I am working on an application at the moment that plays back video with a DirectShow filter. The application is written in WPF and is using MediaElements to play the video. As long as the DirectShow filter is registered the video will play. At the moment I just use regsvr32 to register the filter before playback.
What I was wondering is if it is possible to load the filter from an embedded resource when the application is run? I am trying to avoid needing administrator privileges to register the filter.
Edit:
Ok I'm trying to use this information and come up with a solution. You will have to excuse my lack of knowledge in the DirectShow area. I did not write the filter, I am just trying to come up with a solution using it. I am trying to do a little more research so I understand DirectShow and its components a little better.
I found a handy ComHelper class that I'm using to load the filter.
https://gist.github.com/jjeffery/1568627
I am using the code below to create an instance of the filter.
LibraryModule module = LibraryModule.LoadModule(#"filter.ax");
var comObject = ComHelper.CreateInstance(module, new Guid("c91aa7be-f627-46e3-b79f-2de55da46a8b"));
Is this correct? I'm trying to figure out where to go next. How would I use this to build the filter graph?
Building a filter graph using unregistered filters is possible, but you have to be aware of obstacles and then decide whether it is acceptable or not.
DirectShow filters are COM objects with relaxed requirements for threading. That is, adding filters to graphs does not require full COM registration. Graph's IGraphBuilder::AddFilter will accept an interface pointer of your filter without asking you how you obtained it. This means in particular that if you take care of filter instantiation and then you build the graph manually adding filter and connecting pins - this will definitely work out well.
Filters, that you don't want to be registered, can be otherwise instantiated by creating C++ object directly, or by loading DLL and using its DllGetClassObject exported function the way COM would do it with instantiation through registration.
Another note is that COM class can be registered "per-user" without need to have administrator privileges, and such registration enables standard CoCreateInstance instantiation (but not Intelligent Connect - see below).
The typical problem on the way is scenario when you expect a filter of your interest, such as video/audio decoder, to be added automatically via DirectShow Intelligent Connect. This only works with full COM registration, or the alternate option is API hooking which I omit here. To cut long story short: if you are not registering the filters, you have to instantiate and add them to the filter graph yourself, via code.
A final note on embedding. The filter will still be hosted by DLL, so you will have to load executable code into memory. This means that you cannot load it "from resource" directly. Although there are certain methods to build executable DLL image right in memory, the easiest would be to keep filter DLL with you and load it as regular DLL from external file using LoadLibrary. If you prefer to have single binary, you can embed the DLL as binary resource, then extract into temporary file on runtime and then continue with LoadLibrary from there.
See also:
How can I directly embed a DirectShow Push Source filter in an EXE?
C# Register Embedded Directshow Filter
Can I make my private DirectShow filter discoverable by Moniker by external programs?
Related
My goal is to use Alexa Voice Service(AVS) to control TV,AC.. etc. through an IR blaster.
I have my own IoT application which can be used to on-board the said IR blaster and control it manually. The application supports other devices as well. In a previous implementation I have linked AVS with the application and it is now able to control switches,sockets and bulbs through voice.
When implementing for the blaster what I found was that this could be done by using the device category as "OTHER"(as there aren't a category for blasters) and using Alexa.ModeController Interface? I have to create separate modes for each action of the remote(for AC it would be cool mode, fan mode.. etc.) and include each possible parameter values(1,2,3,4) under that action? Problem with this approach is that the implementation is complex and also device specific i.e. I have to do separate implementations for TV and AC.
Is there a better way to achieve this?
Can you list exactly what actions you want?
ModeController is a primitive one, so it allows defining basically anything, but yes, instance ids must match. Other primitives are the Range Controller and the Toggle Controller. All of them use instance ids for the cases if you have multiple capabilities on the same controller.
There a lot of specific controllers. For example to control AC, you can use the Alexa.ThermostatController
I am developing a commercial VB.net WPF application that needs user generated scripts for controlling the application to be shared between users. The best way that I have come across of accomplishing this so far without writing my own parser is using the Microsoft Script Control.
