FGF: Modules, Not Components

As you no doubt saw in the writing of the Application class, FGF implements its own version of the XNA Framework’s component classes. The first major reason for doing so is that the builtin component classes require you to pass in a (Framework) Game object through the constructor. While this dependency can be circumvented by implementing the interfaces directly and supplying a manual workaround, the attempt is exactly that: a workaround. The second major reason for my implementation is that by controlling the interfaces and base classes, I can easily support more advanced situations such as the separation between initialization and content loading/unloading. You will see more of this later on when I modify the classes to support asynchronous content loading.

For now, the focus is being put on building a robust base for developers to start working with my framework. Because the goal is to fix the XNA Framework’s implementation, we begin with a simplification of the IGameComponent, IUpdateable and IDrawable interfaces. We combine these three into a single, multi-purpose interface, IModule.

public interface IModule
{
    event EventHandler DrawOrderChanged;
    event EventHandler UpdateOrderChanged;

    void Initialize(IGame game);

    void Draw(GameTime gameTime);
    void Update(GameTime gameTime);

    int DrawOrder { get; }
    int UpdateOrder { get; }

    bool IsVisible { get; set; }
    bool IsEnabled { get; set; }
    bool IsInitialized { get; set; }

    IModule Parent { get; set; }
    ModuleCollection Modules { get; }
}

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FGF: A Collection Class with Events

For most purposes, the builtin collection classes supplied by the .NET Framework are terrific. They are simple and straight forward implementations that do exactly as you expect. But for our purposes, a collection class that fires events when the collection is changed is simply better and in some cases, necessary. For this class, we make the jump over to the FocusedGames.Collections namespace, maintained in the FocusedGames library.

Before writing the collection class itself, we need a delegate that can define how our events will work. Enter the CollectionChangedHandler delegate.

public delegate void CollectionChangedHandler(object sender, CollectionChangedEventArgs args);

As you can see, we need to define the CollectionChangedEventArgs class itself. This is a simple class that has two properties. The two properties help listeners of the events to understand how the collection was changed.

public class CollectionChangedEventArgs : EventArgs
{
    public CollectionChangedEventArgs()
    {
    }

    public CollectionChangedEventArgs(object item)
    {
        Item = item;
    }

    public CollectionChangedEventArgs(object item, int index)
        : this(item)
    {
        Index = index;
    }

    public object Item { get; set; }
    public int Index { get; set; }
}

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FGF: A Base Class For INotifyPropertyChanged

One piece of functionality I consistently find myself writing and rewriting is the implementation of the INotifyPropertyChanged interface. This class, located in the main FGF library, makes that rewriting unnecessary by implementing it in an open way.

public class NotifyPropertyChangedBase : INotifyPropertyChanged
{
    private bool isDirty = false;

    public event PropertyChangedEventHandler PropertyChanged;

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FGF: Oriented Drawing

After you’ve read about the Display Orientation features of FGF, a natural question to ask is “How do I draw and take input with a rotated display?” Fortunately FGF has some methods to help in this department that sit alongside the rotation methods and properties in the Application class.

Application.OrientedDisplaySize

If you need to draw something relative to the size of the screen, use the OrientedDisplaySize property of the Application class. This property differs from DisplaySize, which is used to change the actual size of the display, in that OrientatedDisplaySize reacts to the selected rotation of the display, set with the DisplayOrientation property.

DisplaySize = new Vector2(272, 480);
DisplayOrientation = DisplayOrientation.Rotated;

Console.WriteLine(OrientedDisplaySize.ToString());

Because the display is set to be rotated (landscape on the Zune HD), the above code will actually print out a display size of (480, 272) rather than the standard (272, 480) size.

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FGF: Display Orientation on the Zune HD

New in the Focused Games Framework is the support for rotating and resizing the display on the fly. The main reason for this functionality is for mobile platforms like the Zune HD that support games in a landscape mode as well as a portrait mode. Supporting either in your game is made easy with FGF-you just need to know the right properties. In the standard display mode, the Zune HD has a display resolution of 272 pixels by 480 pixels. In landscape mode those two measurements are switched: 480 pixels by 272 pixels. While it is important to know the standard resolution, mucking about with a render target and backbuffer size is no longer necessary.

