Merge pull request #73 from praeclarum/prerender

Prerender HTML to help SEO and load time

Ooui.AspNetCore/ElementResult.cs

@@ -1,33 +1,56 @@
 using System;
-using System.Text;
+using System.Text;
-using System.Threading.Tasks;
+using System.Threading.Tasks;
-using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Http;
-
+using Microsoft.AspNetCore.Mvc;
+
 namespace Ooui.AspNetCore
 {
     public class ElementResult : ActionResult
-    {
+    {
         readonly Element element;
-        readonly string title;
+        readonly string title;
-
+
         public ElementResult (Element element, string title = "")
-        {
+        {
             this.element = element;
-            this.title = title;
+            this.title = title;
         }
 
-        public override async Task ExecuteResultAsync (ActionContext context)
+        public override async Task ExecuteResultAsync (ActionContext context)
         {
             var response = context.HttpContext.Response;
             response.StatusCode = 200;
             response.ContentType = "text/html; charset=utf-8";
+
+            if (element.WantsFullScreen) {
+                element.Style.Width = GetCookieDouble (context.HttpContext.Request.Cookies, "oouiWindowWidth", 32, 640, 10000);
+                element.Style.Height = GetCookieDouble (context.HttpContext.Request.Cookies, "oouiWindowHeight", 24, 480, 10000);
+            }
+
             var sessionId = WebSocketHandler.BeginSession (context.HttpContext, element);
-            var html = UI.RenderTemplate (WebSocketHandler.WebSocketPath + "?id=" + sessionId, title: title);
+            var initialHtml = element.OuterHtml;
+            var html = UI.RenderTemplate (WebSocketHandler.WebSocketPath + "?id=" + sessionId, title: title, initialHtml: initialHtml);
             var htmlBytes = Encoding.UTF8.GetBytes (html);
             response.ContentLength = htmlBytes.Length;
             using (var s = response.Body) {
                 await s.WriteAsync (htmlBytes, 0, htmlBytes.Length).ConfigureAwait (false);
             }
         }
+
+        static double GetCookieDouble (IRequestCookieCollection cookies, string key, double min, double def, double max)
+        {
+            if (cookies.TryGetValue (key, out var s)) {
+                if (double.TryParse (s, out var d)) {
+                    if (d < min) return min;
+                    if (d > max) return max;
+                    return d;
+                }
+                return def;
+            }
+            else {
+                return def;
+            }
+        }
     }
 }

Ooui.Forms/Renderers/ViewRenderer.cs

@@ -21,6 +21,8 @@ namespace Ooui.Forms.Renderers
         /// </summary>
         protected virtual bool ManageNativeControlLifetime => true;
 
+		protected override bool HtmlNeedsFullEndElement => TagName == "div";
+
         public ViewRenderer (string tagName = "div")
             : base (tagName)
         {

Ooui.Forms/Renderers/WebViewRenderer.cs

@@ -24,7 +24,7 @@ namespace Ooui.Forms.Renderers
 
                 if (_iframe != null)
                 {
-                    _iframe.Src = html;
+                    _iframe.Source = html;
                 }
             }
             catch (Exception ex)
@@ -47,7 +47,7 @@ namespace Ooui.Forms.Renderers
 
                 if (_iframe != null)
                 {
-                    _iframe.Src = url;
+                    _iframe.Source = url;
                 }
             }
             catch (Exception ex)

Ooui.Forms/VisualElementRenderer.cs

@@ -62,6 +62,8 @@ namespace Ooui.Forms
             }
         }
 
+        protected override bool HtmlNeedsFullEndElement => TagName == "div";
+
         public VisualElementRenderer (string tagName = "div") : base (tagName)
         {
             _propertyChangedHandler = OnElementPropertyChanged;

Ooui/Anchor.cs

@@ -4,10 +4,9 @@ namespace Ooui
 {
     public class Anchor : Element
     {
-        string href = "";
         public string HRef {
-            get => href;
+            get => GetStringAttribute ("href", "");
-            set => SetProperty (ref href, value ?? "", "href");
+            set => SetAttributeProperty ("href", value);
         }
 
         public Anchor ()

