add ability to disabled/enable a fieldset

Author: sspickle

lib/glow/primitives.js

@@ -3047,17 +3047,19 @@
     function fieldset(args) { // a form fieldset
         if (!(this instanceof fieldset)) return new fieldset(args)  // so fieldset() is like new fieldset()
         var cvs = canvas.get_selected()
-        var attrs = {pos:cvs.caption_anchor, legend:'', width:cvs.width}
+        var attrs = {pos:cvs.caption_anchor, legend:'', width:cvs.width, disabled:false}
 
         for (a in attrs) {
             if (args[a] !== undefined) {
                 attrs[a] = args[a]
                 delete args[a]
             }
         }
+        attrs.disabled = booleanize(attrs.disabled)       
 
         let fs_css = {width:`${attrs.width}px`}
-        attrs.jfieldset = $('<fieldset>').css(fs_css).appendTo(attrs.pos)
+        let fs_string =`<fieldset ${attrs.disabled?'disabled':''}>`
+        attrs.jfieldset = $(fs_string).css(fs_css).appendTo(attrs.pos)
         $(`<legend>${attrs.legend}</legend>`).appendTo(attrs.jfieldset)
 
         var cfieldset = { // this structure implements a JavaScript "closure"
@@ -3066,7 +3068,15 @@
                 return attrs.legend
             },
             set legend(value) {
-                throw new Error("Cannot change a fieldsets legend.")
+                attrs.legend = value
+                $(attrs.jfieldset).find('legend').html(value)
+            },
+            get disabled(){
+                return attrs.disabled
+            },
+            set disabled(value) {
+                attrs.disabled = booleanize(value)
+                $(attrs.jfieldset).attr('disabled', attrs.disabled)
             },
             get pos() {
                 return attrs.jfieldset