Stepper: innerHTML batch update replaces per-span DOM manipulation

Replace update-code-highlight's O(n²) for-each loop (79 nth calls +
79 dom-set-attr FFI crossings) with a single innerHTML set via join/map.
Builds the HTML string in WASM, one FFI call to set innerHTML.

858ms → 431ms (WASM) → 101ms (JIT) → 76ms (innerHTML batch)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
2026-03-26 17:12:56 +00:00
parent 226c01bbf6
commit f33eaf8f3a

View File

@@ -1,310 +1,353 @@
(defisland ~home/stepper ()
(let ((source "(div (~cssx/tw :tokens \"text-center\")\n (h1 (~cssx/tw :tokens \"text-3xl font-bold mb-2\")\n (span (~cssx/tw :tokens \"text-rose-500\") \"the \")\n (span (~cssx/tw :tokens \"text-amber-500\") \"joy \")\n (span (~cssx/tw :tokens \"text-emerald-500\") \"of \")\n (span (~cssx/tw :tokens \"text-violet-600 text-4xl\") \"sx\")))")
(steps (signal (list)))
(step-idx (signal 9))
(dom-stack-sig (signal (list)))
(code-tokens (signal (list)))
)
(defisland
~home/stepper
()
(let
((source "(div (~cssx/tw :tokens \"text-center\")\n (h1 (~cssx/tw :tokens \"text-3xl font-bold mb-2\")\n (span (~cssx/tw :tokens \"text-rose-500\") \"the \")\n (span (~cssx/tw :tokens \"text-amber-500\") \"joy \")\n (span (~cssx/tw :tokens \"text-emerald-500\") \"of \")\n (span (~cssx/tw :tokens \"text-violet-600 text-4xl\") \"sx\")))")
(steps (signal (list)))
(step-idx (signal 9))
(dom-stack-sig (signal (list)))
(code-tokens (signal (list))))
(letrec
((split-tag (fn (expr result)
(cond
(not (list? expr))
(append! result {"type" "leaf" "expr" expr})
(empty? expr) nil
(not (= (type-of (first expr)) "symbol"))
(append! result {"type" "leaf" "expr" expr})
(is-html-tag? (symbol-name (first expr)))
(let ((ctag (symbol-name (first expr)))
(cargs (rest expr))
(cch (list))
(cat (list))
(spreads (list))
(ckw false))
(for-each (fn (a)
(cond
(= (type-of a) "keyword") (do (set! ckw true) (append! cat a))
ckw (do (set! ckw false) (append! cat a))
(and (list? a) (not (empty? a))
(= (type-of (first a)) "symbol")
(starts-with? (symbol-name (first a)) "~"))
(do (set! ckw false) (append! spreads a))
:else (do (set! ckw false) (append! cch a))))
cargs)
(append! result {"type" "open" "tag" ctag "attrs" cat "spreads" spreads})
(for-each (fn (c) (split-tag c result)) cch)
(append! result {"type" "close" "tag" ctag "open-attrs" cat "open-spreads" spreads}))
:else
(append! result {"type" "expr" "expr" expr}))))
(build-code-tokens (fn (expr tokens step-ref indent)
(cond
(string? expr)
(do (append! tokens {"text" (str "\"" expr "\"") "cls" "text-emerald-700" "step" (get step-ref "v")})
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(number? expr)
(do (append! tokens {"text" (str expr) "cls" "text-amber-700" "step" (get step-ref "v")})
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(= (type-of expr) "keyword")
(append! tokens {"text" (str ":" (keyword-name expr)) "cls" "text-violet-600" "step" (get step-ref "v")})
(= (type-of expr) "symbol")
(let ((name (symbol-name expr)))
(append! tokens {"text" name "cls"
(cond
(is-html-tag? name) "text-sky-700 font-semibold"
(starts-with? name "~") "text-rose-600 font-semibold"
:else "text-stone-700")
"step" (get step-ref "v")}))
(list? expr)
(when (not (empty? expr))
(let ((head (first expr))
(is-tag (and (= (type-of head) "symbol") (is-html-tag? (symbol-name head))))
(is-comp (and (= (type-of head) "symbol") (starts-with? (symbol-name head) "~")))