Ooui/Button.cs

@@ -9,8 +9,8 @@ namespace Ooui
     {
         ButtonType typ = ButtonType.Submit;
         public ButtonType Type {
-            get => typ;
+            get => GetAttribute ("type", ButtonType.Submit);
-            set => SetProperty (ref typ, value, "type");
+            set => SetAttributeProperty ("type", value);
         }
 
         public Button ()

Ooui/Canvas.cs

@@ -7,16 +7,14 @@ namespace Ooui
         CanvasRenderingContext2D context2d = new CanvasRenderingContext2D ();
         int gotContext2d = 0;
 
-        int width = 300;
         public int Width {
-            get => width;
+            get => GetAttribute ("width", 300);
-            set => SetProperty (ref width, value <= 0 ? 150 : value, "width");
+            set => SetAttributeProperty ("width", value < 0 ? 0 : value);
         }
 
-        int height = 150;
         public int Height {
-            get => height;
+            get => GetAttribute ("height", 150);
-            set => SetProperty (ref height, value <= 0 ? 150 : value, "height");
+            set => SetAttributeProperty ("height", value < 0 ? 0 : value);
         }
 
         public Canvas ()

Ooui/Client.js

@@ -2,6 +2,7 @@
 var debug = false;
 
 const nodes = {};
+const hasText = {};
 
 let socket = null;
 
@@ -35,10 +36,27 @@ function getSize () {
     };
 }
 
+function setCookie (name, value, days) {
+    var expires = "";
+    if (days) {
+        var date = new Date ();
+        date.setTime(date.getTime () + (days*24*60*60*1000));
+        expires = "; expires=" + date.toUTCString();
+    }
+    document.cookie = name + "=" + (value || "")  + expires + "; path=/";
+}
+
+function saveSize (s) {
+    setCookie ("oouiWindowWidth", s.width, 7);
+    setCookie ("oouiWindowHeight", s.height, 7);
+}
+
 // Main entrypoint
 function ooui (rootElementPath) {
 
     var initialSize = getSize ();
+    saveSize (initialSize);
+
     var wsArgs = (rootElementPath.indexOf("?") >= 0 ? "&" : "?") +
         "w=" + initialSize.width + "&h=" + initialSize.height;
 
@@ -123,12 +141,22 @@ function getNode (id) {
     }
 }
 
+function getOrCreateElement (id, tagName) {
+    var e = document.getElementById (id);
+    if (e) {
+        if (e.firstChild && e.firstChild.nodeType == Node.TEXT_NODE)
+            hasText[e.id] = true;
+        return e;
+    }
+    return document.createElement (tagName);
+}
+
 function msgCreate (m) {
     const id = m.id;
     const tagName = m.k;
     const node = tagName === "#text" ?
         document.createTextNode ("") :
-        document.createElement (tagName);
+        getOrCreateElement (id, tagName);
     if (tagName !== "#text")
         node.id = id;
     nodes[id] = node;
@@ -164,6 +192,17 @@ function msgSetAttr (m) {
     if (debug) console.log ("SetAttr", node, m.k, m.v);
 }
 
+function msgRemAttr (m) {
+    const id = m.id;
+    const node = getNode (id);
+    if (!node) {
+        console.error ("Unknown node id", m);
+        return;
+    }
+    node.removeAttribute(m.k);
+    if (debug) console.log ("RemAttr", node, m.k);
+}
+
 function msgCall (m) {
     const id = m.id;
     const node = getNode (id);
@@ -173,6 +212,12 @@ function msgCall (m) {
     }
     const isJQuery = m.k.startsWith ("$.");
     const target = isJQuery ? $(node) : node;
+    if (m.k === "insertBefore" && m.v[0].nodeType == Node.TEXT_NODE && m.v[1] == null && hasText[id]) {
+        // Text is already set so it clear it first
+        if (target.firstChild)
+            target.removeChild (target.firstChild);
+        delete hasText[id];
+    }
     const f = isJQuery ? target[m.k.slice(2)] : target[m.k];
     if (debug) console.log ("Call", node, f, m.v);
     const r = f.apply (target, m.v);
@@ -227,6 +272,9 @@ function processMessage (m) {
         case "setAttr":
             msgSetAttr (m);
             break;
+        case "remAttr":
+            msgRemAttr (m);
+            break;
         case "call":
             msgCall (m);
             break;