It would appear that both VBScripts and JScripts run through this control have access to wscript and as a result are too powerful to be shared between programmers and non-technical users for obvious security reasons.
I have considered trying to filter out dangerous scripts with some kind of regex parsing or something but that just seems far too risky and easy to circumvent.
So, is there some way of using this control but blocking its access to the system so that it could be used for controlling only the objects that I give it? If not, could someone recommend a better way of doing this?
I do not particularly mind what language the script would be in at this stage, although having multiple options would be nice.
EDIT: I am basing my conclusion that the control is too powerful for this on the fact that the following JScript code successfully launches notepad when called using the .AddCode and .Run methods of the control.
function test(){
var shell = new ActiveXObject("WScript.shell");
shell.run("notepad.exe", 1);
}
Thanks for all the help,
Sam.
If you just need to kill the ActiveXObject feature which is the entry point to the system, you can silently append some lines to the code you give to the Script Control, like this for example:
ActiveXObject = null; // add this silently
function test(){
var shell = new ActiveXObject("WScript.shell"); // this will now fail
shell.run("notepad.exe", 1);
}
Of course, if you still need to give some functions to your users, you will then need to propose some sort of an API, use the AddObject function (see How To Use the AddObject Method of the Script Control), and the user would use it like this:
ActiveXObject = null; // add this silently
function test(){
// this is a controlled method, because I have added a MyAPI named object
// using AddObject, and this object has a OpenNotepad method.
MyAPI.OpenNotepad();
}
PS: WScript is a, ActiveX Scripting host, so it's not accessible from the Script Control.
PS2: This hack does not work in every Script Control underlying languages. It works in JavaScript, but not in VBScript for example.
From your question, it doesn't look like you gave any consideration to any of the open-source script engines out there. I would suggest that those open-source libraries could solve your sandbox problem much more easily than the Microsoft Script Control.
The way I understand it, your requirements are:
Must be able to pass objects from your program into the scripting environment, so the script can use those objects to interact with the host app.
Must not be allowed to do unsafe things like access files, launch applications, create COM objects, etc.
Given those requirements, you have quite a few options.
The first thing that comes to mind is Jint, an open-source JavaScript interpreter written in .NET that you can embed in your app. You can pass .NET objects to the script. By default, the script can actually access any class in the .NET Framework, but the script is sandboxed by default (using .NET's built-in Code Access Security), so the script can't do anything unsafe. (For example, it could use things like StringBuilder or Regex, but it would get an exception if it tried to use FileStream.) If you want, you can disable the .NET access entirely, but even with it enabled, the default sandbox would probably suit your needs.
If for some reason Jint doesn't meet your requirements, some of the other open-source JavaScript-for-.NET engines I can think of off the top of my head are Jurassic, IronJS, and JavaScript .NET.
If it matters to you, Jint, Jurassic, and IronJS are all available through NuGet.
Can anyone give a high level description of what is going on in the Composite C1 core? In particular I am interested in knowing how the plugin architecture works and what the core components are of the system i.e. when a request arrives what is happening in the architecture. The description doesn't have to be too verbose just a list of steps and the classes involved.
Hopefully one of the core development team would enlighten me... and maybe publish some more API (hint hint more class documentation please).
From request to rendered page
The concrete path a request takes depends on the version of C1 you're using, since it was changed to use Routing in version 2.1.2. So lets see
< 2.1.2
Composite.Core.WebClient.Renderings.RequestInterceptorHttpModule will intercept all incoming requests and figure out if the requested path correspond to a valid C1 page. If it does, the url will be rewritten to the C1 page handler ~/Rendererings/Page.aspx
2.1.1
Composite.Core.Routing.Routes.Register() adds a C1 page route (Composite.Core.Routing.Pages.C1PageRoute) to the Routes-collection that looks at the incoming path, figures out if its a valid C1 page. If it is, it returns an instance of ~/Rendererings/Page.aspx ready to be executed.