(open-step (get step-ref "v")))
(append! tokens {"text" "(" "cls" "text-stone-400" "step" open-step})
(build-code-tokens head tokens step-ref indent)
(when is-tag
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(for-each (fn (a)
(let ((is-child (and (list? a) (not (empty? a))
(= (type-of (first a)) "symbol")
(or (is-html-tag? (symbol-name (first a)))
(starts-with? (symbol-name (first a)) "~"))))
(is-spread (and (list? a) (not (empty? a))
(= (type-of (first a)) "symbol")
(starts-with? (symbol-name (first a)) "~"))))
(if is-spread
;; Component spread: save counter, process, restore
;; All tokens inside share parent open-step
(let ((saved (get step-ref "v"))
(saved-tokens-len (len tokens)))
(append! tokens {"text" " " "cls" "" "step" -1})
(build-code-tokens a tokens step-ref indent)
;; Mark all tokens added during spread as spread tokens
(let mark-loop ((j saved-tokens-len))
(when (< j (len tokens))
(dict-set! (nth tokens j) "spread" true)
(mark-loop (+ j 1))))
(dict-set! step-ref "v" saved))
(if (and is-tag is-child)
(do (append! tokens {"text" (str "\n" (join "" (map (fn (_) " ") (range 0 (+ indent 1))))) "cls" "" "step" -1})
(build-code-tokens a tokens step-ref (+ indent 1)))
(do (append! tokens {"text" " " "cls" "" "step" -1})
(build-code-tokens a tokens step-ref indent))))))
(rest expr))
(append! tokens {"text" ")" "cls" "text-stone-400" "step" open-step})
(when is-tag
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))))
:else nil)))
(steps-to-preview (fn (all-steps target)
;; Recursive descent: build SX expression tree from steps[0..target-1].
;; "open" recurses for children; "close"/end-of-steps returns.
;; Unclosed elements close naturally when steps run out.
(if (or (empty? all-steps) (<= target 0))
nil
(let ((pos (dict "i" 0))
(max-i (min target (len all-steps))))
(letrec
((bc-loop (fn (children)
(if (>= (get pos "i") max-i)
children
(let ((step (nth all-steps (get pos "i")))
(stype (get step "type")))
(cond
(= stype "open")
(do
(dict-set! pos "i" (+ (get pos "i") 1))
(let ((tag (get step "tag"))
(attrs (or (get step "attrs") (list)))
(spreads (or (get step "spreads") (list)))
(inner (bc-loop (list))))
(append! children
(concat (list (make-symbol tag)) spreads attrs inner)))
(bc-loop children))
(= stype "close")
(do (dict-set! pos "i" (+ (get pos "i") 1))
children)
(= stype "leaf")
(do (dict-set! pos "i" (+ (get pos "i") 1))
(append! children (get step "expr"))
(bc-loop children))
(= stype "expr")
(do (dict-set! pos "i" (+ (get pos "i") 1))
(append! children (get step "expr"))
(bc-loop children))
:else
(do (dict-set! pos "i" (+ (get pos "i") 1))
(bc-loop children))))))))
(let ((root (bc-loop (list))))
(cond
(= (len root) 1) (first root)
(empty? root) nil
:else (concat (list (make-symbol "<>")) root))))))))
(get-preview (fn () (dom-query "[data-sx-lake=\"home-preview\"]")))
(get-code-view (fn () (dom-query "[data-code-view]")))
(get-stack (fn () (deref dom-stack-sig)))
(set-stack (fn (v) (reset! dom-stack-sig v)))
(push-stack (fn (el) (reset! dom-stack-sig (append (deref dom-stack-sig) (list el)))))
(pop-stack (fn ()
(let ((s (deref dom-stack-sig)))
(when (> (len s) 1)
(reset! dom-stack-sig (slice s 0 (- (len s) 1)))))))
;; build-code-dom and update-code-highlight removed —
;; the code view is now reactive DOM bound to step-idx signal.
;; No imperative DOM manipulation needed.