Ooui/Div.cs

@@ -5,6 +5,8 @@ namespace Ooui
 {
     public class Div : Element
     {
+        protected override bool HtmlNeedsFullEndElement => true;
+
         public Div ()
             : base ("div")
         {

Ooui/Element.cs

@@ -1,28 +1,29 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 
 namespace Ooui
 {
     public abstract class Element : Node
     {
-        string className = "";
+        readonly Dictionary<string, object> attributes = new Dictionary<string, object> ();
+
         public string ClassName {
-            get => className;
+            get => GetStringAttribute ("class", "");
-            set => SetProperty (ref className, value, "className");
+            set => SetAttributeProperty ("class", value);
         }
 
         public Style Style { get; private set; } = new Style ();
 
-        string title = "";
         public string Title {
-            get => title;
+            get => GetStringAttribute ("title", "");
-            set => SetProperty (ref title, value, "title");
+            set => SetAttributeProperty ("title", value);
         }
 
         bool hidden = false;
         public bool IsHidden {
-            get => hidden;
+            get => GetBooleanAttribute ("hidden");
-            set => SetProperty (ref hidden, value, "hidden");
+            set => SetBooleanAttributeProperty ("hidden", value);
         }
 
         public event TargetEventHandler Click {
@@ -102,8 +103,64 @@ namespace Ooui
             Style.PropertyChanged += HandleStylePropertyChanged;
         }
 
-        public void SetAttribute (string attributeName, string value)
+        protected bool SetAttributeProperty (string attributeName, object newValue, [System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
         {
+            var old = GetAttribute (attributeName);
+            if (old != null && old.Equals (newValue))
+                return false;
+            SetAttribute (attributeName, newValue);
+            OnPropertyChanged (propertyName);
+            return true;
+        }
+
+        protected bool SetBooleanAttributeProperty (string attributeName, bool newValue, [System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
+        {
+            var old = GetAttribute (attributeName) != null;
+            if (old != newValue)
+                return false;
+            if (newValue)
+                SetAttribute (attributeName, string.Empty);
+            else
+                RemoveAttribute (attributeName);
+            OnPropertyChanged (propertyName);
+            return true;
+        }
+
+        protected bool UpdateAttributeProperty (string attributeName, object newValue, string propertyName)
+        {
+            lock (attributes) {
+                if (attributes.TryGetValue (attributeName, out var oldValue)) {
+                    if (newValue != null && newValue.Equals (oldValue))
+                        return false;
+                }
+                attributes[attributeName] = newValue;
+            }
+            OnPropertyChanged (propertyName);
+            return true;
+        }
+
+        protected bool UpdateBooleanAttributeProperty (string attributeName, bool newValue, string propertyName)
+        {
+            lock (attributes) {
+                var oldValue = attributes.ContainsKey (attributeName);
+                if (newValue == oldValue)
+                    return false;
+                if (newValue) {
+                    attributes[attributeName] = "";
+                }
+                else {
+                    attributes.Remove (attributeName);
+                }
+            }
+            OnPropertyChanged (propertyName);
+            return true;
+        }
+
+        public void SetAttribute (string attributeName, object value)
+        {
+            lock (attributes) {
+                attributes[attributeName] = value;
+            }
             Send (new Message {
                 MessageType = MessageType.SetAttribute,
                 TargetId = Id,
@@ -112,6 +169,62 @@ namespace Ooui
             });
         }
 