Okay, so now we have an instance of a IHttpHandler ready to make up the page to be returned to the client. The actual code for the IHttpHandler is easy to see since its located in ~/Renderers/Page.aspx.cs.
OnPreInit
Here we're figuring out which Page Id and which language that was requested and looking at whether we're in preview mode or not, which datascope etc.
OnInit
Now we're fetching the content from each Content Placeholder of our page, and excuting its functions it may contain. Its done by calling Composite.Core.WebClient.Renderings.Page.PageRenderer.Render passing the current page and our placeholders. Internally it will call the method ExecuteFunctions which will run through the content and recursively resolve C1 function elements (<f:function />), execute them and replace the element with the functions output. This will be done until there are no more function elements in the content in case functions them selves output other functions.
Now the whole content is wrapped in a Asp.Net WebForms control, and inserted into our WebForms page. Since C1 functions can return WebForms controls like UserControl etc., this is necessary for them to work correctly and trigger the Event Lifecycle of WebForms.
And, that's basically it. Rendering of a requested page is very simple and very extendable. For instance is there an extension that enables the usage of MasterPages which simply hooks into this rendering flow very elegantly. And because we're using Routing to map which handler to use, its also possible to forget about ~/Rendering/Page.aspx and just return a MvcHandler if your a Mvc fanatic.
API
Now, when it comes to the more core API's there are many, depending on what you want to do. But you can be pretty sure, no matter what there is the necessary ones to get the job done.
At the deep end we have the Data Layer which most other API's and facades are centered around. This means you can do most things working with the raw data, instead of going through facades all the time. This is possible since most configuration of C1 is done by using its own data layer to store configuration.
The Composite C1 core group have yet to validate/refactor and document all the API's in the system and hence operate with the concept of 'a public API' and what can become an API when the demand is there. The latter is a pretty darn stable API, but without guarantees.
The public API documentation is online at http://api.composite.net/
Functions
Functions is a fundamental part of C1 and is a technique to abstract logic from execution. Basically everything that either performs a action or returns some data/string/values can be candidates for functions. At the lowest level a function is a .Net class implementing the IFunction interface, but luckily there are many easier ways to work with it. Out of the box C1 supports functions defined as XSLT templates, C# methods or Sql. There are also community support for writing functions using Razor or having ASP.Net UserControls (.ascx files) to be functions.
Since all functions are registered in C1 during system startup, we use the Composite.Functions.FunctionFacade to execute whatever function we know the name of. Use the GetFunction to get a reference to a function, and then Execute to execute it and get a return value. Functions can take parameters which are passed as real .Net objects when executing a function. There is also full support for calling functions with Xml markup using the <f:function /> element, meaning that editors, designers, template makers etc. easily can access a wealth of functionality without having to know how to write .Net code.
Read more about functions here http://users.composite.net/C1/Functions.aspx and how to use ie Razor to make functions here http://docs.composite.net/C1/ASP-NET/Razor-Functions.aspx
Globalization and Localization
C1 has full multi-language support in the core. Composite.Core.Localization.LocalizationFacade is used for managing the installed locales in the system; querying, adding and removing. Locales can be whatever CultureInfo object is known by your system.
Composite.Core.ResourceSystem.StringResourceSystemFacade is used for getting strings at runtime that matches the CultureInfo your request is running in. Use this, instead of hardcoding strings on your pages or in your templates.
Read more about Localization here http://docs.composite.net/C1/HTML/C1-Localization.aspx
Global events
Composite.C1Console.Events.GlobalEventSystemFacade is important to know if you need to keep track on when the system is shutting down so you can make last-minute changes. Since C1 is highly multithreaded its easy to write extensions and modules for C1 that are multithreaded as well, taking advantage of multi core systems and parallelization and therefor its also crucial to shut down ones threads in a proper manner. The GlobalEventSystemFacade helps you do that.
