'dynClass' pseudo-attribute

2 files changed, 33 insertions, 2 deletions

diff --git a/lib/js/urweb.js b/lib/js/urweb.js
index a3976fef..ba73e744 100644
--- a/lib/js/urweb.js
+++ b/lib/js/urweb.js
@@ -47,7 +47,7 @@ function cons(v, ls) {
 function rev(ls) {
     var acc = null;
     for (; ls; ls = ls.next)
-        acc = cons(ls.data, acc);
+       acc = cons(ls.data, acc);
     return acc;
 }
 function concat(ls1, ls2) {
@@ -562,7 +562,6 @@ function flattenLocal(s) {
 }
 
 
-
 // Dynamic tree management
 
 function populate(node) {
@@ -899,6 +898,37 @@ function tbx(s) {
     return x;
 }
 
+function dynClass(html, s) {
+    var htmlCls = {v : null};
+    html = flatten(htmlCls, html);
+    htmlCls = htmlCls.v;
+
+    var dummy = document.createElement("body");
+    dummy.innerHTML = html;
+    runScripts(dummy);
+    var html = dummy.firstChild;
+    dummy.removeChild(html);
+    addNode(html);
+
+    var x = document.createElement("script");
+    x.dead = false;
+    x.signal = s;
+    x.sources = null;
+    x.closures = htmlCls;
+    
+    x.recreate = function(v) {
+        for (var ls = x.closures; ls != htmlCls; ls = ls.next)
+            freeClosure(ls.data);
+
+        var cls = {v : null};
+        html.className = flatten(cls, v);
+	x.closures = concat(cls.v, htmlCls);
+    };
+
+    addNode(x);
+    populate(x);
+}
+
 function addOnChange(x, f) {
     var old = x.onchange;
     if (old == null)
diff --git a/lib/ur/basis.urs b/lib/ur/basis.urs
index 17e969ef..08585546 100644
--- a/lib/ur/basis.urs
+++ b/lib/ur/basis.urs
@@ -645,6 +645,7 @@ val tag : attrsGiven ::: {Type} -> attrsAbsent ::: {Type}
              [useOuter ~ useInner] =>
              [bindOuter ~ bindInner] =>
            option css_class
+	   -> option (signal css_class)
            -> $attrsGiven
            -> tag (attrsGiven ++ attrsAbsent)
                   ctxOuter ctxInner useOuter bindOuter