+        public object GetAttribute (string attributeName)
+        {
+            lock (attributes) {
+                attributes.TryGetValue (attributeName, out var v);
+                return v;
+            }
+        }
+
+        public T GetAttribute<T> (string attributeName, T defaultValue)
+        {
+            lock (attributes) {
+                attributes.TryGetValue (attributeName, out var v);
+                if (v is T) {
+                    return (T)v;
+                }
+                else {
+                    return defaultValue;
+                }
+            }
+        }
+
+        public bool GetBooleanAttribute (string attributeName)
+        {
+            lock (attributes) {
+                return attributes.TryGetValue (attributeName, out var _);
+            }
+        }
+
+        public string GetStringAttribute (string attributeName, string defaultValue)
+        {
+            lock (attributes) {
+                if (attributes.TryGetValue (attributeName, out var v)) {
+                    if (v == null) return "null";
+                    else return v.ToString ();
+                }
+                else {
+                    return defaultValue;
+                }
+            }
+        }
+
+        public void RemoveAttribute (string attributeName)
+        {
+            bool removed;
+            lock (attributes) {
+                removed = attributes.Remove (attributeName);
+            }
+            if (removed) {
+                Send (new Message {
+                    MessageType = MessageType.RemoveAttribute,
+                    TargetId = Id,
+                    Key = attributeName,
+                });
+            }
+        }
+
         void HandleStylePropertyChanged (object sender, PropertyChangedEventArgs e)
         {
             SendSet ("style." + Style.GetJsName (e.PropertyName), Style[e.PropertyName]);
@@ -130,5 +243,38 @@ namespace Ooui
                     return base.SaveStateMessageIfNeeded (message);
             }
         }
+
+        protected virtual bool HtmlNeedsFullEndElement => false;
+
+        public override void WriteOuterHtml (System.Xml.XmlWriter w)
+        {
+            w.WriteStartElement (TagName);
+            w.WriteAttributeString ("id", Id);
+            var style = Style.ToString ();
+            if (style.Length > 0) {
+                w.WriteAttributeString ("style", style);
+            }
+            lock (attributes) {
+                foreach (var a in attributes) {
+                    var value = (a.Value == null) ? "null" : Convert.ToString (a.Value, System.Globalization.CultureInfo.InvariantCulture);
+                    w.WriteAttributeString (a.Key, value);
+                }
+            }
+            WriteInnerHtml (w);
+            if (HtmlNeedsFullEndElement) {
+                w.WriteFullEndElement ();
+            }
+            else {
+                w.WriteEndElement ();
+            }
+        }
+
+        public virtual void WriteInnerHtml (System.Xml.XmlWriter w)
+        {
+            var children = Children;
+            foreach (var c in children) {
+                c.WriteOuterHtml (w);
+            }
+        }
     }
 }

Ooui/EventTarget.cs

@@ -83,12 +83,12 @@ namespace Ooui
             }
         }
 
-        protected bool SetProperty<T> (ref T backingStore, T newValue, string attributeName, [System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
+        protected bool SetProperty<T> (ref T backingStore, T newValue, string jsPropertyName, [System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
         {
             if (EqualityComparer<T>.Default.Equals (backingStore, newValue))
                 return false;
             backingStore = newValue;
-            SendSet (attributeName, newValue);
+            SendSet (jsPropertyName, newValue);
             OnPropertyChanged (propertyName);
             return true;
         }
@@ -120,12 +120,12 @@ namespace Ooui
             Send (Message.Call (Id, methodName, args));
         }
 
-        protected void SendSet (string attributeName, object value)
+        protected void SendSet (string jsPropertyName, object value)
         {
             Send (new Message {
                 MessageType = MessageType.Set,
                 TargetId = Id,
-                Key = attributeName,
+                Key = jsPropertyName,
                 Value = value,
             });
         }
@@ -169,6 +169,11 @@ namespace Ooui
                         state.Add (message);
                     });
                     break;
+                case MessageType.RemoveAttribute:
+                    this.UpdateStateMessages (state => {
+                        state.RemoveAll (x => x.MessageType == MessageType.SetAttribute && x.Key == message.Key);
+                    });
+                    return true;
                 case MessageType.Listen:
                     AddStateMessage (message);
                     break;

