WINDOWS CE R3 Silverlight for Embedded tutorial

    </Grid>
</UserControl>
We have a top level container (UserControl) that uses a Grid layout (objects are organized in rows and columns) and contains our button.
The button has attributes for placement inside its own grid cell (the only one we have), alignment, content (the text "Button") and its name ("MyButton").
Now we can start Platform Builder and add a new subproject to our OS Design.
You may develop your Silverlight for Embedded application also using Visual Studio 2005 or 2008 Smart Device application if you generate an SDK from your R3 OS design and install it on your development PC, but for this tutorial we will keep things simple...
Move to the solution tab, right click on the subprojects node and select "add new...".
Create a Win32 application.

And choose the simple Win32 application template.

This will create an application containing only WinMain, it's enough to start experimenting with our first Silverlight for Embedded UI.
The first thing we should do is add the Silverlight for Embedded includes to our source code:

#include "pwinuser.h"

#include "xamlruntime.h"

#include "xrdelegate.h"

#include "xrptr.h"

We will add the XAML that we generate with expression blend to our application resources. In this way we will not need to distibute the XAML file with it. On the other side changes to the XAML will require a rebuild of the application, you may choose the best method to integrate XAML and C++ source code in your application.
To include resources inside your executable file you need to add a resource script (rc file) to your subproject.
Right click on the subproject in solution view, select "add\new item" and then select resource file from the dialog box and assign a name to it (usually you have only one resource file per application so using the application name for that file sounds like a good idea).

Now that you have your resource file you can add the XAML data to it by creating a new resource.
Go to the "resource view" tab, right click on your resource file and select "add resource..."

Now you can import your XAML file data inside your executable. It will be stored inside it (at the end of the file) as binary data.

Type "XAML" as resource type.

For the tutorial you can leave the default ID (IDR_XAML1) for that resource, but it's a good idea to give meaningful names to your XAML components in a real project.

To use our resource IDs we need to include "resource.h" inside our .cpp file:

#include "resource.h"

Then, inside our application main function (WinMain) we can start to interact with the XAML runtime.
First of all we need to initialize it:

    if (!XamlRuntimeInitialize())

        return -1;

If XamlRuntimeInitialize succeeded, the Silverlight for Embedded runtime is loaded inside your application and it's ready to handle the UI.
Each Silverlight for Embedded application has a singleton "Application" object that allows us to access global application properties and features.
To access it we should use the GetXRApplicationInstance API.

    HRESULT retcode;

    IXRApplicationPtr app;

    if (FAILED(retcode=GetXRApplicationInstance(&app)))

        return -1;

Someone will notice that we are using HRESULTs and classes that use the "I" prefix and the "Ptr" suffix and understand that this new technlogy is based on COM (Component Object Model) that may sound like an ancient tool in those .NET and managed code days but it's still the foundation of many technlogies on both CE and desktop Windows releases. All Silverlight for Embedded objects are implemented as COM objects that export specific interfaces (COM interfaces have names beginning with "I"). Since using interfaces directly requires handling of their reference count and this may lead to memory leaks or premature object deletions, COM programmers prefer to use "smart pointers" that are wrappers around the interfaces and manage reference counting internally, destroying the COM object when the smart pointer object goes out of scope inside your C++ application (function return if it's allocated on the stack, object destruction if it's declared as a class member etc.). Smart point classes add the "Ptr" suffix to the interface name.
After this 30 seconds introduction to COM, we can return to our application.
The first thing we have to do with our application object is tell it where it can find its resources (XAML, images etc.).
We included them inside the executable using the resource file and so we can pass our HINSTANCE handle to it:

    if (FAILED(retcode=app->AddResourceModule(hInstance)))

        return -1;

Now that we have initialized our application object we can create our main window and let Silverlight for Embedded manage its contents:

    XRWindowCreateParams wp;

    ZeroMemory(&wp, sizeof(XRWindowCreateParams));

    wp.Style       = WS_OVERLAPPED;

    wp.pTitle      = L"S4E Test";

    wp.Left        = 0;

    wp.Top         = 0;

    XRXamlSource xamlsrc;

    xamlsrc.SetResource(hInstance,TEXT("XAML"),MAKEINTRESOURCE(IDR_XAML1));

    IXRVisualHostPtr vhost;

    if (FAILED(retcode=app->CreateHostFromXaml(&xamlsrc, &wp, &vhost)))

        return -1;

The VisualHost object "hosts" the runtime and allows us to access its contents and load our XAML from resources (using the XRXamlSource object).
Now our XA
The object inside our Silverlight for Embedded application are organized in a objects tree. To access the object inside it we need a pointer to its root:

    IXRFrameworkElementPtr root;

    if (FAILED(retcode=vhost->GetRootElement(&root)))

        return -1;

From the root object we can access our button using the name we assigned to it inside Expression Blend:

    IXRButtonBasePtr btn;

    if (FAILED(retcode=root->FindName(TEXT("MyButton"), &btn)))

        return -1;

To receive a notification when the user clicks our button we need to provide a delegate. A delegate is a pointer to a member of an istance of a C++ class that should have a specific prototype.
We can declare a simple C++ class inside our .cpp source and implement our button click event delegate inside it:

class BtnEventHandler

{

public:

    HRESULT OnClick(IXRDependencyObject* source,XRMouseButtonEventArgs* args)

    {

        MessageBox(NULL,TEXT("Click!"),TEXT("Silverlight for Embedded test"),MB_OK);

        return S_OK;

    }

};

Our event handler will simply display a message box when the button is clicked.
As you can see the event handler takes two parameters. A pointer to the object that generates the event (our button) and a pointer to a structure that contains the event parameters.

To connect our event handler to the button we have to create a delegate object:

    BtnEventHandler handler;

    IXRDelegate<XRMouseButtonEventArgs>* clickdelegate;

    if (FAILED(retcode=CreateDelegate(&handler,&BtnEventHandler::OnClick,&clickdelegate)))

        return -1;

    if (FAILED(retcode=btn->AddClickEventHandler(clickdelegate)))

        return -1;

Our event handler has been connected to the button, now we can show our UI and wait that the user presses our wonderful button:

    UINT exitcode;

    if (FAILED(retcode=vhost->StartDialog(&exitcode)))

        return -1;

Our clickdelegate object is not a smart pointer, so we will have to release it explicitly:

    clickdelegate->Release();

Before we can build our subproject we need to add the include directories and the libraries needed to support Silverlight for Embedded inside our application.
Open the subproject sources script by right clicking on the subproject and choosing "open".
Add includes:

INCLUDES=$(_OEMINCPATH)

and libraries:

TARGETLIBS= \

    $(_PROJECTROOT)\cesysgen\sdk\lib\$(_CPUINDPATH)\coredll.lib \

    $(_PROJECTROOT)\cesysgen\sdk\lib\$(_CPUINDPATH)\xamlruntime.lib \

    $(_PROJECTROOT)\cesysgen\sdk\lib\$(_CPUINDPATH)\uuid.lib \

(you should already have the TARGETLIBS directive inside your sources script)
Now you can run the application on your device and push that button!

You, like me, are too lazy to type sample code, you can download a zip containing our demo application here:
http://cid-9b7b0aefe3514dc5.skydrive.live.com/self.aspx/.Public/SilverlightSample.zip