(build-code-dom (fn () nil))
(update-code-highlight (fn ()
(let ((code-el (get-code-view))
(cur (deref step-idx))
(tokens (deref code-tokens)))
(when (and code-el (not (empty? tokens)))
(let ((spans (dom-query-all code-el "span")))
(for-each (fn (i)
(when (< i (len tokens))
(let ((sp (nth spans i))
(tok (nth tokens i))
(step-num (get tok "step"))
(base (get tok "cls"))
(is-spread (get tok "spread")))
(when (not (= step-num -1))
(dom-set-attr sp "class"
(str base
(cond
(= step-num cur) " bg-amber-100 rounded px-0.5 font-bold text-sm"
(< step-num cur) " font-bold text-xs"
:else " opacity-40")))))))
(range 0 (min (len spans) (len tokens)))))))))
(do-step (fn ()
(build-code-dom)
(when (< (deref step-idx) (len (deref steps)))
(when (empty? (get-stack))
(let ((p (get-preview)))
(when p (set-stack (list p)))))
(let ((step (nth (deref steps) (deref step-idx)))
(step-type (get step "type"))
(parent (if (empty? (get-stack)) (get-preview) (last (get-stack)))))
(cond
(= step-type "open")
(let ((el (dom-create-element (get step "tag") nil))
(attrs (get step "attrs"))
(spreads (or (get step "spreads") (list))))
(let loop ((i 0))
(when (< i (len attrs))
(dom-set-attr el (keyword-name (nth attrs i)) (nth attrs (+ i 1)))
(loop (+ i 2))))
;; Evaluate spreads via ~cssx/tw (in scope from island env)
(for-each (fn (sp)
(when (and (list? sp) (>= (len sp) 3)
(= (type-of (nth sp 1)) "keyword")
(= (keyword-name (nth sp 1)) "tokens")
(string? (nth sp 2)))
(let ((result (trampoline (~cssx/tw :tokens (nth sp 2)))))
(when (spread? result)
(let ((sattrs (spread-attrs result)))
(for-each (fn (k)
(if (= k "class")
(dom-set-attr el "class"
(str (or (dom-get-attr el "class") "") " " (get sattrs k)))
(dom-set-attr el k (get sattrs k))))
(keys sattrs)))))))
spreads)
(when parent (dom-append parent el))
(push-stack el))
(= step-type "close")
(pop-stack)
(= step-type "leaf")
(when parent
(let ((val (get step "expr")))
(dom-append parent (create-text-node (if (string? val) val (str val))))))
(= step-type "expr")
;; Component expressions handled by lake's reactive render
nil))
(swap! step-idx inc)
(update-code-highlight))))
(rebuild-preview (fn (target)
;; Rebuild preview in one shot from steps-to-preview (pure SX→DOM)
(let ((container (get-preview)))
(when container
(dom-set-prop container "innerHTML" "")
(let ((expr (steps-to-preview (deref steps) target)))
(when expr
(let ((dom (render-to-dom expr (get-render-env nil) nil)))
(when dom
(dom-append container dom)))))
(set-stack (list container))))))
(do-back (fn ()
(when (> (deref step-idx) 0)
(let ((target (- (deref step-idx) 1)))
(rebuild-preview target)
(reset! step-idx target)
(update-code-highlight)
(set-cookie "sx-home-stepper" (freeze-to-sx "home-stepper")))))))
;; Freeze scope for persistence — same mechanism, cookie storage
(freeze-scope "home-stepper" (fn ()
(freeze-signal "step" step-idx)))
;; Restore from cookie on mount (server reads cookie too for SSR)
(let ((saved (get-cookie "sx-home-stepper")))
(when saved
((split-tag (fn (expr result) (cond (not (list? expr)) (append! result {:expr expr :type "leaf"}) (empty? expr) nil (not (= (type-of (first expr)) "symbol")) (append! result {:expr expr :type "leaf"}) (is-html-tag? (symbol-name (first expr))) (let ((ctag (symbol-name (first expr))) (cargs (rest expr)) (cch (list)) (cat (list)) (spreads (list)) (ckw false)) (for-each (fn (a) (cond (= (type-of a) "keyword") (do (set! ckw true) (append! cat a)) ckw (do (set! ckw false) (append! cat a)) (and (list? a) (not (empty? a)) (= (type-of (first a)) "symbol") (starts-with? (symbol-name (first a)) "~")) (do (set! ckw false) (append! spreads a)) :else (do (set! ckw false) (append! cch a)))) cargs) (append! result {:spreads spreads :tag ctag :type "open" :attrs cat}) (for-each (fn (c) (split-tag c result)) cch) (append! result {:open-attrs cat :open-spreads spreads :tag ctag :type "close"})) :else (append! result {:expr expr :type "expr"}))))