Ooui/Form.cs

@@ -6,20 +6,18 @@ namespace Ooui
     {
         string action = "";
         public string Action {
-            get => action;
+            get => GetStringAttribute ("action", "");
-            set => SetProperty (ref action, value ?? "", "action");
+            set => SetAttributeProperty ("action", value ?? "");
         }
 
-		string method = "GET";
 		public string Method {
-			get => method;
+            get => GetStringAttribute ("method", "GET");
-			set => SetProperty (ref method, value ?? "", "method");
+            set => SetAttributeProperty ("method", value ?? "");
 		}
 
-		string enctype = "application/x-www-form-urlencoded";
 		public string EncodingType {
-			get => enctype;
+            get => GetStringAttribute ("enctype", "application/x-www-form-urlencoded");
-			set => SetProperty (ref enctype, value ?? "", "enctype");
+            set => SetAttributeProperty ("enctype", value ?? "");
 		}
 
 		public event TargetEventHandler Submit {

Ooui/FormControl.cs

@@ -4,16 +4,15 @@ namespace Ooui
 {
     public abstract class FormControl : Element
     {
-        string name = "";
         public string Name {
-            get => name;
+            get => GetStringAttribute ("name", "");
-            set => SetProperty (ref name, value, "name");
+            set => SetAttributeProperty ("name", value);
         }
 
         bool isDisabled = false;
         public bool IsDisabled {
-            get => isDisabled;
+            get => GetBooleanAttribute ("disabled");
-            set => SetProperty (ref isDisabled, value, "disabled");
+            set => SetBooleanAttributeProperty ("disabled", value);
         }
 
         public FormControl (string tagName)

Ooui/Iframe.cs

@@ -2,17 +2,15 @@
 {
     public class Iframe : Element
     {
-        public Iframe()
+        public string Source
-                : base("iframe")
         {
-
+            get => GetStringAttribute ("src", null);
+            set => SetAttributeProperty ("src", value);
         }
 
-        string src = null;
+        public Iframe ()
-        public string Src
+            : base ("iframe")
         {
-            get => src;
-            set => SetProperty(ref src, value, "src");
         }
     }
 }

Ooui/Image.cs

@@ -4,10 +4,10 @@ namespace Ooui
 {
     public class Image : Element
     {
-        string src = "";
+        public string Source
-        public string Source {
+        {
-            get => src;
+            get => GetStringAttribute ("src", null);
-            set => SetProperty (ref src, value ?? "", "src");
+            set => SetAttributeProperty ("src", value);
         }
 
         public Image ()

Ooui/Input.cs

@@ -7,16 +7,14 @@ namespace Ooui
 {
     public class Input : FormControl
     {
-        InputType typ = InputType.Text;
         public InputType Type {
-            get => typ;
+            get => GetAttribute ("type", InputType.Text);
-            set => SetProperty (ref typ, value, "type");
+            set => SetAttributeProperty ("type", value);
         }
 
-        string val = "";
         public string Value {
-            get => val;
+            get => GetStringAttribute ("value", "");
-            set => SetProperty (ref val, value ?? "", "value");
+            set => SetAttributeProperty ("value", value ?? "");
         }
 
         public double NumberValue {
@@ -35,37 +33,33 @@ namespace Ooui
             remove => RemoveEventListener ("change", value);
         }
 
-        string placeholder = "";
         public string Placeholder {
-            get => placeholder;
+            get => GetStringAttribute ("placeholder", "");
-            set => SetProperty (ref placeholder, value, "placeholder");
+            set => SetAttributeProperty ("placeholder", value ?? "");
         }
 
