app-proto/main.css

@@ -131,10 +131,6 @@ details[open]:has(li) .element-switch::after {
   color: var(--text-invalid);
 }
 
-.constraint > input[type=checkbox] {
-  margin: 0px 8px 0px 0px;
-}
-
 .constraint > input[type=text] {
   color: inherit;
   background-color: inherit;
@@ -154,6 +150,10 @@ details[open]:has(li) .element-switch::after {
   font-style: normal;
 }
 
+.constrained > .status::after, details:has(.constrained):not([open]) .status::after {
+  content: '🔗';
+}
+
 .invalid > .status::after, details:has(.invalid):not([open]) .status::after {
   content: '⚠';
   color: var(--text-invalid);

app-proto/src/add_remove.rs

@@ -1,7 +1,17 @@
 use sycamore::prelude::*;
 use web_sys::{console, wasm_bindgen::JsValue};
 
-use crate::{engine, AppState, assembly::{Assembly, Constraint, Element}};
+use crate::{
+    engine,
+    AppState,
+    assembly::{
+        Assembly,
+        Constraint,
+        ConstraintRole,
+        Element
+    },
+    engine::Q
+};
 
 /* DEBUG */
 // load an example assembly for testing. this code will be removed once we've
@@ -190,15 +200,23 @@ pub fn AddRemove() -> View {
                             (subject_vec[0].clone(), subject_vec[1].clone())
                         }
                     );
-                    let lorentz_prod = create_signal(0.0);
-                    let lorentz_prod_valid = create_signal(false);
-                    let active = create_signal(true);
+                    let measured = state.assembly.elements.map(
+                        move |elts| {
+                            let reps = (
+                                elts[subjects.0].representation.get_clone(),
+                                elts[subjects.1].representation.get_clone()
+                            );
+                            reps.0.dot(&(&*Q * reps.1))
+                        }
+                    );
+                    let desired = create_signal(0.0);
+                    let role = create_signal(ConstraintRole::Measure);
                     state.assembly.insert_constraint(Constraint {
                         subjects: subjects,
-                        lorentz_prod: lorentz_prod,
-                        lorentz_prod_text: create_signal(String::new()),
-                        lorentz_prod_valid: lorentz_prod_valid,
-                        active: active,
+                        measured: measured,
+                        desired: desired,
+                        desired_text: create_signal(String::new()),
+                        role: role,
                     });
                     state.selection.update(|sel| sel.clear());
                     
@@ -212,19 +230,19 @@ pub fn AddRemove() -> View {
                                 &JsValue::from(cst.subjects.0),
                                 &JsValue::from(cst.subjects.1),
                                 &JsValue::from(":"),
-                                &JsValue::from(cst.lorentz_prod.get_untracked())
+                                &JsValue::from(cst.desired.get_untracked())
                             );
                         }
                     });
                     
-                    // update the realization when the constraint becomes active
-                    // and valid, or is edited while active and valid
+                    // update the realization when the observable becomes
+                    // constrained, or is edited while constrained
                     create_effect(move || {
                         console::log_1(&JsValue::from(
                             format!("Constraint ({}, {}) updated", subjects.0, subjects.1)
                         ));
-                        lorentz_prod.track();
-                        if active.get() && lorentz_prod_valid.get() {
+                        desired.track();
+                        if role.with(|r| matches!(r, ConstraintRole::Constrain)) {
                             state.assembly.realize();
                         }
                     });

app-proto/src/assembly.rs

@@ -111,13 +111,19 @@ impl Element {
     }
 }
 
+pub enum ConstraintRole {
+    Measure,
+    Constrain,
+    Invalid
+}
+
 #[derive(Clone)]
 pub struct Constraint {
     pub subjects: (ElementKey, ElementKey),
-    pub lorentz_prod: Signal<f64>,
-    pub lorentz_prod_text: Signal<String>,
-    pub lorentz_prod_valid: Signal<bool>,
-    pub active: Signal<bool>
+    pub measured: ReadSignal<f64>,
+    pub desired: Signal<f64>,
+    pub desired_text: Signal<String>,
+    pub role: Signal<ConstraintRole>
 }
 
 // the velocity is expressed in uniform coordinates
@@ -230,11 +236,11 @@ impl Assembly {
             let mut gram_to_be = PartialMatrix::new();
             self.constraints.with_untracked(|csts| {
                 for (_, cst) in csts {
-                    if cst.active.get_untracked() && cst.lorentz_prod_valid.get_untracked() {
+                    if cst.role.with_untracked(|role| matches!(role, ConstraintRole::Constrain)) {
                         let subjects = cst.subjects;
                         let row = elts[subjects.0].column_index.unwrap();
                         let col = elts[subjects.1].column_index.unwrap();
-                        gram_to_be.push_sym(row, col, cst.lorentz_prod.get_untracked());
+                        gram_to_be.push_sym(row, col, cst.desired.get_untracked());
                     }
                 }
             });

app-proto/src/outline.rs

@@ -8,7 +8,16 @@ use web_sys::{
     wasm_bindgen::JsCast
 };
 
-use crate::{AppState, assembly, assembly::{Constraint, ConstraintKey, ElementKey}};
+use crate::{
+    AppState,
+    assembly,
+    assembly::{
+        Constraint,
+        ConstraintKey,
+        ConstraintRole::*,
+        ElementKey
+    }
+};
 
 // an editable view of the Lorentz product representing a constraint
 #[component(inline_props)]
@@ -16,16 +25,22 @@ fn LorentzProductInput(constraint: Constraint) -> View {
     view! {
         input(
             r#type="text",
-            bind:value=constraint.lorentz_prod_text,
+            placeholder=constraint.measured.with(|result| result.to_string()),
+            bind:value=constraint.desired_text,
             on:change=move |event: Event| {
                 let target: HtmlInputElement = event.target().unwrap().unchecked_into();
-                match target.value().parse::<f64>() {
-                    Ok(lorentz_prod) => batch(|| {
-                        constraint.lorentz_prod.set(lorentz_prod);
-                        constraint.lorentz_prod_valid.set(true);
-                    }),
-                    Err(_) => constraint.lorentz_prod_valid.set(false)
-                };
+                let value = target.value();
+                if value.is_empty() {
+                    constraint.role.set(Measure);
+                } else {
+                    match target.value().parse::<f64>() {
+                        Ok(desired) => batch(|| {
+                            constraint.desired.set(desired);
+                            constraint.role.set(Constrain);
+                        }),
+                        Err(_) => constraint.role.set(Invalid)
+                    };
+                }
             }
         )
     }
@@ -43,12 +58,15 @@ fn ConstraintOutlineItem(constraint_key: ConstraintKey, element_key: ElementKey)
         constraint.subjects.0
     };
     let other_subject_label = assembly.elements.with(|elts| elts[other_subject].label.clone());
-    let class = constraint.lorentz_prod_valid.map(
-        |&lorentz_prod_valid| if lorentz_prod_valid { "constraint" } else { "constraint invalid" }
+    let class = constraint.role.map(
+        |role| match role {
+            Measure => "constraint",
+            Constrain => "constraint constrained",
+            Invalid => "constraint invalid"
+        }
     );
     view! {
         li(class=class.get()) {
-            input(r#type="checkbox", bind:checked=constraint.active)
             div(class="constraint-label") { (other_subject_label) }
             LorentzProductInput(constraint=constraint)
             div(class="status")