(build-code-tokens
(fn
(expr tokens step-ref indent)
(cond
(string? expr)
(do
(append! tokens {:cls "text-emerald-700" :step (get step-ref "v") :text (str "\"" expr "\"")})
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(number? expr)
(do
(append! tokens {:cls "text-amber-700" :step (get step-ref "v") :text (str expr)})
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(= (type-of expr) "keyword")
(append! tokens {:cls "text-violet-600" :step (get step-ref "v") :text (str ":" (keyword-name expr))})
(= (type-of expr) "symbol")
(let ((name (symbol-name expr))) (append! tokens {:cls (cond (is-html-tag? name) "text-sky-700 font-semibold" (starts-with? name "~") "text-rose-600 font-semibold" :else "text-stone-700") :step (get step-ref "v") :text name}))
(list? expr)
(when
(not (empty? expr))
(let
((head (first expr))
(is-tag
(and
(= (type-of head) "symbol")
(is-html-tag? (symbol-name head))))
(is-comp
(and
(= (type-of head) "symbol")
(starts-with? (symbol-name head) "~")))
(open-step (get step-ref "v")))
(append! tokens {:cls "text-stone-400" :step open-step :text "("})
(build-code-tokens head tokens step-ref indent)
(when
is-tag
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))
(for-each
(fn
(a)
(let
((is-child (and (list? a) (not (empty? a)) (= (type-of (first a)) "symbol") (or (is-html-tag? (symbol-name (first a))) (starts-with? (symbol-name (first a)) "~"))))
(is-spread
(and
(list? a)
(not (empty? a))
(= (type-of (first a)) "symbol")
(starts-with? (symbol-name (first a)) "~"))))
(if
is-spread
(let
((saved (get step-ref "v"))
(saved-tokens-len (len tokens)))
(append! tokens {:cls "" :step -1 :text " "})
(build-code-tokens a tokens step-ref indent)
(let
mark-loop
((j saved-tokens-len))
(when
(< j (len tokens))
(dict-set! (nth tokens j) "spread" true)
(mark-loop (+ j 1))))
(dict-set! step-ref "v" saved))
(if
(and is-tag is-child)
(do
(append! tokens {:cls "" :step -1 :text (str "\n" (join "" (map (fn (_) " ") (range 0 (+ indent 1)))))})
(build-code-tokens
a
tokens
step-ref
(+ indent 1)))
(do
(append! tokens {:cls "" :step -1 :text " "})
(build-code-tokens a tokens step-ref indent))))))
(rest expr))
(append! tokens {:cls "text-stone-400" :step open-step :text ")"})
(when
is-tag
(dict-set! step-ref "v" (+ (get step-ref "v") 1)))))
:else nil)))
(steps-to-preview
(fn
(all-steps target)
(if
(or (empty? all-steps) (<= target 0))
nil
(let
((pos (dict "i" 0)) (max-i (min target (len all-steps))))
(letrec
((bc-loop (fn (children) (if (>= (get pos "i") max-i) children (let ((step (nth all-steps (get pos "i"))) (stype (get step "type"))) (cond (= stype "open") (do (dict-set! pos "i" (+ (get pos "i") 1)) (let ((tag (get step "tag")) (attrs (or (get step "attrs") (list))) (spreads (or (get step "spreads") (list))) (inner (bc-loop (list)))) (append! children (concat (list (make-symbol tag)) spreads attrs inner))) (bc-loop children)) (= stype "close") (do (dict-set! pos "i" (+ (get pos "i") 1)) children) (= stype "leaf") (do (dict-set! pos "i" (+ (get pos "i") 1)) (append! children (get step "expr")) (bc-loop children)) (= stype "expr") (do (dict-set! pos "i" (+ (get pos "i") 1)) (append! children (get step "expr")) (bc-loop children)) :else (do (dict-set! pos "i" (+ (get pos "i") 1)) (bc-loop children))))))))
