I was in a “star” mood this afternoon and created this Silverlight 2.0 demonstration.

For rendering it uses the CompositionTarget.Rendering method (the easiest way to control dynamic animations such as this). It also uses the VisualStateManager in a variety of places to control the user interface. I’ve become a big fan of the VSM – it’s easier to use than what WPF has as of 3.5 SP1 (I know it’s coming to WPF as well).

If you click into the UI to give it focus, you can press the [F] key to go full screen.

Switching to full screen is simple:

SilverlightHost host = Application.Current.Host;
if(host != null)
{
    Content content = host.Content;
    content.IsFullScreen = true;
}

I’ve also used my ToColorFromHex function liberally (I used Kuler to make some colors and grabbed their hex values and directly pasted into my source code).

To create the star trails (as I’ve called them), I needed to do a little bit of trigonometry:

double radians = Math.Atan2(-star.Vector2D.Y, -star.Vector2D.X);
(star.StarTrailUI.RenderTransform as RotateTransform).Angle = radians * 180 / Math.PI;

I used a RenderTransform in place of building a line with the proper X & Y coordinates as it made dealing with the LinearGradientBrush on the trail a TON easier (for me at least).

Demonstration

I’ve provided all of the source code – maybe you’ll find it useful (if so, I’d like to hear about it!).

Source code

Update: Fixed the links. Sorry!

Silverlight 2.0 is missing a ColorConverter. There’s no easy and efficient way from code to convert from a HEX color format to a built in Color type. I like being able to paste standard web color formats into my source code without converting them to a Color.FromArgb byte format (as most web color selectors support that format).

I wrote this code to end this annoyance (but didn’t bother with a full-fledged TypeConverter):

public static class Extensions
{
    public static void SetFromHex ( this Color c, string hex )
    {
        Color c1 = ToColorFromHex(hex);

        c.A = c1.A;
        c.R = c1.R;
        c.G = c1.G;
        c.B = c1.B;                        
    }

public static Color ToColorFromHex ( string hex )
{
    if(string.IsNullOrEmpty(hex))
    {
        throw new ArgumentNullException("hex");
    }

    // remove any "#" characters
    while(hex.StartsWith("#"))
    {
        hex = hex.Substring(1);
    }

    int num = 0;
    // get the number out of the string 
    if(!Int32.TryParse(hex, System.Globalization.NumberStyles.HexNumber, null, out num))
    {
        throw new ArgumentException("Color not in a recognized Hex format.");
    }

    int[] pieces = new int[4];
    if(hex.Length > 7)
    {
        pieces[0] = ((num >> 24) & 0x000000ff);
        pieces[1] = ((num >> 16) & 0x000000ff);
        pieces[2] = ((num >> 8) & 0x000000ff);
        pieces[3] = (num & 0x000000ff);
    }
    else if(hex.Length > 5)
    {
        pieces[0] = 255;
        pieces[1] = ((num >> 16) & 0x000000ff);
        pieces[2] = ((num >> 8) & 0x000000ff);
        pieces[3] = (num & 0x000000ff);
    }
    else if(hex.Length == 3)
    {
        pieces[0] = 255;
        pieces[1] = ((num >> 8) & 0x0000000f);
        pieces[1] += pieces[1] * 16;
        pieces[2] = ((num >> 4) & 0x000000f);
        pieces[2] += pieces[2] * 16;
        pieces[3] = (num & 0x000000f);
        pieces[3] += pieces[3] * 16;
    }
    return Color.FromArgb((byte) pieces[0], (byte) pieces[1], (byte) pieces[2], (byte) pieces[3]);
}

}

 

It accepts 3 standard formats for colors:

1. [ALPHA][RED][GREEN][BLUE] (alpha and all colors)
2. [RED][GREEN][BLUE] (no alpha channel, automatically set to 255)
3. Short hand [R][G][B] (takes the single digit hex number and adds it to the same number * 16, alpha set to 255);

To use the function:

Color c1 = Extensions.ToColorFromHex("#00B2D6E8");

Obviously the built in components, brushes, etc. support that format already, but there doesn’t seem to be any place that functionality is exposed.