solvers, meshers: stop with Cancelled at each loop's natural points

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

crates/mesh/src/hex/mod.rs

@@ -276,6 +276,7 @@ pub fn hex_mesh(surface: &BoundarySurface, faces: &[Option<Surface>], field: &dy
     };
     let mut reasons: Vec<String> = Vec::new();
     for &method in methods {
+        fieldcraft_model::progress::check()?;
         let mut last = None;
         match method {
             HexMethod::Extrude | HexMethod::Revolve => {
@@ -287,6 +288,7 @@ pub fn hex_mesh(surface: &BoundarySurface, faces: &[Option<Surface>], field: &dy
                     }
                 };
                 for setup in setups {
+                    fieldcraft_model::progress::check()?;
                     // The cross-section is laid out once per frame; refinement retries reuse it.
                     let prepared = match layered::prepare(&ctx, setup) {
                         Ok(p) => p,
@@ -364,6 +366,7 @@ fn candidate_setups(ctx: &Ctx, method: HexMethod) -> std::result::Result<Vec<lay
 fn with_refinement(ctx: &Ctx, method: HexMethod, run: impl Fn(u32) -> Result<Raw>) -> Result<HexMesh> {
     let mut last = Error::Failed("no attempt".into());
     for refine in 0..=MAX_REFINE {
+        fieldcraft_model::progress::check()?;
         match run(refine).and_then(|raw| finish(&Cells::one(ctx), raw, method)) {
             Ok(mesh) => return Ok(mesh),
             Err(e @ Error::Failed(_)) => last = e,

crates/mesh/src/octree/mod.rs

@@ -251,6 +251,7 @@ pub fn octree_hex_mesh(surface: &BoundarySurface, field: &dyn SizeField, options
     let mut hints: Vec<P> = Vec::new();
     let mut retries: Vec<String> = Vec::new();
     for attempt in 0..options.attempts {
+        fieldcraft_model::progress::check()?;
         let cap = if attempt == 0 {
             options.max_elements
         } else {

crates/mesh/src/tet/improve.rs

@@ -460,6 +460,7 @@ pub fn improve(cx: &mut TetComplex, ctx: &Context, o: &ImproveOptions) -> Result
         stats.passes += 1;
         fieldcraft_model::progress::stage("Improvement pass", Some(o.max_passes as f64), "");
         fieldcraft_model::progress::count(stats.passes as f64);
+        fieldcraft_model::progress::check()?;
         let before = match carried.take() {
             Some(b) => b,
             None => indicators(cx)?,

crates/mesh/src/tet/mod.rs

@@ -491,6 +491,7 @@ pub fn quality_mesh(surface: &BoundarySurface, cdt: &TetMesh, analytic: Vec<Opti
     progress::stage("Refinement round", Some(o.rounds as f64), "");
     for round in 0..o.rounds {
         progress::count((round + 1) as f64);
+        progress::check()?;
         let stats = refine::refine(&mut cx, &ctx, &ropt)?;
         let quiet = stats.interior + stats.boundary == 0;
         let stopped = stats.stopped.clone();
@@ -514,6 +515,7 @@ pub fn quality_mesh(surface: &BoundarySurface, cdt: &TetMesh, analytic: Vec<Opti
     }
     // Put the boundary vertices on the exact surfaces (the tessellation is within its chordal
     // tolerance of them).
+    progress::check()?;
     progress::stage("Snapping to the geometry", None, "");
     report.unsnapped = snap_to_geometry(&mut cx, &exact, true)?;
     let c = cx.compact()?;

crates/mesh/src/tet/refine.rs

@@ -263,6 +263,10 @@ pub fn refine(cx: &mut TetComplex, ctx: &Context, o: &RefineOptions) -> Result<R
     while head < queue.len() {
         let t = queue.get(head).copied().unwrap_or(NONE);
         head += 1;
+        // A round can insert hundreds of thousands of vertices: stop between them when asked.
+        if head.is_multiple_of(1024) {
+            fieldcraft_model::progress::check()?;
+        }
         // Keep the queue's memory bounded: drop the processed prefix now and then.
         if head > 1 << 20 {
             queue.drain(..head);