The one hitch? Your game class needs to inherit from FocusedGames.Xna.Application instead of Microsoft’s Game class. The following code block sets a Zune HD game up for landscape rendering.

public class Game1 : Application
{
    public Game1()
    {
        // Set the display size and the rotation
        DisplaySize = new Vector2(272, 480);
        DisplayOrientation = DisplayOrientation.Rotated;
    }

    // ...
}

Note that to keep the device in portrait mode, you don’t need to change the value of DisplayOrientation but setting the DisplaySize property to the standard value is a good idea. Happy landscaping!

Provider Model – Design Pattern

A design pattern made famous in the .NET community by Microsoft’s ASP.NET, the provider model explains is a pattern that supplies the end-developer with a plug-and-play architecture. The provider model is most often used when you have a consumer object that is dependent on specific functionality that can be supplied by one or more underlying systems. The major benefit of which is an increase in manageability and reusability.

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Re: Will Silverlight fix the web…?

It disgruntles me when poor arguments are put forth. For instance, Silverlight should be avoided is an argument that relies on a very biased opinion rather than fact. The problem, of course, isn’t that the argument is being made against Silverlight but rather that the argued points are unfounded and poorly written. Below is a point-by-point analysis and counter-point piece based on what I know of Silverlight as well as what Bing can tell me.

Hyperlinks

The author chooses, of course with no evidence, to make the point that Silverlight doesn’t support deep linking. I agree that providing a uri for each page, document, video, et cetera, is an important part of what makes the web accessible. Anyone who has visited an all Flash site from the late 90′s knows why: without a Uri, users cannot gain quick and consistent access to content. It is fortunate that Silverlight provides deep linking support, otherwise I would have to agree with the author. A quick Bing or Google search could have provided the author with this information, but then again what are facts to an argument?

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FGF: A Helper For Creating Render Targets

Before I begin this post, big thanks to Eibx and David over at the Community Forums for helping me find these methods. I have modified the CheckTexture method a bit, but its purpose remains unchanged.

As of the last FGF article, the Application class was implementing the IGame interface but was missing the ability to create a render target object on the PC and Xbox 360. For PC games this can be a troubling problem since different hardware can obviously require different formats and dimensions of render target. Rather than bake this functionality into the Application class itself, it is moved to a static helper class so that all developers can make good use of its functionality at any point in time.

To start off, a simple default creation method is included to give the basic functionality an easy access point.

using System;

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace FocusedGames.Xna.Graphics
{
    public static class GraphicsHelper
    {
        public static RenderTarget2D CreateRenderTarget(GraphicsDevice device)
        {
            return CreateRenderTarget(
                device,
                device.PresentationParameters.BackBufferWidth,
                device.PresentationParameters.BackBufferHeight,
                1,
                device.PresentationParameters.BackBufferFormat
            );
        }

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FGF: It’s All About Abstraction

One of the major themes present in the design of FGF is abstraction of functionality from its implementation. The major reason for this is because one of the major goals of FGF is to provide functionality without forcing developers into a corner. The idea is if the base of the framework is modular and open, the rest of the framework will fall into place very easily. So I begin the implementation of FGF by fixingimproving the XNA Framework’s Game class with an abstraction of its functionality. The reason for which will become apparent when the component classes are improved at a later time.

The important question to ask here is what can a game do? We can run a game, and exit a game but also add and remove components and services. Thus the IGame interface is born (within the FocusedGames.Xna project):

using Microsoft.Xna.Framework;

namespace FocusedGames.Xna
{
    public interface IGame
    {
        void Run();
        void Exit();

        Vector2 ObjectToScreen(Vector2 objectVector);
        Vector2 ScreenToObject(Vector2 screenVector);

        GraphicsDeviceManager DeviceManager { get; }

        DisplayOrientation DisplayOrientation { get; set; }
        Vector2 DisplaySize { get; set; }

        bool IsLoaded { get; }

        float TargetFrameRate { get; set; }

        ModuleCollection Modules { get; }
    }
}

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