web-client: simplify reconcile-children

Message

Use map for the target node list and fold the empty->populated branch into the general moves path: first populate is now the same prune+moves flow with a preceding bulk clear (dropping possible pre-existing static markup), removing the duplicated append loop.

Changed

 src/sigil/web/client.sgl | 64 +++++++++++++++++++++++++++++-----------------------------------
 1 file changed, 29 insertions(+), 35 deletions(-)

Diff

src/sigil/web/client.sglmodified

@@ -465,41 +465,35 @@

465

;; dropped nodes, then insert-before only the nodes whose position

466

;; actually changed. The unchanged common case makes zero DOM calls.

467

(define (web-client-reconcile-children! parent old-records ordered)

−468

(let ((target (let collect ((rest ordered) (acc '()))

−469

(if (null? rest)

−470

(reverse acc)

−471

(collect (cdr rest)

−472

(cons (web-client-record-node (car rest)) acc))))))

−473

(cond

−474

;; populated -> empty: one bulk clear beats N removals.

−475

((null? target)

−476

(when (pair? old-records)

−477

(wasm-dom-replace-children parent)))

−478

;; empty -> populated (first populate of this parent): clear any

−479

;; pre-existing content (e.g. static placeholder markup in a root

−480

;; that was never rendered into) and append in order, exactly like

−481

;; the old path did on initial render.

−482

((null? old-records)

−483

(wasm-dom-replace-children parent)

−484

(for-each

−485

(lambda (node) (wasm-dom-append-child parent node))

−486

target))

−487

(else

−488

;; Drop old top-level nodes not carried into the new set, keeping

−489

;; the still-attached nodes in their current DOM order.

−490

(let ((current (let prune ((rest old-records) (acc '()))

−491

(if (null? rest)

−492

(reverse acc)

−493

(let ((node (web-client-record-node (car rest))))

−494

(if (memv node target)

−495

(prune (cdr rest) (cons node acc))

−496

(begin

−497

(wasm-dom-remove-child parent node)

−498

(prune (cdr rest) acc))))))))

−499

(for-each

−500

(lambda (op)

−501

(wasm-dom-insert-before parent (car op) (cdr op)))

−502

(web-client-child-moves current target)))))))

+468

(let ((target (map web-client-record-node ordered)))

+469

(if (null? target)

+470

;; populated -> empty: one bulk clear beats N removals. (When both

+471

;; sides are empty nothing is touched, so a childless element costs

+472

;; no bridge call per render.)

+473

(when (pair? old-records)

+474

(wasm-dom-replace-children parent))

+475

(begin

+476

;; empty -> populated (first populate of this parent): clear any

+477

;; pre-existing content first (e.g. static placeholder markup in

+478

;; a root that was never rendered into), like the old path did on

+479

;; initial render. The moves below then append every node.

+480

(when (null? old-records)

+481

(wasm-dom-replace-children parent))

+482

;; Drop old top-level nodes not carried into the new set, keeping

+483

;; the still-attached nodes in their current DOM order.

+484

(let ((current (let prune ((rest old-records) (acc '()))

+485

(if (null? rest)

+486

(reverse acc)

+487

(let ((node (web-client-record-node (car rest))))

+488

(if (memv node target)

+489

(prune (cdr rest) (cons node acc))

+490

(begin

+491

(wasm-dom-remove-child parent node)

+492

(prune (cdr rest) acc))))))))

+493

(for-each

+494

(lambda (op)

+495

(wasm-dom-insert-before parent (car op) (cdr op)))

+496

(web-client-child-moves current target)))))))

497

498

(define (web-client-patch-children parent old-records new-values)

499

(let loop ((rest (web-client-normalize-children new-values))