App: store constraints

Draft listing of constraints in outline view.

app-proto/sketch-outline/src/assembly.rs

@@ -1,4 +1,5 @@
 use nalgebra::DVector;
+use rustc_hash::FxHashSet;
 use slab::Slab;
 use sycamore::reactive::Signal;
 
@@ -7,11 +8,18 @@ pub struct Element {
     pub id: String,
     pub label: String,
     pub color: [f32; 3],
-    pub rep: DVector<f64>
+    pub rep: DVector<f64>,
+    pub constraints: FxHashSet<usize>
+}
+
+pub struct Constraint {
+    pub args: (usize, usize),
+    pub rep: f64
 }
 
 // a complete, view-independent description of an assembly
 #[derive(Clone)]
 pub struct Assembly {
-    pub elements: Signal<Slab<Element>>
+    pub elements: Signal<Slab<Element>>,
+    pub constraints: Signal<Slab<Constraint>>
 }