolated groups only. A
double-click on a single path, compound path, image, mesh or placed file now
isolates it too, as the public documentation describes. Type still switches to
the Type tool; blends, envelopes, repeats and symbol instances keep their own
editing modes.

While a single object is isolated only it is hit, marqueed and taken by Select
All, new art goes beside it in its group or layer, and a double-click on the
empty canvas leaves with it selected. object.isolate accepts any object except
type.

crates/tools/src/corners.rs

@@ -632,7 +632,10 @@ mod tests {
         let cx2 = cx(&d, &whole, &p);
         let a = crate::create("selection").pointer(&cx2, &PointerEvent::new(PointerKind::DoubleClick, 190.0, 110.0));
         assert_eq!(a, vec![Action::Dialog(DIALOG.into(), json!({"id": id.0, "corners": [0, 1, 2, 3]}))]);
-        assert!(crate::create("selection").pointer(&cx2, &PointerEvent::new(PointerKind::DoubleClick, 150.0, 150.0)).is_empty());
+        // Off the widgets, the Selection tool's double-click isolates the shape (Double Click To
+        // Isolate) instead.
+        let a = crate::create("selection").pointer(&cx2, &PointerEvent::new(PointerKind::DoubleClick, 150.0, 150.0));
+        assert_eq!(a, vec![Action::Exec("object.isolate".into(), json!({"id": id.0}))]);
     }
 
     /// Hide Corner Widget for angles greater than (#394): a rectangle's right angles hide below

crates/tools/src/select.rs

@@ -3,8 +3,8 @@
 //! Guides, or with them off View › Snap to Point, snap it),
 //! bounding-box scale (Shift proportional, Alt from centre) and rotate (outside corners, Shift 45°),
 //! drag a live rectangle's or polygon's corner widget to round its corners (Alt-click cycles their kind,
-//! double-click opens the Corners dialog), double-click to enter isolation mode (Double Click To
-//! Isolate), Cmd/Ctrl-click to select the object behind (Command Click to Select Objects Behind),
+//! double-click opens the Corners dialog), double-click a group or an object to enter isolation
+//! mode (Double Click To Isolate), Cmd/Ctrl-click to select the object behind (Command Click to Select Objects Behind),
 //! click or drag a ruler guide ([`crate::rulerguide`]), drag the brackets of type on a path
 //! ([`crate::pathtype`]), double-click the type widget to convert point type to area type and back
 //! ([`crate::typewidget`]).
@@ -260,12 +260,19 @@ impl Tool for SelectionTool {
                 }
                 if let Some(h) = hit_test(cx.doc, p, cx.hit_options()) {
                     let top = h.top_object(cx.isolation);
-                    if cx.double_click_isolate && cx.doc.node(top).is_some_and(|n| matches!(n.kind, vectorcraft_doc::NodeKind::Group { .. })) {
-                        return vec![Action::Exec("object.isolate".into(), json!({ "id": top.0 }))];
-                    }
                     if cx.doc.node(top).is_some_and(|n| matches!(n.kind, vectorcraft_doc::NodeKind::Text(_))) {
                         return vec![Action::SwitchTool("type".into())];
                     }
+                    // A group, a compound path or a single path, image, mesh or placed file, not
+                    // the one already isolated. Blends, envelopes, repeats and symbol instances
+                    // aren't: they have editing modes of their own.
+                    use vectorcraft_doc::NodeKind as K;
+                    let isolates = cx.doc.node(top).is_some_and(|n| {
+                        matches!(n.kind, K::Group { .. } | K::Compound { .. } | K::Path { .. } | K::Image(_) | K::Mesh(_) | K::PlacedDocument(_))
+                    });
+                    if cx.double_click_isolate && isolates && cx.isolation != Some(top) {
+                        return vec![Action::Exec("object.isolate".into(), json!({ "id": top.0 }))];
+                    }
                 } else if cx.isolation.is_some() {
                     return vec![Action::Exec("object.exitIsolation".into(), json!({}))];
                 }