-        bool isChecked = false;
         public bool IsChecked {
-            get => isChecked;
+            get => GetBooleanAttribute ("checked");
             set {
-                SetProperty (ref isChecked, value, "checked");
+                if (SetBooleanAttributeProperty ("checked", value)) {
-                TriggerEventFromMessage (Message.Event (Id, "change", isChecked));
+                    TriggerEventFromMessage (Message.Event (Id, "change", IsChecked));
+                }
             }
         }
 
-        double minimum = 0;
         public double Minimum {
-            get => minimum;
+            get => GetAttribute ("min", 0.0);
-            set => SetProperty (ref minimum, value, "min");
+            set => SetAttributeProperty ("min", value);
         }
 
-        double maximum = 100;
         public double Maximum {
-            get => maximum;
+            get => GetAttribute ("max", 100.0);
-            set => SetProperty (ref maximum, value, "max");
+            set => SetAttributeProperty ("max", value);
         }
 
-        double step = 1;
         public double Step {
-            get => step;
+            get => GetAttribute ("step", 1.0);
-            set => SetProperty (ref step, value, "step");
+            set => SetAttributeProperty ("step", value);
         }
 
         public Input ()
@@ -86,10 +80,10 @@ namespace Ooui
             if (message.TargetId == Id && message.MessageType == MessageType.Event && (message.Key == "change" || message.Key == "input")) {
                 // Don't need to notify here because the base implementation will fire the event
                 if (Type == InputType.Checkbox) {
-                    isChecked = message.Value != null ? Convert.ToBoolean (message.Value) : false;
+                    UpdateBooleanAttributeProperty ("checked", message.Value != null ? Convert.ToBoolean (message.Value) : false, "IsChecked");
                 }
                 else {
-                    val = message.Value != null ? Convert.ToString (message.Value) : "";
+                    UpdateAttributeProperty ("value", message.Value != null ? Convert.ToString (message.Value) : "", "Value");
                 }
             }
             return base.TriggerEventFromMessage (message);

Ooui/Label.cs

@@ -4,10 +4,9 @@ namespace Ooui
 {
     public class Label : Element
     {
-        Element htmlFor = null;
         public Element For {
-            get => htmlFor;
+            get => GetAttribute<Element> ("for", null);
-            set => SetProperty (ref htmlFor, value, "htmlFor");
+            set => SetAttributeProperty ("for", value);
         }
 
         public Label ()

Ooui/Message.cs

@@ -48,6 +48,8 @@ namespace Ooui
         Set,
         [EnumMember (Value = "setAttr")]
         SetAttribute,
+        [EnumMember(Value = "remAttr")]
+        RemoveAttribute,
         [EnumMember(Value = "call")]
         Call,
         [EnumMember(Value = "listen")]

Ooui/Node.cs

@@ -180,5 +180,24 @@ namespace Ooui
             }
             return false;
         }
+
+        public virtual string OuterHtml {
+            get {
+                using (var stream = new System.IO.MemoryStream ()) {
+                    var settings = new System.Xml.XmlWriterSettings {
+                        OmitXmlDeclaration = true,
+                        ConformanceLevel = System.Xml.ConformanceLevel.Fragment,
+                        CloseOutput = false,
+                    };
+                    using (var w = System.Xml.XmlWriter.Create (stream, settings)) {
+                        WriteOuterHtml (w);
+                    }
+                    stream.Position = 0;
+                    return new System.IO.StreamReader (stream).ReadToEnd ();
+                }
+            }
+        }
+
+        public abstract void WriteOuterHtml (System.Xml.XmlWriter w);
     }
 }

Ooui/Option.cs

@@ -4,22 +4,19 @@ namespace Ooui
 {
     public class Option : Element
     {
-        string val = "";
         public string Value {
-            get => val;
+            get => GetStringAttribute ("value", "");
-            set => SetProperty (ref val, value ?? "", "value");
+            set => SetAttributeProperty ("value", value ?? "");
         }
 
