This is from the most recent build of FGF:
Yes, it is my own implementation of the Aero style of windows done in XNA. What does this mean? Well I have decided that although the simple way of doing a menu system in games is fine for simple situations, I want something more powerful and prettier to look at. Thus I have started working on a new UI library for Thrust that is based on Aero and similar interfaces. I am doing it in a fully customizable but lightweight manner and working on Xbox 360 compatibility.
This is a fundamental topic in C# and if you plan to do any development at all with the language you need to know this. Override is used for changing the behavior of the original type’s method or property. The new keyword, in this case, is used for scratching the existing behavior but only in the current type. To better explain this, consider the following code.
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| public class Foo{
public virtual void Print(){
Console.WriteLine("I am a Foo!");
}
}
public class Bar{
public override void Print(){
Console.WriteLine("I am a Bar!");
}
} |
If we declare a Bar and cast it to a Foo in the above code, we will still get “I am a Bar!” when we invoke the Print method. However, if we change the code to the following things will get messed up a bit.
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| public class Foo{
public void Print(){
Console.WriteLine("I am a Foo!");
}
}
public class Bar{
public new void Print(){
Console.WriteLine("I am a Bar!");
}
} |
If we instantiate a Bar, we will get the new functionality. However, if we cast that Bar object into a Foo, we will get the implementation provided by the Foo. So be sure of what you are using and why!
Today, while coding Galactic Wars v2.0, I stumbled upon a problem I have been having with content since I started working with XNA. The following diagram shows how easy it is to create the problem and how devastating it can be to any application. In my case, I have two (or more) menus that are referencing a piece of content.
Each menu references the same managed object which is really a wrapper for a second managed object (Texture2D in this case). The second object is a managed wrapper for the underlying unmanaged data, again in this case it is texture data. The problem is when one menu is being phased out (unloaded) and another is being phased in (loaded). The menu being loaded grabs a reference to the content before the other menu can unload it. The ordering is done this way to ensure that a menu actually loads its content before the current menu is unloaded.
After the menu is done loading content, the second menu is unloaded which drops the content and releases the unmanaged memory. Aha! The problem stems from the last point: I am trying to manage unmanaged memory when I should just let the GC take care of it. The reason I do this is for performance reasons, primarily on the Zune. Instead of letting textures just sit around, I release them when they are no longer needed to avoid piling up the garbage.
So what is the solution?
- Dereference the Managed Object
I would love to do this but unfortunately it introduces a second problem. If every menu (object using the content) dereferences the asset, it still will not be collected by the GC. The AssetManager still holds a reference which is now being unused and thus memory is wasted. The upside to this is that I do not need to implement the second option…
- Reference Counting!
By implementing a counter on the asset itself and asking developers to always call Unload or Unload(ILoadable) on the AssetManager, I can guarantee that no Asset will be disposed while another object is using it. The downside is that it is an ugly implementation of something that is done in the GC anyways. The major upside is that even if developers use the previous method, the GC will still eventually catch the wasted memory.
So now Thrust’s AssetManager and IAsset require (and implement) reference counting to avoid the problem described above. And it works wonderfully.
The provider model’s goal is to allow for the abstraction of implementation to the nth degree by allowing for the choice between separate implementations of the same functionality. This design pattern is incredibly common in Microsoft’s ASP.NET, especially in the realm of security. Developers can choose between different providers for membership, roles and authentication for a single site. The point is that the core functionality of the site does not change, only the implementation. Below is a quick snapshot of how such a model is used in Vodka.
The driving force behind the provider model is the abstraction of the implementation. This is done via an interface.
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| public interface IAuthenticationProvider{
bool Authenticate(string username, string password);
} |
What gives the provider model its meat and bones is the different implementations of the above interface. The two implementations below represent two authentication backends: an ActiveDirectory installation and an Sql database. Although the meat has been stripped from these two classes, it is clear that their implementations would differ enough to have the two separate classes. Read more »
Looks like Mono 2.0 is out. Dot NET development just got a little better (on Linux)!
Off topic, but anyone notice that in the second episode of the first season of West Wing a character by the name of Mandy runs her BMW E36 M3 right over a curb? Poor BMW… 
It was a convertible too!
Ugh. It frustrates me how some companies can leave out even the most basic of functionality, like disabling the editing engine so you can edit XML straight like the following shows:
My senior project involves the study of highly extendible systems for the internet, mainly content management systems/solutions. I am building mine in ASP.NET 3.5 on WS2008, SQL2008 and .NET 3.5 (which includes WCF). The goal is to build a system that has plug-and-play services and is both quick and easy to use. Today I got the very first part of this system up and running and can be reached at jsedlak.homedns.org.
There is a lot of work to be done, but the base code (being built into FGF) is coming along very nicely. Once I can figure out security, the project should simply expand exponentially provided I have the time (ugh!). The two main [sub]projects here are FGDN (Focused Games Developer Network) and a simple CMS similar to that of WordPress, SharePoint, et al. The first is designed to allow users to submit bugs, feature requests, etc. easily much like Microsoft’s Connect. The latter is pretty self explanatory.
Because I am building this all as one interconnected solution, I have also started working on the idea that users that exist in Vodka [may] have access to many other parts of Focused Games. Primarily this means FGDN but also the SVN repositories. A user (you) can apply for access to one or more of the repositories I currently use for my source code. Once you are accepted, you are also connected to any other Vodka service I create. Pretty nifty, eh?
I was pushing Galactic Defense to the Zune today to do some minor version testing (I develop on the PC and then push to Zune for platform specific tests) and ran into some major problems. The GC was collecting about once an update which was slowing the game down tremendously. So I dug in and started searching my code.
One of the best ways to figure out where you are creating garbage (when no tool can do it for you) is just to start commenting things out. For starters, I commented out the draw code for my map. This worked, but not enough. I ended up adding a line that removed the InputManager from the component collection (effectively commenting out its update code) and I had it: 0 allocations per update.
So I looked at the draw code again and realized (with the help from guys in #xna) that I was using an enumeration in a Dictionary. A big no no since the framework allocates every time you do a lookup. A quick switch to ints (cast all lookups to integers) fixed that problem. Now onto the InputManager.
To make a long story short, I followed the trail and cornered this line of code:
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| if(!repeatKeys.Contains(button)) |
It is this line of code that actively makes sure that I have all the buttons in the repeatKey list so I can check and update the repeated keys later on. I removed this line of code and added the following:
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| bool found = false;
for (int i = 0; i < repeatKeys.Count; i++)
{
if (repeatKeys[i] == button)
{
found = true;
break;
}
}
if (!found)
repeatKeys.Add(button); |
And now I am back to a normal amount of allocations (some for strings) per update. I wonder why Contains is causing an allocation. I am too lazy to figure that one out right now…
Here is a quick screen cap of FGF opened in Visual Studio 2008. Got to love all the projects, right?
The Parallel Extensions for .NET was released yesterday. Parallel Extensions provides an easy way to develop software on multicore and multiple CPU hardware with a managed programming model.
We’re very excited to announce our 2nd Community Technology Preview (CTP) for Parallel Extensions to the .NET Framework 3.5. We released the Dec07 CTP on 11/29/2007, and from that we have received a lot of feedback from the community and customers. While you have been using our bits, participating in our forums, sharing your insights and experiences, and following along on our blog, we have been hard at work preparing this CTP, incorporating your feedback into it.
November 5, 2008 12:02 pm | 
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