Introduction

First of all, I have to say that this isn't my idea, it is more a portation of a C++ example to C# using a different way. If you want to get to the original article, click here. (Thanks to Igor Tolmachev for the nice idea.) I changed the way it works (from multiple dialogs to a single form) and added some new features (e.g. Rotation, Scaling, etc.).

Using the Program

Simply run the executable. To close the program, double click on the tray icon representing a snow flake.

Using the Code

The program itself uses a non-bordered form (which is resized to match screen resolution) with a transparent background color for drawing the snow flakes. Instead of using several forms/dialogs (I hate this idea), I just use one form on which I draw using GDI+.

 public MainForm() {
    InitializeComponent();

    //We paint our control ourself 
    //and need a double buffer to prevent flimmering
    SetStyle(
        ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint |
        ControlStyles.DoubleBuffer, true);

    //Resize and relocate form to match Screen settings
    Location = new Point(Screen.PrimaryScreen.Bounds.X, 
                 Screen.PrimaryScreen.Bounds.Y);
    Width = Screen.PrimaryScreen.Bounds.Width;
    Height = Screen.PrimaryScreen.Bounds.Height;
 }

The snowflakes themselves are saved in a List<SnowFlake>. Snowflake is a container class containing the current Data/Positions of the snowflake (X, Y, Rot, Scale) and the Velocities/Changes (XVel, YVel, RotVel)

The main function is the OnTick method, which is divided into several steps:

Increasing the tick count (e.g. Adding snow flakes every tick would be a bit too much)
Spawning new flakes (If appropriate conditions are given)
Moving all flakes (by adding the velocities to the data values)
Deleting flakes which are below the screen/taskbar
Rendering the flakes

The flakes are drawn by defining a userpaint method MainForm_Paint and calling Refresh() to cause the form to invalidate itself. Refresh() is required, as it supports double buffers, which MainForm_Paint(CreateGraphics()) would not. In this case, I used the Matrix capabilities of GDI+ to rotate and scale the snowflakes.

 foreach (SnowFlake s in SnowFlakes) {
    g.ResetTransform();
    g.TranslateTransform(-16, -16, MatrixOrder.Append); //Align our flakes to the center
    g.ScaleTransform(s.Scale, s.Scale, MatrixOrder.Append); //Scale them..
    g.RotateTransform(s.Rotation, MatrixOrder.Append); //Rotate them..
    //Move them to their appropriate location    
    g.TranslateTransform(s.X, s.Y, MatrixOrder.Append); 
    g.DrawImage(Snow, 0, 0); //draw them
 }

The snowflake image is drawn by using the GDI+ functions and then cached at a 32x32 pixel size for performance reasons. (GDI+ is slow when you draw lots of lines.)

Customize!

You could get some pretty nice results by just increasing the snow flake spawn count/the velocities. But note that GDI+ is not as fast at it may look and it increases CPU usage (especially when using matrices).

History

3^rd October, 2007: Initial post

(Desktop) Falling Snowflakes