-        string label = "";
         public string Label {
-            get => label;
+            get => GetStringAttribute ("label", "");
-            set => SetProperty (ref label, value ?? "", "label");
+            set => SetAttributeProperty ("label", value ?? "");
         }
 
-        bool defaultSelected = false;
         public bool DefaultSelected {
-            get => defaultSelected;
+            get => GetBooleanAttribute ("selected");
-            set => SetProperty (ref defaultSelected, value, "defaultSelected");
+            set => SetBooleanAttributeProperty ("selected", value);
         }
 
         public Option ()

Ooui/Select.cs

@@ -4,10 +4,9 @@ namespace Ooui
 {
     public class Select : FormControl
     {
-        string val = "";
         public string Value {
-            get => val;
+            get => GetStringAttribute ("value", "");
-            set => SetProperty (ref val, value ?? "", "value");
+            set => SetAttributeProperty ("value", value ?? "");
         }
 
         public event TargetEventHandler Change {
@@ -35,6 +34,7 @@ namespace Ooui
         protected override void OnChildInsertedBefore (Node newChild, Node referenceChild)
         {
             base.OnChildInsertedBefore (newChild, referenceChild);
+            var val = Value;
             if (string.IsNullOrEmpty (val) && newChild is Option o && !string.IsNullOrEmpty (o.Value)) {
                 val = o.Value;
             }
@@ -43,7 +43,8 @@ namespace Ooui
         protected override bool TriggerEventFromMessage (Message message)
         {
             if (message.TargetId == Id && message.MessageType == MessageType.Event && (message.Key == "change" || message.Key == "input")) {
-                val = message.Value != null ? Convert.ToString (message.Value) : "";
+                SetAttribute ("value", message.Value != null ? Convert.ToString (message.Value) : "");
+                OnPropertyChanged ("Value");
             }
             return base.TriggerEventFromMessage (message);
         }

Ooui/Style.cs

@@ -399,7 +399,7 @@ namespace Ooui
                     o.Append (head);
                     o.Append (p.Key);
                     o.Append (":");
-                    o.Append (String.Format (System.Globalization.CultureInfo.InvariantCulture, "{0}", p.Value));
+                    o.Append (Convert.ToString (p.Value, System.Globalization.CultureInfo.InvariantCulture));
                     head = ";";
                 }
             }

Ooui/TextArea.cs

@@ -20,18 +20,19 @@ namespace Ooui
             set => SetProperty (ref val, value ?? "", "value");
         }
 
-        int rows = 2;
         public int Rows {
-            get => rows;
+            get => GetAttribute ("rows", 2);
-            set => SetProperty (ref rows, value, "rows");
+            set => SetAttributeProperty ("rows", value);
         }
 
         int cols = 20;
         public int Columns {
-            get => cols;
+            get => GetAttribute ("cols", 20);
-            set => SetProperty (ref cols, value, "cols");
+            set => SetAttributeProperty ("cols", value);
         }
 
+        protected override bool HtmlNeedsFullEndElement => true;
+
         public TextArea ()
             : base ("textarea")
         {
@@ -53,5 +54,10 @@ namespace Ooui
             }
             return base.TriggerEventFromMessage (message);
         }
+
+        public override void WriteInnerHtml (System.Xml.XmlWriter w)
+        {
+            w.WriteString (val ?? "");
+        }
     }
 }

Ooui/TextNode.cs

@@ -20,5 +20,10 @@ namespace Ooui
         {
             Text = text;
         }
+
+        public override void WriteOuterHtml (System.Xml.XmlWriter w)
+        {
+            w.WriteString (text);
+        }
     }
 }

Ooui/UI.cs

@@ -44,7 +44,10 @@ namespace Ooui
   <style>@Styles</style>
 </head>
 <body>
-<div id=""ooui-body"" class=""container-fluid""></div>
+
+<div id=""ooui-body"" class=""container-fluid"">
+@InitialHtml
+</div>
 
