ui: Relax around worst element at the top of Mesh Quality; plain preview text (#398)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/engine/src/cmd/relax.rs

@@ -374,7 +374,9 @@ pub(crate) fn weights(model: &Model, p: &Value) -> Result<(BTreeMap<u32, f64>, O
         nodes.extend(el.nodes.iter().copied());
     }
     if listed == 0 {
-        return Err(EngineError::Params("say which nodes to relax: give one of `center` and `radius`, `around_element`, `nodes`, `elements` or `set`".into()));
+        return Err(EngineError::Params(
+            "say which nodes to relax: give one of `center` and `radius`, `around_element`, `nodes`, `elements` or `set`".into(),
+        ));
     }
     if let Some(only) = &only {
         nodes.retain(|n| only.contains(n));
@@ -450,7 +452,7 @@ fn relax_nodes(s: &mut Session, p: &Value) -> Result<Value> {
         s.model.set_node(*n, *x)?;
     }
     let summary = format!(
-        "moved {} node{} (largest {:.3e}); scaled Jacobian min {:.3} → {:.3}{}",
+        "moved {} node{} (largest {:.3e}); scaled Jacobian min from {:.3} to {:.3}{}",
         r.moved,
         if r.moved == 1 { "" } else { "s" },
         r.max_displacement,

crates/ui-egui/src/lib.rs

@@ -1179,7 +1179,7 @@ impl ModelApp {
         let p = self.relax_preview()?;
         let r = &p.relaxed;
         Some(format!(
-            "Preview: {} nodes move (largest {:.3}); scaled Jacobian min {:.3} → {:.3}, edge ratio max {:.2} → {:.2}, {} → {} invalid",
+            "Preview: {} nodes move (largest {:.3}); scaled Jacobian min {:.3} to {:.3}, edge ratio max {:.2} to {:.2}, invalid {} to {}",
             r.moved,
             r.max_displacement,
             r.before.min_quality,

crates/ui-egui/src/reply.rs

@@ -347,7 +347,8 @@ const METRICS: [(&str, &str, bool); 4] = [
 const MAX_SELECT: usize = 10_000;
 
 /// `mesh.quality`'s reply: the counts, then each metric's range, histogram and worst element (a
-/// click selects and frames it), and buttons selecting the invalid and undetermined elements.
+/// click selects and frames it), buttons selecting the invalid and undetermined elements, and
+/// Relax around worst element (#398).
 fn quality(ui: &mut egui::Ui, t: &Tokens, v: &Value, acts: &mut Vec<Act>) {
     let n = |k: &str| v.get(k).and_then(Value::as_u64).unwrap_or(0);
     let labels = |k: &str| -> Vec<u32> {
@@ -392,6 +393,15 @@ fn quality(ui: &mut egui::Ui, t: &Tokens, v: &Value, acts: &mut Vec<Act>) {
             acts.push(Act::Elements(l));
         }
     }
+    if let Some(worst) = v.pointer("/metrics/scaled_jacobian/worst").and_then(Value::as_u64).and_then(|w| u32::try_from(w).ok()) {
+        if ui
+            .button("Relax around worst element")
+            .on_hover_text("Open Relax Nodes with its sphere round the element of smallest scaled Jacobian; preview, then OK")
+            .clicked()
+        {
+            acts.push(Act::Relax(worst));
+        }
+    }
     for (key, label, low_bad) in METRICS {
         let Some(m) = v.pointer(&format!("/metrics/{key}")).filter(|m| m.is_object()) else { continue };
         let f = |k: &str| m.get(k).and_then(Value::as_f64);
@@ -419,16 +429,6 @@ fn quality(ui: &mut egui::Ui, t: &Tokens, v: &Value, acts: &mut Vec<Act>) {
             }
         }
     }
-    if let Some(worst) = v.pointer("/metrics/scaled_jacobian/worst").and_then(Value::as_u64).and_then(|w| u32::try_from(w).ok()) {
-        ui.add_space(6.0);
-        if ui
-            .button("Relax around worst element")
-            .on_hover_text("Open Relax Nodes with its sphere round the element of smallest scaled Jacobian; preview, then OK")
-            .clicked()
-        {
-            acts.push(Act::Relax(worst));
-        }
-    }
     if let Some(skipped) = v.get("skipped").and_then(Value::as_object).filter(|s| !s.is_empty()) {
         ui.add_space(6.0);
         let text: Vec<String> = skipped.iter().map(|(k, n)| format!("{k}: {}", n.as_u64().map_or_else(|| n.to_string(), count))).collect();