Startup events
If you write plug-ins these can have a custom factory. Other code can use the ApplicationStartupAttribute attribute to get called by the Composite C1 core when the web app start up.
Data events
You can subscribe to data add, edit and delete events (pre and post) using the static methods on Composite.Data.DataEvents<T>. To attach to these events when the system start up, use the ApplicationStartupAttribute attribute.
Data
Composite.Core.Threading.ThreadDataManager is important if your accessing the Data Layer outside of a corresponding C1 Page request. This could be a custom handler that just has to feed all newest news as a Rss feed, or your maybe writing a console application. In these cases, always remember to wrap your code that accesses the data like this
using(Composite.Core.Threading.ThreadDataManager.EnsureInitialize())
{
// Code that works with C1 data layer goes here
}
For accessing and manipulating data its recommended NOT to use the DataFacade class, but wrap all code that gets or updates or deletes or adds data like this
using(var data = new DataConnection())
{
// Do things with data
}
IO
When working with files and directories its important to use the C1 equivalent classes Composite.Core.IO.C1File and Composite.Core.IO.C1Directory to .Net's File and Directory. This is due to the nature where C1 can be hosted on Azure, where you might not have access to the filesystem in the same way as you have on a normal Windows Server. By using the C1's File and Directory wrappers you can be sure that code you write will be able to run on Azure as well.
C1 Console
The console is a whole subject on itself and has many many API's.
You can create your own trees using Composite.C1Console.Trees.TreeFacade or Composite.C1Console.Elements.ElementFacade and implementing a Composite.C1Console.Elements.Plugins.ElementProvider.IElementProvider.
You can use the Composite.C1Console.Events.ConsoleMessageQueueFacade to send messages from the server to the client to make it do things like open a message box, refreshing a tree, set focus on a specific element, open a new tab etc. etc.
Composite.C1Console.Workflow.WorkflowFacade is used for getting instances of specific workflows and interacting with them. Workflows is a very fundamental part of C1 and is the way multi-step operations are defined and executed. This makes it possible to save state of operation so ie. a 10 step wizard is persisted even if the server restarts or anything else unexpected happens. Workflows are build using Windows Workflow Foundation, so are you familiar with this, you should be feeling at home
There is also a wealth of javascript facades and methods you can hook into when writing extensions to the Console. Much more than i could ever cover here so i will refrain myself from even getting started on that subject here.
composite.config
A fundamental part of C1 is providers, almost everything is made up of providers, even much of the core functionality. Everything in the console from Perspectives to Trees and elements and actions are feeded into C1 with providers. All the standard functions, the datalayer and all the widgets for use with the Function Call editor is feeded into C1 with providers. All the localisation strings for use with the Resources, users and permissions, url formatters etc. is all providers.
Composite.Data.Plugins.DataProviderConfiguration
Here all providers that can respond to the methods on DataFacade, Get, Update, Delete, Add etc. are registered. Every provider informs the system which interfaces it can interact with and C1 makes sure to route all requests for specific interfaces to their respective dataproviders.
Composite.C1Console.Elements.Plugins.ElementProviderConfiguration
Here we're defining the perspectives and the trees inside the Console. All the standard perspectives you see when you start the Console the first time are configured here, no magic or black box involved.
Composite.C1Console.Elements.Plugins.ElementActionProviderConfiguration
Action providers are able to add new menuitems to all elements in the system, based on their EntityToken. This is very powerful when you want to add new functionality to existing content like versioning, extranet security, custom cut/paste and the list goes on.
Composite.C1Console.Security.Plugins.LoginProviderConfiguration
A LoginProvider is what the C1 console will use to authenticate a user and let you log in or not. Unfortunately this isn't very open but with some reflection you should be all set.
Composite.Functions.Plugins.FunctionProviderConfiguration
Composite C1 will use all the registered FunctionProviders to populate its internal list of functions on system startup.