(let
((root (bc-loop (list))))
(cond
(= (len root) 1)
(first root)
(empty? root)
nil
:else (concat (list (make-symbol "<>")) root))))))))
(get-preview (fn () (dom-query "[data-sx-lake=\"home-preview\"]")))
(get-code-view (fn () (dom-query "[data-code-view]")))
(get-stack (fn () (deref dom-stack-sig)))
(set-stack (fn (v) (reset! dom-stack-sig v)))
(push-stack
(fn
(el)
(reset! dom-stack-sig (append (deref dom-stack-sig) (list el)))))
(pop-stack
(fn
()
(let
((s (deref dom-stack-sig)))
(when
(> (len s) 1)
(reset! dom-stack-sig (slice s 0 (- (len s) 1)))))))
(build-code-dom (fn () nil))
(update-code-highlight
(fn
()
(let
((code-el (get-code-view))
(cur (deref step-idx))
(tokens (deref code-tokens)))
(when
(and code-el (not (empty? tokens)))
(dom-set-prop
code-el
"innerHTML"
(join
""
(map
(fn
(tok)
(let
((step-num (get tok "step"))
(base (get tok "cls"))
(text (replace (get tok "text") "&" "&amp;")))
(str
"<span class=\""
base
(cond
(= step-num -1)
""
(= step-num cur)
" bg-amber-100 rounded px-0.5 font-bold text-sm"
(< step-num cur)
" font-bold text-xs"
:else " opacity-40")
"\">"
text
"</span>")))
tokens)))))))
(do-step
(fn
()
(build-code-dom)
(when
(< (deref step-idx) (len (deref steps)))
(when
(empty? (get-stack))
(let ((p (get-preview))) (when p (set-stack (list p)))))
(let
((step (nth (deref steps) (deref step-idx)))
(step-type (get step "type"))
(parent
(if
(empty? (get-stack))
(get-preview)
(last (get-stack)))))
(cond
(= step-type "open")
(let
((el (dom-create-element (get step "tag") nil))
(attrs (get step "attrs"))
(spreads (or (get step "spreads") (list))))
(let
loop
((i 0))
(when
(< i (len attrs))
(dom-set-attr
el
(keyword-name (nth attrs i))
(nth attrs (+ i 1)))
(loop (+ i 2))))
(for-each
(fn
(sp)
(when
(and
(list? sp)
(>= (len sp) 3)
(= (type-of (nth sp 1)) "keyword")
(= (keyword-name (nth sp 1)) "tokens")
(string? (nth sp 2)))
(let
((result (trampoline (~cssx/tw :tokens (nth sp 2)))))
(when
(spread? result)
(let
((sattrs (spread-attrs result)))
(for-each
(fn
(k)
(if
(= k "class")
(dom-set-attr
el
"class"
(str
(or (dom-get-attr el "class") "")
" "
(get sattrs k)))
(dom-set-attr el k (get sattrs k))))
(keys sattrs)))))))
spreads)
(when parent (dom-append parent el))
(push-stack el))
(= step-type "close")
(pop-stack)
(= step-type "leaf")
(when
parent
(let
((val (get step "expr")))
(dom-append
parent
(create-text-node (if (string? val) val (str val))))))
(= step-type "expr")
nil))
(swap! step-idx inc)
(update-code-highlight))))
(rebuild-preview
(fn
(target)
(let
((container (get-preview)))
(when
container
(dom-set-prop container "innerHTML" "")
(let
((expr (steps-to-preview (deref steps) target)))
(when
expr
(let
((dom (render-to-dom expr (get-render-env nil) nil)))
(when dom (dom-append container dom)))))
(set-stack (list container))))))
(do-back
(fn
()
(when
(> (deref step-idx) 0)
(let
((target (- (deref step-idx) 1)))
(rebuild-preview target)
(reset! step-idx target)
(update-code-highlight)
(set-cookie "sx-home-stepper" (freeze-to-sx "home-stepper")))))))
(freeze-scope "home-stepper" (fn () (freeze-signal "step" step-idx)))
(let
((saved (get-cookie "sx-home-stepper")))
(when
saved
(thaw-from-sx saved)
(when (or (< (deref step-idx) 0) (> (deref step-idx) 16))
(when
(or (< (deref step-idx) 0) (> (deref step-idx) 16))
(reset! step-idx 9))))
;; Parse source eagerly (pure computation — works in SSR and client)