 <script type=""text/javascript"" src=""https://ajax.aspnetcdn.com/ajax/jquery/jquery-2.2.0.min.js""></script>
 <script type=""text/javascript"" src=""https://gitcdn.github.io/bootstrap-toggle/2.2.2/js/bootstrap-toggle.min.js""></script>
@@ -390,9 +393,9 @@ namespace Ooui
             }
         }
 
-        public static string RenderTemplate (string webSocketPath, string title = "")
+        public static string RenderTemplate (string webSocketPath, string title = "", string initialHtml = "")
         {
-            return Template.Replace ("@WebSocketPath", webSocketPath).Replace ("@Styles", rules.ToString ()).Replace ("@Title", title);
+            return Template.Replace ("@WebSocketPath", webSocketPath).Replace ("@Styles", rules.ToString ()).Replace ("@Title", title).Replace ("@InitialHtml", initialHtml);
         }
 
         class DataHandler : RequestHandler

Tests/CanvasTests.cs

@@ -58,8 +58,8 @@ namespace Tests
             Assert.AreEqual (480, c.Height);
             c.Width = 0;
             c.Height = -100;
-            Assert.AreEqual (150, c.Width);
+            Assert.AreEqual (0, c.Width);
-            Assert.AreEqual (150, c.Height);
+            Assert.AreEqual (0, c.Height);
         }
     }
 }

Tests/WriteHtmlTests.cs

@@ -0,0 +1,95 @@
+using System;
+
+#if NUNIT
+using NUnit.Framework;
+using TestClassAttribute = NUnit.Framework.TestFixtureAttribute;
+using TestMethodAttribute = NUnit.Framework.TestCaseAttribute;
+#else
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+#endif
+
+using Ooui;
+
+namespace Tests
+{
+    [TestClass]
+    public class WriteHtmlTests
+    {
+        System.Text.RegularExpressions.Regex idre = new System.Text.RegularExpressions.Regex ("\\sid=\"[^\"]*\"");
+
+        string OuterHtmlWithoutIds (Element e)
+        {
+            return idre.Replace (e.OuterHtml, "");
+        }
+
+        [TestMethod]
+        public void TextAreaWithTextStyled ()
+        {
+            var e = new TextArea {
+                Value = "Hello World!",
+            };
+            e.Style.BackgroundColor = "#18f";
+            Assert.AreEqual ("<textarea style=\"background-color:#18f\">Hello World!</textarea>", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void TextAreaEmptyStyled ()
+        {
+            var e = new TextArea ();
+            e.Style.BackgroundColor = "#18f";
+            Assert.AreEqual ("<textarea style=\"background-color:#18f\"></textarea>", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void Style ()
+        {
+            var e = new Div ();
+            e.Style.BackgroundColor = "#18f";
+            Assert.AreEqual ("<div style=\"background-color:#18f\"></div>", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void TwoGrandChildren ()
+        {
+            var e = new Div (new Div (new Anchor (), new Anchor ()), new Paragraph ());
+            Assert.AreEqual ("<div><div><a /><a /></div><p /></div>", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void Child ()
+        {
+            var e = new Div (new Anchor ());
+            Assert.AreEqual ("<div><a /></div>", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void TextChild ()
+        {
+            var e = new Paragraph ("Hello world!");
+            Assert.AreEqual ("<p>Hello world!</p>", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void IdIsFirst ()
+        {
+            var e = new Anchor ();
+            Assert.IsTrue (e.OuterHtml.StartsWith ("<a id=\""));
+        }
+
+        [TestMethod]
+        public void EmptyElement ()
+        {
+            var e = new Anchor ();
+            Assert.AreEqual ("<a />", OuterHtmlWithoutIds (e));
+        }
+
+        [TestMethod]
+        public void AnchorHRef ()
+        {
+            var e = new Anchor {
+                HRef = "http://google.com"
+            };
+            Assert.AreEqual ("<a href=\"http://google.com\" />", OuterHtmlWithoutIds (e));
+        }
+    }
+}