//------------------------------------------------------------------------------
//  Microsoft Avalon
//  Copyright (c) Microsoft Corporation, 2005
//
//  File:       BitmapEffectDropShadow.cs
//------------------------------------------------------------------------------
 
#region Using directives
 
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security;
using SecurityHelper=MS.Internal.SecurityHelper; 
 
#endregion
 
namespace System.Windows.Media.Effects
{
    /// <summary>
    /// The class definition for DropShadowBitmapEffect
    /// </summary>
    public partial class DropShadowBitmapEffect
    {
 
        /// <summary>
        /// Constructor
        /// </summary>
        public DropShadowBitmapEffect()
        {
 
        }
 
        /// <summary>
        /// Creates the unmanaged effect handle
        /// </summary>
        /// <SecurityNote>
        /// Critical - returns a security critical type SafeHandle.
        /// Safe     - Always returns null.
        /// </SecurityNote>
        [SecuritySafeCritical]
        [Obsolete(MS.Internal.Media.VisualTreeUtils.BitmapEffectObsoleteMessage)]
        unsafe protected override SafeHandle CreateUnmanagedEffect()
        {
            return null;
        }
 
        /// <summary>
        /// /// Update (propagetes) properties to the unmanaged effect
        /// </summary>                    
        /// <SecurityNote>
        /// This method demands permission because effects should not be run
        /// in partial trust.
        /// 
        /// SecurityCritical - because SetValue has a link demand
        /// SecutiryTreatAsSafe - because it demans UIWindow permission
        /// </SecurityNote>
        [SecurityCritical, SecurityTreatAsSafe]
        [Obsolete(MS.Internal.Media.VisualTreeUtils.BitmapEffectObsoleteMessage)]
        protected override void UpdateUnmanagedPropertyState(SafeHandle unmanagedEffect)
        {
            SecurityHelper.DemandUIWindowPermission();
        }
        
        /// <summary>
        /// An ImageEffect can be used to emulate a DropShadowBitmapEffect with certain restrictions. This
        /// method returns true when it is possible to emulate the DropShadowBitmapEffect using an ImageEffect.
        /// </summary>
        internal override bool CanBeEmulatedUsingEffectPipeline()
        {
            return (Noise == 0.0);
        }
 
        /// <summary>
        /// Returns a ImageEffect that emulates this DropShadowBitmapEffect.
        /// </summary>        
        internal override Effect GetEmulatingEffect()
        {
            if (_imageEffectEmulation != null && _imageEffectEmulation.IsFrozen)
            {
                return _imageEffectEmulation;
            }
            
            if (_imageEffectEmulation == null)
            {
                _imageEffectEmulation = new DropShadowEffect();
            }
 
            Color color = Color;
            if (_imageEffectEmulation.Color != color)
            {
                _imageEffectEmulation.Color = color;
            }
            // The limits on ShadowDepth preserve existing behavior.
            // A scale transform can scale the shadow depth to exceed 50.0, 
            // and this behavior is also handled correctly in the unmanaged layer.
            double shadowDepth = ShadowDepth;
            if (_imageEffectEmulation.ShadowDepth != shadowDepth)
            {
                if (shadowDepth >= 50.0)
                {
                    _imageEffectEmulation.ShadowDepth = 50.0;
                }
                else if (shadowDepth < 0.0)
                {
                    _imageEffectEmulation.ShadowDepth = 0.0;
                }
                else
                {
                    _imageEffectEmulation.ShadowDepth = shadowDepth;
                }
            }
 
            double direction = Direction;
            if (_imageEffectEmulation.Direction != direction)
            {
                _imageEffectEmulation.Direction = direction;
            }
 
            double opacity = Opacity;
            if (_imageEffectEmulation.Opacity != opacity)
            {
                if (opacity >= 1.0)
                {
                    _imageEffectEmulation.Opacity = 1.0;
                }
                else if (opacity <= 0.0)
                {
                    _imageEffectEmulation.Opacity = 0.0;
                }
                else
                {
                    _imageEffectEmulation.Opacity = opacity;
                }
            }
 
            double softness = Softness;
            if (_imageEffectEmulation.BlurRadius / _MAX_EMULATED_BLUR_RADIUS != softness)
            {
                if (softness >= 1.0)
                {
                    _imageEffectEmulation.BlurRadius = _MAX_EMULATED_BLUR_RADIUS;
                }
                else if (softness <= 0.0)
                {
                    _imageEffectEmulation.BlurRadius = 0.0;
                }
                else
                {
                    _imageEffectEmulation.BlurRadius = _MAX_EMULATED_BLUR_RADIUS * softness;
                }
            }
 
            _imageEffectEmulation.RenderingBias = RenderingBias.Performance;
 
            if (this.IsFrozen)
            {
                _imageEffectEmulation.Freeze();
            }
 
            return _imageEffectEmulation;
        }        
 
        DropShadowEffect _imageEffectEmulation;
 
        private const double _MAX_EMULATED_BLUR_RADIUS = 25.0;
    }
}