FireworkEffect.cs

// // Copyright (c) Microsoft. All rights reserved.
// // Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;

namespace PerFrameAnimation
{
    //uielement
    //visual operations
    //animation effect stuff
    //LayoutOverrideDecorator

    public class FireworkEffect : OverlayRenderDecorator
    {
        private readonly Vector _gravity = new Vector(0.0, 10.0);
        private readonly List<Particle> _particles = new List<Particle>();
        private Point _lastMousePosition = new Point(0, 0);
        private double _secondsUntilDrop;
        private ParticleEffectsTimeTracker _timeTracker;
        protected Random Random = new Random();

        protected override void OnAttachChild(UIElement child)
        {
            CompositionTarget.Rendering += OnFrameCallback;

            child.PreviewMouseLeftButtonUp += OnMouseLeftButtonUp;
            child.PreviewMouseMove += OnMouseMove;

            _timeTracker = new ParticleEffectsTimeTracker();
        }

        protected override void OnDetachChild(UIElement child)
        {
            CompositionTarget.Rendering -= OnFrameCallback;

            child.PreviewMouseLeftButtonUp -= OnMouseLeftButtonUp;
            child.PreviewMouseMove -= OnMouseMove;

            _timeTracker = null;
        }

        protected void OnFrameCallback(object sender, EventArgs e)
        {
            UpdateParticles(_timeTracker.Update());
        }

        protected virtual void UpdateParticles(double deltatime)
        {
            //drop particles from mouse position
            if (MouseDropsParticles && IsMouseOver)
            {
                _secondsUntilDrop -= deltatime;
                if (_secondsUntilDrop < 0.0)
                {
                    AddRandomBurst(_lastMousePosition - new Vector(Radius/2.0, Radius/2.0), 1);
                    _secondsUntilDrop = MouseDropDelay + (Random.NextDouble()*2.0 - 1.0)*MouseDropDelayVariation;
                }
            }

            if (_particles.Count > 0)
                InvalidateVisual();

            //update all particles
            for (var i = 0; i < _particles.Count;)
            {
                //_particles[i]
                var p = _particles[i];

                if (GravitateToMouse)
                {
                    p.Velocity += (_lastMousePosition - p.Location)*GravitateScale;
                }
                else
                {
                    p.Velocity += _gravity;
                }
                p.Location += p.Velocity*deltatime;

                if (BounceOffContainer)
                {
                    var radius = p.Diameter/2.0;
                    if (p.Location.X - radius < 0.0)
                    {
                        p.Location.X = radius;
                        p.Velocity.X *= -0.9;
                    }
                    else if (p.Location.X > ActualWidth - radius)
                    {
                        p.Location.X = ActualWidth - radius;
                        p.Velocity.X *= -0.9;
                    }
                    if (p.Location.Y - radius < 0.0)
                    {
                        p.Location.Y = radius;
                        p.Velocity.Y *= -0.9;
                    }
                    else if (p.Location.Y > ActualHeight - radius)
                    {
                        p.Location.Y = ActualHeight - radius;
                        p.Velocity.Y *= -0.9;
                    }
                }

                //only increment counter for live particles
                if (_timeTracker.ElapsedTime > p.DeathTime)
                    _particles.RemoveAt(i);
                else
                    i++;
            }
        }

        protected override void OnOverlayRender(DrawingContext drawingContext)
        {
            foreach (var p in _particles)
            {
                //figure out where in the particles life we are
                var particlelife = (_timeTracker.ElapsedTime - p.LifeTime).TotalSeconds/
                                   (p.DeathTime - p.LifeTime).TotalSeconds;
                var currentcolor = Color.Multiply(p.StartColor, (float) (1.0 - particlelife)) +
                                   Color.Multiply(p.EndColor, (float) particlelife);
                Brush brush = new RadialGradientBrush(currentcolor,
                    Color.FromArgb(0, currentcolor.R, currentcolor.G, currentcolor.B));

                var rect =
                    new RectangleGeometry(
                        new Rect(new Point(p.Location.X - p.Diameter/2.0, p.Location.Y - p.Diameter/2.0),
                            new Size(p.Diameter, p.Diameter)));
                drawingContext.DrawGeometry(brush, null, rect);
            }
        }

        private void OnMouseMove(object sender, MouseEventArgs e)
        {
            _lastMousePosition = e.GetPosition(this);
        }

        private void OnMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            AddRandomBurst(e.GetPosition(this));
        }

        public void AddRandomBurst()
        {
            var point = new Point(Random.NextDouble()*ActualWidth, Random.NextDouble()*ActualHeight);
            AddRandomBurst(point, ClickBurstSize);
        }

        public void AddRandomBurst(Point location)
        {
            AddRandomBurst(location, ClickBurstSize);
        }

        public void AddRandomBurst(Point location, int count)
        {
            for (var i = 0; i < count; i++)
            {
                var p = new Particle();

                var radius = Radius + (Random.NextDouble()*2.0 - 1.0)*RadiusVariation;
                var lifetime = Random.NextDouble()*3.0 + 1.0;

