C# Form Animation with Windows API

Introduction

This is my first ever article. I have been working with so many applications of-late but never thought of publishing any of my work online. I am referring to this site since long, and now I think it's pay back time for me.

Some Background

If you are familiar with Windows APIs, then you must be aware that they provide a great interface for developing out-of-the-box applications. There are so many of them available for use, but most of the time programmers hesitate to use them because there are some complexities involved in embedding them to the core application.

How To Use the Code

Just download and run the demo to see the animation in action.

How It Works

This article demonstrates the use of one of the Windows APIs called AnimateWindow. The API, among so many others is found in the user32.dll library. Detailed explanation of this API can be found here. A call to this API requires three arguments:

A handle to the window (form) to be animated
Animation duration (in milliseconds)
Some flags describing the type of animation

The purpose of this application is fairly simple. The application will demonstrate the form animation using the AnimateWindow API. There are two forms in this application. One provides the user with various options that can be used to animate any form. The other just shows the form animation effect in action.

I have created a separate class WinAPI which is used to declare the constants that are used when calling the API and the API itself. The code for this class looks like this:

public class WinAPI
    {
        /// <summary>
        /// Animates the window from left to right. 
        /// This flag can be used with roll or slide animation.
        /// </summary>
        public const int AW_HOR_POSITIVE = 0X1;
        /// <summary>
        /// Animates the window from right to left. 
        /// This flag can be used with roll or slide animation.
        /// </summary>
        public const int AW_HOR_NEGATIVE = 0X2;
        /// <summary>
        /// Animates the window from top to bottom. 
        /// This flag can be used with roll or slide animation.
        /// </summary>
        public const int AW_VER_POSITIVE = 0X4;
        /// <summary>
        /// Animates the window from bottom to top. 
        /// This flag can be used with roll or slide animation.
        /// </summary>
        public const int AW_VER_NEGATIVE = 0X8;
        /// <summary>
        /// Makes the window appear to collapse inward 
        /// if AW_HIDE is used or expand outward if the AW_HIDE is not used.
        /// </summary>
        public const int AW_CENTER = 0X10;
        /// <summary>
        /// Hides the window. By default, the window is shown.
        /// </summary>
        public const int AW_HIDE = 0X10000;
        /// <summary>
        /// Activates the window.
        /// </summary>
        public const int AW_ACTIVATE = 0X20000;
        /// <summary>
        /// Uses slide animation. By default, roll animation is used.
        /// </summary>
        public const int AW_SLIDE = 0X40000; 
        /// <summary>
        /// Uses a fade effect. 
        /// This flag can be used only if hwnd is a top-level window.
        /// </summary>
        public const int AW_BLEND = 0X80000;
        /// <summary>
        /// Animates a window.
        /// </summary>
        [DllImport("user32.dll", CharSet=CharSet.Auto)]
        public static  extern int AnimateWindow 
		(IntPtr hwand , int dwTime , int dwFlags) ;        
    }

The Animated Child Form

The animated form has very little code in the Load event, a call to the WinAPI class's static implementation of the original API.

What's more, the form can be animated when it appears and/or disappears.

WinAPI.AnimateWindow (this.Handle, animationTime, flags);

The Parent Form

The parent form is used to set the parameters of the animation and load the animated form. There are 6 buttons in this form in total. Listed below are the types of animations:

Basic Animations
1. Roll Left to Right
2. Roll Right to Left
3. Roll Top to Bottom
4. Roll Bottom to Top
5. Roll Collapse
6. Roll Fade
Slide Effect
1. Slide Left to Right
2. Slide Right to Left
3. Slide Top to Bottom
4. Slide Bottom to Top