Point handles for routes and outlines; Area corners; bus goes round right

Studio: one selected object with pts (a route, an outlined area) shows a
handle on each point and a + in the middle of each side: drag a point to
move it, drag a + to add one there, double-click a point to remove it
(open routes keep 2, outlines 3). Points snap to the grid and onto wall,
fence and road ends, at any angle; one undo step each. Handles keep their
screen size (new viewer callback onView on every redraw) and follow
re-renders and selection. The viewer captures the pointer, so a double-
click targets the drawing: the last point pressed is remembered instead.

Prefab meta `outline`: the prefab draws pts as its outline. Area has it:
Edit corners turns its rectangle into four points, Rectangle again
removes them.

Routes: where a path doubles back, the lane offset puts a point on each
side, so it rounds into a U-turn instead of a diagonal across the lanes.
The streets demo bus now runs east, three quarters round the roundabout
(clockwise, left-hand traffic), down south street, turns and comes back
by the short way, instead of going round the wrong way on its way out.

Tests: Rust 81 (a doubling-back route: each mover once, no sort cycles),
Studio 134 (corners, move, add, remove, undo), web 100.

crates/isokit-script/src/doc.rs

@@ -155,6 +155,10 @@ pub struct PrefabMeta {
     /// Studio puts one in each corner of a run drawn corner by corner.
     #[serde(default, skip_serializing_if = "String::is_empty")]
     pub corner: String,
+    /// The prefab draws the object's `pts` as its outline when it has them (areas):
+    /// the Studio offers to turn its rectangle into corners that can be dragged.
+    #[serde(default, skip_serializing_if = "is_false")]
+    pub outline: bool,
     #[serde(default)]
     pub props: Vec<PropDef>,
     /// Module the prefab comes from ("isokit/site", "lib/kiosk.rhai").

crates/isokit-script/src/tests.rs

@@ -936,8 +936,24 @@ fn route_movers_show_once_each_at_every_moment() {
     );
     deer.rot = 30.0;
     deer.pts = Some(vec![[-6.0, 0.0], [6.0, 0.0]]);
+    // a loop that doubles back twice (a spur up to a stop and back, a U-turn at the west end):
+    // each way keeps to its side, so the strips never overlap
+    let mut spur = obj(
+        "spur",
+        "route",
+        0.0,
+        40.0,
+        json!({"kind": "bus", "n": 2, "closed": true}),
+    );
+    spur.pts = Some(vec![[-20.0, 0.0], [20.0, 0.0], [20.0, 15.0], [20.0, 0.0]]);
     let doc = Doc {
-        objects: vec![cars, walk, deer, obj("t1", "tree", 0.0, -14.0, json!({}))],
+        objects: vec![
+            cars,
+            walk,
+            deer,
+            spur,
+            obj("t1", "tree", 0.0, -14.0, json!({})),
+        ],
         ..Default::default()
     };
     for view in 0..4u8 {
@@ -947,7 +963,7 @@ fn route_movers_show_once_each_at_every_moment() {
         assert_eq!(out.cycles, 0, "view {view}: depth-sort cycles");
         // one <style> with every keyframe set, each used
         assert_eq!(out.html.matches("<style>").count(), 1);
-        for (id, n) in [("cars", 4), ("walk", 3), ("deer", 2)] {
+        for (id, n) in [("cars", 4), ("walk", 3), ("deer", 2), ("spur", 2)] {
             let wins = travel_windows(&b, id);
             assert!(!wins.is_empty(), "{id}");
             // at any moment, each mover is on exactly one piece

crates/isokit-script/stdlib/ground.rhai

@@ -26,8 +26,8 @@ fn prefab_site(o) {
 }
 
 fn meta_area() {
-    #{ label: "Area", category: "Ground", icon: "▱", shape: "rect",
-       help: "A paved or planted area lying on the ground.",
+    #{ label: "Area", category: "Ground", icon: "▱", shape: "rect", outline: true,
+       help: "A paved or planted area lying on the ground. Edit corners turns the rectangle into points you can drag, add (drag a +) and remove (double-click), for any outline.",
        props: [
          #{ key: "w", type: "float", def: 10.0, min: 0.5, max: 1000.0, step: 0.5, label: "Width (m)" },
          #{ key: "d", type: "float", def: 6.0, min: 0.5, max: 1000.0, step: 0.5, label: "Depth (m)" },

crates/isokit-script/stdlib/routes.rhai

@@ -84,7 +84,8 @@ fn route_pts(o, closed) {
     out
 }
 
-/// The line `d` metres to the left of a path (mitred corners).
+/// The line `d` metres to the left of a path (mitred corners). Where the path
+/// doubles back, the offset line gets a point on each side: a U-turn once rounded.
 fn rt_offset(pts, d, closed) {
     if d == 0.0 { return pts; }
     let n = pts.len();
@@ -97,8 +98,12 @@ fn rt_offset(pts, d, closed) {
         if type_of(n1) == "()" { n1 = n2; }
         if type_of(n2) == "()" { n2 = n1; }
         let s = 1.0 + n1[0] * n2[0] + n1[1] * n2[1];
-        let m = if s < 0.3 { n2 } else { rt_mul(rt_add(n1, n2), 1.0 / s) };
-        out.push(rt_add(pts[i], rt_mul(m, d)));
+        if s < 0.3 {
+            out.push(rt_add(pts[i], rt_mul(n1, d)));
+            out.push(rt_add(pts[i], rt_mul(n2, d)));
+        } else {
+            out.push(rt_add(pts[i], rt_mul(rt_mul(rt_add(n1, n2), 1.0 / s), d)));
+        }
     }
     out
 }