                p.Location = location;
                p.Velocity = new Vector(Random.NextDouble()*200.0 - 100.0, Random.NextDouble()*-200 + 100.0);
                p.LifeTime = _timeTracker.ElapsedTime;
                p.DeathTime = _timeTracker.ElapsedTime + TimeSpan.FromSeconds(lifetime);
                p.Diameter = 2.0*radius;

                var startColor = StartColor;
                var startColorVariation = StartColorVariation;
                var endColor = EndColor;
                var endColorVariation = EndColorVariation;

                var startRandColor = Color.FromScRgb(startColorVariation.ScA*(float) (Random.NextDouble()*2.0 - 1.0),
                    startColorVariation.ScR*(float) (Random.NextDouble()*2.0 - 1.0),
                    startColorVariation.ScG*(float) (Random.NextDouble()*2.0 - 1.0),
                    startColorVariation.ScB*(float) (Random.NextDouble()*2.0 - 1.0));
                var endRandColor = Color.FromScRgb(endColorVariation.ScA*(float) (Random.NextDouble()*2.0 - 1.0),
                    endColorVariation.ScR*(float) (Random.NextDouble()*2.0 - 1.0),
                    endColorVariation.ScG*(float) (Random.NextDouble()*2.0 - 1.0),
                    endColorVariation.ScB*(float) (Random.NextDouble()*2.0 - 1.0));

                p.StartColor = startColor + startRandColor;
                p.EndColor = endColor + endRandColor;
                _particles.Add(p);
            }
        }

        #region Dependency Properties

        public static readonly DependencyProperty RadiusProperty =
            DependencyProperty.Register(
                "RadiusBase",
                typeof (double),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(15.0)
                );

        public static readonly DependencyProperty RadiusVariationProperty =
            DependencyProperty.Register(
                "RadiusVariation",
                typeof (double),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(5.0)
                );

        public static readonly DependencyProperty StartColorProperty =
            DependencyProperty.Register(
                "StartColor",
                typeof (Color),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(Color.FromArgb(245, 200, 50, 20))
                );

        public static readonly DependencyProperty EndColorProperty =
            DependencyProperty.Register(
                "EndColor",
                typeof (Color),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(Color.FromArgb(100, 200, 255, 20))
                );

        public static readonly DependencyProperty StartColorVariationProperty =
            DependencyProperty.Register(
                "StartColorVariation",
                typeof (Color),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(Color.FromArgb(10, 55, 50, 20))
                );

        public static readonly DependencyProperty EndColorVariationProperty =
            DependencyProperty.Register(
                "EndColorVariation",
                typeof (Color),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(Color.FromArgb(50, 20, 100, 20))
                );

        public static readonly DependencyProperty MouseDropDelayProperty =
            DependencyProperty.Register(
                "MouseDropDelay",
                typeof (double),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(0.1)
                );

        public static readonly DependencyProperty MouseDropDelayVariationProperty =
            DependencyProperty.Register(
                "MouseDropDelayVariation",
                typeof (double),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(0.05)
                );

        public static readonly DependencyProperty ClickBurstSizeProperty =
            DependencyProperty.Register(
                "ClickBurstSize",
                typeof (int),
                typeof (FireworkEffect),
                new FrameworkPropertyMetadata(30)
                );

        #endregion

        #region Properties

        public double Radius
        {
            get { return (double) GetValue(RadiusProperty); }
            set { SetValue(RadiusProperty, value); }
        }

        public double RadiusVariation
        {
            get { return (double) GetValue(RadiusVariationProperty); }
            set { SetValue(RadiusVariationProperty, value); }
        }

        public Color StartColor
        {
            get { return (Color) GetValue(StartColorProperty); }
            set { SetValue(StartColorProperty, value); }
        }

        public Color EndColor
        {
            get { return (Color) GetValue(EndColorProperty); }
            set { SetValue(EndColorProperty, value); }
        }

        public Color StartColorVariation
        {
            get { return (Color) GetValue(StartColorVariationProperty); }
            set { SetValue(StartColorVariationProperty, value); }
        }

        public Color EndColorVariation
        {
            get { return (Color) GetValue(EndColorVariationProperty); }
            set { SetValue(EndColorVariationProperty, value); }
        }


        public bool BounceOffContainer { get; set; } = false;

        public bool GravitateToMouse { get; set; } = false;

        public double GravitateScale { get; set; } = 0.1;

        public bool MouseDropsParticles { get; set; } = false;

        public double MouseDropDelay
        {
            get { return (double) GetValue(MouseDropDelayProperty); }
            set { SetValue(MouseDropDelayProperty, value); }
        }

        public double MouseDropDelayVariation
        {
            get { return (double) GetValue(MouseDropDelayVariationProperty); }
            set { SetValue(MouseDropDelayVariationProperty, value); }
        }

        public int ClickBurstSize
        {
            get { return (int) GetValue(ClickBurstSizeProperty); }
            set { SetValue(ClickBurstSizeProperty, value); }
        }

        #endregion
    }
}