Composite.Functions.Plugins.WidgetFunctionProviderConfiguration
WidgetProviders are used in things like the Function Call Editor or in Forms Markup to render custom UI for selecting data.
Composite.Functions.Plugins.XslExtensionsProviderConfiguration
Custom extensions for use in XSLT templates are registered here
And then we have a few sections for pure configuration, like caching or what to to parallelize but its not as interesting as the providers.
Defining and using sections
Sections in composite.config, and other related .config files are completely standard .Net configuration and obeys the rules thereof. That means that to be able to use a custom element, like ie. Composite.Functions.Plugins.WidgetFunctionProviderConfiguration it has to be defined as a section. A section has a name and refers to a type that would inherit from System.Configuration.ConfigurationSection. Composite uses the Microsoft Enterprise Libraries for handling most of these common things like configuration and logging and validation and therefor all Composites sections inherit from Microsoft.Practices.EnterpriseLibrary.Common.Configuration.SerializableConfigurationSection. Now, this type just has to have properties for all the elements we want to be able to define in the .config-file, and .Net will automatically make sure to wire things up for us.
If you want to access configuration for a particular section you would call Composite.Core.Configuration.ConfigurationServices.ConfigurationSource.GetSection(".. section name") and cast it to your specific type and your good to go.
Adding extra properties to already defined sections
Normally .Net would complain if you write elements or attributes in the .config files that aren't recognized by the type responsible for the section or for the element. This makes it hard to write a truly flexible module-system where external authors can add specific configuration options to their providers, and therefor we have the notion of a Assembler. Its a ConfigurationElement class with a Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ObjectBuilder.AssemblerAttribute attribute assigned to it that in turns takes a Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ObjectBuilder.IAssembler interface as argument that is responsible for getting these custom attributes and values from the element in the .config file and emit usable object from it. This way .Net won't complain about an invalid .config file, since we inject a ConfigurationElement object that has properties for all our custom attributes, and we can get hold of them when reading the configuration through the IAssembler
Slides
Some overview slides can be found on these lins
Overview
Extensibility points
Page request handling
Function system
Data system
Data type system
Inspiration and examples
The C1Contrib project on GitHub is a very good introduction how to interact with the different parts of C1. Its a collection of small packages, that can be used as it is, or for inspiration. There are packages that manipulates with dynamic types to enable interface inheritance. Other packages uses the javascript api in the console, while others show how to make Function Providers, Trees and hook commands unto existing elements. There is even examples of how to manipulate with the Soap webservice communication going on between client and server so you can make it do things the way you want it. And the list goes on.
Is there any way i can load a silverlight application from isolated storage and replace the current application ?
Short answer: no, you cannot do this. You could however store a dll, read and load it via reflection if you are in a trusted out-of-the-browser application.
Anyway I don't believe this to be a very good practice, it's very likely there is a different better way to solve your particular problem.
You can't replace the currently running application from within Silverlight code.
However you could create a single application to act as a shell. You could store assemblies or entire Xaps in isolated storage. Using the AssemblyPart class allows you to load an assembly from this storage, create an instance of an entry type and execute an entry point method.
The big caveat would be that this "stored application" would have to be coded specifically to work within your shell. You would need to provide your ways in particular to allow for "application" level state to be accessed and a means of loading content assets such as images.
We've got a Qt application that configures external devices by querying their configure interface and then, using a QWebView, we present an HTML page with the appropriate controls. We'd prefer to hand the configuration information to some sort of Qt "Form Builder" class, and have it spit out a QWidget with a layout that contains native Qt controls. (We fully own the interface information, and so can turn it into whatever format this mythical "QFormBuilder" takes.)
Is this possible? No one really wants to budget the time to write our own parser (or use QScript for the same reason), as the HTML version looks "good enough". However, if there is an alternative, I'd love to know what other people have done.
Yes, that's possible. You can write the UI information in the same format Qt Designer uses, then construct the UI at runtime using the QUiLoader class.