Chris Cavanagh's Blog

Newton Physics Extensions for WPF

Chris Cavanagh — Wed, 09 Jul 2008 05:35:28 +0000

Here’s something you’ll want to check out… Leslie Godwin has written some WPF extensions for the Newton Game Dynamics engine - the same physics engine I used in one of my first demos (the sweet one with the car). Although the resulting moon lander demo is HARD (my landing gear kept snapping off), Leslie’s description of building it (including using Blender and exporting a model to XAML) is definitely worth reading; even more so if you’re into this stuff

Silverlight soft-body physics

Chris Cavanagh — Tue, 24 Jun 2008 19:29:41 +0000

Here’s a simple soft body physics demo based on Walaber’s excellent JelloPhysics library. It enjoys my trademark boring user interface (umm, so it doesn’t detract from the coolness of the physics):

Click the image above or follow this link (you’ll need Silverlight 2 beta 2). If the platforms are scattered too much, just click the “Move platforms” button.

JelloPhysics is also the engine behind Walaber’s awesome Jellycar game (PC version here).

Source code will be available once I’ve made a few improvements

Enjoy!

LINQPad - Copy HTML to clipboard

Chris Cavanagh — Mon, 23 Jun 2008 15:54:03 +0000

Here’s a useful bit of C# you can paste into your LINQPad statements to quickly hack together some HTML (could be useful for quick ad-hoc database reports):

Action<string, string> HtmlToClipboard = delegate( string htmlFragment, string title )
{
    Func<int, string> To8DigitString = delegate(int x) { return String.Format("{0,8}", x); };

    if (title == null) title = "From Clipboard"; 

    var sb = new System.Text.StringBuilder();
    var header = @"Format:HTML Format
Version:1.0
StartHTML:<<<<<<<1
EndHTML:<<<<<<<2
StartFragment:<<<<<<<3
EndFragment:<<<<<<<4
StartSelection:<<<<<<<3
EndSelection:<<<<<<<3
";

    var pre = @"
" </span><span style="color:black;">+ title + </span><span style="color:#dc1414;">@"";

    var post = @"";

    sb.Append(header);
    int startHTML = sb.Length;

    sb.Append(pre);
    int fragmentStart = sb.Length;

    sb.Append(htmlFragment);
    int fragmentEnd = sb.Length;

    sb.Append(post);
    int endHTML = sb.Length;

    sb.Replace("<<<<<<<1", To8DigitString(startHTML));
    sb.Replace("<<<<<<<2", To8DigitString(endHTML));
    sb.Replace("<<<<<<<3", To8DigitString(fragmentStart));
    sb.Replace("<<<<<<<4", To8DigitString(fragmentEnd));

    string data = sb.ToString();
    System.Windows.Forms.Clipboard.Clear();
    System.Windows.Forms.Clipboard.SetText(data, System.Windows.Forms.TextDataFormat.Html);
};

Note you’ll need to add a reference in LINQPad (Query -> Advanced properties) to System.Windows.Forms.dll (it uses the Clipboard class). For more detail on why it jumps through so many hoops, read this post by Mike Stall.

Silverlight 2 2D Physics updated

Chris Cavanagh — Mon, 16 Jun 2008 13:15:20 +0000

I’ve updated my Silverlight 2D Physics demo again, this time for Silverlight 2 Beta 2. You can preview it here and get the source here. Although all I did was recompile it, at some point in the past I exposed a bug in the BulletX physics engine (previously it had a workaround [hack] to prevent it blowing up). You might get the occasional “Index out of bounds” error and weird behavior (the wheels/heads might fall through the platforms, then throw you to a blank page!). I’ll update here when it’s fixed

SkinBuilder and data binding

Chris Cavanagh — Tue, 03 Jun 2008 16:14:11 +0000

I’ve updated my WPF SkinBuilder utility to fix a couple issues it had with data binding. The fix involved WPF’s equivalent of “Application.DoEvents”. This might be the most compact version of it yet:


Dispatcher.CurrentDispatcher.Invoke( DispatcherPriority.Background, (Action)delegate {} );

Basically it just blocks operation until all important processing is complete (anything with a DispatcherPriority higher than ‘Background’).

Conditional extension method

Chris Cavanagh — Thu, 22 May 2008 20:32:32 +0000

Here’s a nice little extension method you might find useful:

public static class ExtensionMethods
{
    public static T If(
        this bool condition,
        T left,
        T right )
    {
        return condition ? left : right;
    }
}

Looks pretty useless right? It is, unless you want to do something like this in C#:

Func<MyType, bool> predicate = myCondition
    ? v => ( v != null ) ? v.MyFlag : false
    : v => true;

Here’s where compilation will get you:

Type of conditional expression cannot be determined because there is no implicit conversion between ‘lambda expression’ and ‘lambda expression’

You can easily fix it by casting one of the expressions to the result type like this:

Func<MyType, bool> predicate = myCondition
    ? v => ( v != null ) ? v.MyFlag : false
    : (Func<MyType, bool>)( v => true );

But that’s just hideous, right? (it forces you to repeat yourself, it’s ugly and you can’t use ‘var’). Enter our super slick new extension method:

var predicate = myCondition.If<Func<MyType,bool>>(
    v => ( v != null ) ? v.MyFlag : false,
    v => true );

It’s not perfect, but it’s neater. You can even use it with expression trees:

var predicate = myCondition.If<Expression<Func<MyType,bool>>>(
    v => ( v != null ) ? v.MyFlag : false,
    v => true );

Improvements & comments welcome

More WPF Physics

Chris Cavanagh — Fri, 16 May 2008 02:45:37 +0000

Fabrice Kauffmann has started a series of posts on using a physics engine with WPF, with some good code samples to get you on the right track. You can read part 1 here, or in the original French here

Dead ringer

Chris Cavanagh — Tue, 06 May 2008 03:39:21 +0000

It was inevitable of course, but I’m comforted by the warranty

.NET is crap?

Chris Cavanagh — Mon, 05 May 2008 16:05:23 +0000

Wow, I can’t believe I still enjoy writing .NET apps on Windows when it’s this bad. How naive of me… Maybe I’m just old and get a kick from dumbed-down languages (btw I turned 100011 (0×23) yesterday; yay me! ).

System.Web.Routing with WebForms sample

Chris Cavanagh — Fri, 25 Apr 2008 22:29:33 +0000

UPDATE: You can see a sample site running here. As it’s using IIS6 I needed to add a Wildcard Application Mapping. Note this passes every request through ASP.NET; you might prefer some alternative options, or use IIS 7 where you get it for free.

Since my earlier post on using the System.Web.Routing assembly with traditional WebForms (here), I’ve had some requests for a sample project to show it in action. You can get the source right here.

This sample shows a way of getting the route information from the RouteHandler to the page, with minimal changes to existing pages (good if you’re migrating from a 3rd party URL rewriter). Basically the WebFormRouteHandler copies relevant routing values into the HttpContext.Items collection (so they’ll only exist for the lifetime of the current request). You can then grab these values in your WebForm.

For another example of passing routing details to a WebForm, see Phil Haack’s great post here.