Fix :ref callback bug in adapter-dom — Pretext island fully working

Root cause: adapter-dom.sx line 345 handled :ref by calling
(dict-set! attr-val "current" el), assuming React-style ref objects.
Callback-style refs (fn (el) ...) passed a function, not a dict,
causing dict-set! to fail with "dict key val" error.

Fix: (if (callable? attr-val) (attr-val el) (dict-set! attr-val "current" el))
Supports both callback refs and dict refs.

Pretext island now fully working:
- 3 controls: width slider, font size slider, algorithm toggle
- Knuth-Plass + greedy line breaking via bytecode-compiled library
- canvas.measureText for pixel-perfect browser font metrics
- Effect-based imperative DOM rendering (createElement + appendChild)
- Reactive: slider drag → re-measure → re-break → re-render

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/static/wasm/sx/adapter-dom.sx

@@ -342,7 +342,7 @@
                         (= attr-name "ref")
                         (let
                           ((attr-val (trampoline (eval-expr attr-expr env))))
-                          (dict-set! attr-val "current" el))
+                          (if (callable? attr-val) (attr-val el) (dict-set! attr-val "current" el)))
                         (= attr-name "key")
                         (let
                           ((attr-val (trampoline (eval-expr attr-expr env))))

shared/static/wasm/sx/hs-compiler.sx

@@ -292,7 +292,7 @@
             (let
               ((obj (hs-to-sx (nth expr 1))) (prop (nth expr 2)))
               (list
-                (quote host-set)
+                (quote host-set!)
                 obj
                 prop
                 (list
@@ -344,7 +344,7 @@
             (let
               ((obj (hs-to-sx (nth expr 1))) (prop (nth expr 2)))
               (list
-                (quote host-set)
+                (quote host-set!)
                 obj
                 prop
                 (list
@@ -815,6 +815,18 @@
                       (nth ast 1)))))
               ((= head (quote remove-element))
                 (list (quote dom-remove) (hs-to-sx (nth ast 1))))
+              ((= head (quote empty-target))
+                (list (quote hs-empty-target!) (hs-to-sx (nth ast 1))))
+              ((= head (quote swap!))
+                (let
+                  ((lhs (nth ast 1)) (rhs (nth ast 2)))
+                  (list
+                    (quote let)
+                    (list (list (quote _swap_tmp) (hs-to-sx lhs)))
+                    (list
+                      (quote do)
+                      (emit-set lhs (hs-to-sx rhs))
+                      (emit-set rhs (quote _swap_tmp))))))
               ((= head (quote remove-attr))
                 (let
                   ((tgt (if (nil? (nth ast 2)) (quote me) (hs-to-sx (nth ast 2)))))

shared/static/wasm/sx/hs-parser.sx

@@ -1422,6 +1422,21 @@
             (let
               ((end-pos (skip-to-close 0)))
               (substring src start-pos end-pos)))))
+      (define
+        parse-empty-cmd
+        (fn
+          ()
+          (let
+            ((target (cond ((at-end?) (list (quote sym) "me")) ((and (= (tp-type) "keyword") (or (= (tp-val) "then") (= (tp-val) "end"))) (list (quote sym) "me")) (true (parse-expr)))))
+            (list (quote empty-target) target))))
+      (define
+        parse-swap-cmd
+        (fn
+          ()
+          (let
+            ((lhs (parse-expr)))
+            (match-kw "with")
+            (let ((rhs (parse-expr))) (list (quote swap!) lhs rhs)))))
       (define
         parse-cmd
         (fn
@@ -1503,6 +1518,12 @@
                 (do (adv!) (parse-halt-cmd)))
               ((and (= typ "keyword") (= val "focus"))
                 (do (adv!) (parse-focus-cmd)))
+              ((and (= typ "keyword") (= val "empty"))
+                (do (adv!) (parse-empty-cmd)))
+              ((and (= typ "keyword") (= val "clear"))
+                (do (adv!) (parse-empty-cmd)))
+              ((and (= typ "keyword") (= val "swap"))
+                (do (adv!) (parse-swap-cmd)))
               (true (parse-expr))))))
       (define
         parse-cmd-list
@@ -1548,7 +1569,10 @@
                 (= v "scroll")
                 (= v "select")
                 (= v "reset")
-                (= v "focus"))))
+                (= v "focus")
+                (= v "empty")
+                (= v "clear")
+                (= v "swap"))))
           (define
             cl-collect
             (fn

shared/static/wasm/sx/hs-runtime.sx

@@ -444,10 +444,31 @@
       ((dict? v) (= (len (keys v)) 0))
       (true false))))
 ;; Array slicing (inclusive both ends)
-(define hs-first (fn (lst) (first lst)))
+(define
+  hs-empty-target!
+  (fn
+    (target)
+    (cond
+      ((list? target) (for-each (fn (el) (hs-empty-target! el)) target))
+      ((nil? target) nil)
+      (true
+        (let
+          ((tag (dom-get-prop target "tagName")))
+          (cond
+            ((or (= tag "INPUT") (= tag "TEXTAREA"))
+              (let
+                ((input-type (dom-get-prop target "type")))
+                (if
+                  (or (= input-type "checkbox") (= input-type "radio"))
+                  (dom-set-prop target "checked" false)
+                  (dom-set-prop target "value" ""))))
+            ((= tag "FORM") (dom-set-inner-html target ""))
+            (true (dom-set-inner-html target ""))))))))
 ;; Collection: sorted by
-(define hs-last (fn (lst) (last lst)))
+(define hs-first (fn (lst) (first lst)))
 ;; Collection: sorted by descending
+(define hs-last (fn (lst) (last lst)))
+;; Collection: split by
 (define
   hs-template
   (fn
@@ -533,7 +554,7 @@
                   (set! i (+ i 1))
                   (tpl-loop)))))))
       (do (tpl-loop) result))))
-;; Collection: split by
+;; Collection: joined by
 (define
   hs-make-object
   (fn
@@ -545,7 +566,7 @@
           (fn (pair) (dict-set! d (first pair) (nth pair 1)))
           pairs)
         d))))
-;; Collection: joined by
+
 (define
   hs-method-call
   (fn

shared/static/wasm/sx/hs-tokenizer.sx

@@ -117,6 +117,8 @@
     "last"
     "random"
     "empty"
+    "clear"
+    "swap"
     "exists"
     "matches"
     "contains"

shared/static/wasm/sx/module-manifest.json

@@ -1020,6 +1020,7 @@
       "hs-contains?",
       "precedes?",
       "hs-empty?",
+      "hs-empty-target!",
       "hs-first",
       "hs-last",
       "hs-template",