(let ((parsed (sx-parse source)))
(when (not (empty? parsed))
(let ((result (list))
(step-ref (dict "v" 0)))
(let
((parsed (sx-parse source)))
(when
(not (empty? parsed))
(let
((result (list)) (step-ref (dict "v" 0)))
(split-tag (first parsed) result)
(reset! steps result)
(let ((tokens (list)))
(let
((tokens (list)))
(dict-set! step-ref "v" 0)
(build-code-tokens (first parsed) tokens step-ref 0)
(reset! code-tokens tokens)))))
;; DOM build via effect (client-only — needs live DOM)
(let ((_eff (effect (fn ()
(schedule-idle (fn ()
(build-code-dom)
(rebuild-preview (deref step-idx))
(update-code-highlight)
(run-post-render-hooks)))))))
(div :class "space-y-4"
;; Code view lake — SSR renders tokenized code with highlighting
(div :data-code-view true
(~cssx/tw :tokens "font-mono bg-stone-50 rounded p-2 overflow-x-auto leading-relaxed whitespace-pre-wrap")
:style "font-size:0.5rem"
(map (fn (tok)
(let ((step (get tok "step"))
(let
((_eff (effect (fn () (schedule-idle (fn () (build-code-dom) (rebuild-preview (deref step-idx)) (update-code-highlight) (run-post-render-hooks)))))))
(div
:class "space-y-4"
(div
:data-code-view true
(~cssx/tw
:tokens "font-mono bg-stone-50 rounded p-2 overflow-x-auto leading-relaxed whitespace-pre-wrap")
:style "font-size:0.5rem"
(map
(fn
(tok)
(let
((step (get tok "step"))
(cur (deref step-idx))
(is-spread (get tok "spread"))
(cls (str (get tok "cls")
(cond
(= step -1) ""
(= step cur) " bg-amber-100 rounded px-0.5 font-bold text-sm"
(< step cur) " font-bold text-xs"
:else " opacity-40"))))
(span :class cls (get tok "text"))))
(cls
(str
(get tok "cls")
(cond
(= step -1)
""
(= step cur)
" bg-amber-100 rounded px-0.5 font-bold text-sm"
(< step cur)
" font-bold text-xs"
:else " opacity-40"))))
(span :class cls (get tok "text"))))
(deref code-tokens)))
;; Controls
(div :class "flex items-center justify-center gap-2 md:gap-3"
(button :on-click (fn (e)
(do-back)
(set-cookie "sx-home-stepper" (freeze-to-sx "home-stepper")))
:class (str "px-2 py-1 rounded text-3xl "
(if (> (deref step-idx) 0)
"text-stone-600 hover:text-stone-800 hover:bg-stone-100"
"text-stone-300 cursor-not-allowed"))
"\u25c0")
(span :class "text-sm text-stone-500 font-mono tabular-nums"
(deref step-idx) " / " (len (deref steps)))
(button :on-click (fn (e)
(do-step)
(set-cookie "sx-home-stepper" (freeze-to-sx "home-stepper")))
:class (str "px-2 py-1 rounded text-3xl "
(if (< (deref step-idx) (len (deref steps)))
"text-violet-600 hover:text-violet-800 hover:bg-violet-50"
"text-violet-300 cursor-not-allowed"))
"\u25b6"))
;; Live preview — shows partial result up to current step.
;; Same SX rendered by server (HTML) and client (DOM).
(lake :id "home-preview"
(steps-to-preview (deref steps) (deref step-idx))))))))
(div
:class "flex items-center justify-center gap-2 md:gap-3"
(button
:on-click (fn
(e)
(do-back)
(set-cookie "sx-home-stepper" (freeze-to-sx "home-stepper")))
:class (str
"px-2 py-1 rounded text-3xl "
(if
(> (deref step-idx) 0)
"text-stone-600 hover:text-stone-800 hover:bg-stone-100"
"text-stone-300 cursor-not-allowed"))
"◀")
(span
:class "text-sm text-stone-500 font-mono tabular-nums"
(deref step-idx)
" / "
(len (deref steps)))
(button
:on-click (fn
(e)
(do-step)
(set-cookie "sx-home-stepper" (freeze-to-sx "home-stepper")))
:class (str
"px-2 py-1 rounded text-3xl "
(if
(< (deref step-idx) (len (deref steps)))
"text-violet-600 hover:text-violet-800 hover:bg-violet-50"
"text-violet-300 cursor-not-allowed"))
"▶"))
(lake
:id "home-preview"
(steps-to-preview (deref steps) (deref step-idx))))))))