Mono

These are some notes on Silverlight Hosting APIs and how the plugin works / should work. They are likely incorrect

Moonlight plugin

How it works

First step: create an <object> element of type application/ag-plugin.

This is not mandatory unless you run silverlight apps written in Microsoft ways:

• The web browser loads HTML, which contains "SilverlightControlHost" element.
• SilverlightControlHost invokes "createSilverlight()" which is defined in the HTML's bound Javascript.
• createSilverlight() invokes createObjectEx() which is defined in silverlight.js.
• createObjectEx() either creates an <object> element of type application/ag-plugin, or download/support links.
• <object> element of type application/ag-plugin is recognized by the moonlight plugin.

We could just directly include such an <object> element in the HTML instead.

Second step: bootstrapping Silverlight control

It is done by moonlight plugin.

• The plugin is triggered by the <object> element.
• It loads the "source" XAML file. If there isn't, then nothing is warned.
• It looks for the implementation class from "x:class", which looks like : "SilverlightProject1.Page;assembly=ClientBin/SilverlightProject1.dll"
  • If there isn't, then Javascript warning is raised.
  • If the referenced type is not an expected type (only Canvas?), then Javascript warning is raised.
• Create a GTK+ canvas for Silverlight object (indicated by "source")

Hosting APIs

System.Silverlight.dll and Microsoft.Scripting.Silverlight.dll are involved.

Microsoft.Scripting.Silverlight is smaller:

• ErrorHandler : static aggregated class of error handling which dispatch managed exceptions to browser.
• HtmlDocumentMemberInjector
• HtmlElementMemberInjector
• IDlrNameScope
• SilverlightPAL
• SilverlightScriptHost
• XamlDlrScriptHost

ScriptableObject

• it is nothing to do with JavaScriptSerializer (methods and events are ignored in the serializer).
• For now simple string and primitive types are supported as method parameters. (See below for details.)

How to enable ScriptableObject in managed code

• Add ScriptableAttribute on the class, and property, method and events.
• Call WebApplication.Current.RegisterScriptableObject(nameOnJS, instance).

How to use ScriptableObject in client Javascript

• registered scriptable objects are accessible via document.getElementById ("SilverlightControl").Content as its properties.
• Properties are created as Javascript objects.
• Events are created as event triggers which expects two arguments (sender, eargs).
• functions are created as functions as they are.
• Types are strictly limited: bool, string, char, numeric types except for Decimal are OK. No other types are allowed (object, Guid, DateTime, IDictionary<string,object>, any custom types). Only In parameters allowed.

Hosted environment

• Every ScriptableObject seems to check its hosting environment. For example, HtmlPage.Document causes an error (NRE at alpha1) outside hosted environment (for example console app).

ScriptableObject injection

See also: http://www.silverlight.net/QuickStarts/Dom/ManagedCodeAccess.aspx

List for some objects/methods that need interaction from managed code to DOM:

• ScriptableObject.GetProperty<T>(string name)
  • T must be derived from ScriptableObject. For example, HtmlPage.Document.GetProperty<object>("documentElement")
• ScriptableObject.SetProperty(string,object)
• HtmlObject.AttachEvent(string name,EventHandler handler)
• HtmlObject.DetachEvent(string name,EventHandler handler)
• generic way to invoke methods (e.g. getElementByTagName(), createElement() etc.)

Error handling

In agclr, System.Windows.ErrorEventHandler and ErrorEventArgs are used to handle errors at managed side.

Microsoft.Scripting.Silverlight.ErrorHandler is (in a sense) the closest API to the browser. It is tied to ErrorEventArgs in agclr and "default_error_handler" in silverlight.js, which

• expects ParserError and RuntimeError as errorType (ParserErrorEventArgs/RuntimeErrorEventArgs in agclr)
• expects errorCode, errorType and errorMessage (ErrorEventArgs properties)

Misc notes

• WebApplication.Current is created and used to serve RegisterScriptableObject().
  • NPN_CreateObject() is likely used.
• I'm not sure if SilverlightScriptHost and SilverlightPAL are created on silverlight apps. ScriptDomainManager.CurrentManager.PAL is not an instance of SilverlightPAL on silverlight apps.
• static property HtmlPage.Document accesses to the document. It somehow causes NRE on non-silverlight app.

Implementation status notes

Already written as DllImport (note that they are not in moon/plugin yet):

• WebApplication
  • InvokeMethodInternal(IntPtr xpp, IntPtr obj, string name,object[] args)
  • GetPropertyInternal(IntPtr xpp,IntPtr obj, string name)
  • SetPropertyInternal(IntPtr xpp,IntPtr obj, string name, object value); They are commonized accessors and used by several classes such as HtmlElement.AppendChild().
• BrowserInformation
  • LoadBrowserInformation(BrowserInformation)
• BrowserRuntimeSettings
  • LoadBrowserRuntimeSettings(BrowserRuntimeSettings)
• HtmlObject
  • AttachEvent(IntPtr xpp, IntPtr obj, string name, EventHandler h)
  • AttachEvent(IntPtr xpp, IntPtr obj, string name, EventHandler<HtmlEventArgs> h)
  • DetachEvent(IntPtr xpp, IntPtr obj, string name, EventHandler h)
  • DetachEvent(IntPtr xpp, IntPtr obj, string name, EventHandler<HtmlEventArgs> h)
• HtmlPage
  • Navigate (IntPtr npp, string uri)
  • Navigate (IntPtr npp, string uri, string target, string features) (returns a handle)
  • NavigateToBookmark (IntPtr xpp, string bookmark)
  • Submit (IntPtr xpp, string formId)

Just rough ideas:

• WebApplication.Current is likely hold a pointer to NPP instance, a pointer to PluginInstance, and so on. Use AppDomain.GetData() to return pointers here.
• WebApplication.RegisterScriptableObject() has to create a NPObject. Also, access to the members must be reflected to the managed object (and vice versa).
• WebApplication.StartupArguments. Not sure what should be set here.
• HtmlTimer. Probably it generates call to setTimeout() and calls Javascript eval(), depending on Enabled and Interval. Not sure where it is used.
• HtmlPage properties:
  • Cookies, string
  • CurrentBookmark, string
  • Document, IntPtr to NPObject?
  • DocumentUri, string
  • QueryString, string or dictionary
  • Window, IntPtr to PluginInstance->window
• HtmlElement.SetStyleAttribute() and RemoveStyleAttribute() ; not sure how it is done.