VisualTarget.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / System / Windows / Media / VisualTarget.cs / 2 / VisualTarget.cs
                        
                        
                            //------------------------------------------------------------------------------ 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
// 
// History:
//  01/06/2005 : [....] - Created. 
//
//-----------------------------------------------------------------------------

using System.Windows.Media; 
using System.Windows.Media.Composition;
using System.Security; 
using System.Diagnostics; 

using SR=MS.Internal.PresentationCore.SR; 
using SRID=MS.Internal.PresentationCore.SRID;

namespace System.Windows.Media
{ 
    /// 
    /// 
    ///  
    public class VisualTarget : CompositionTarget
    { 
        //---------------------------------------------------------------------
        //
        //  Constructors
        // 
        //---------------------------------------------------------------------
 
        #region Constructors 

        ///  
        /// VisualTarget
        /// 
        public VisualTarget(HostVisual hostVisual)
        { 
            if (hostVisual == null)
            { 
                throw new ArgumentNullException("hostVisual"); 
            }
 
            _hostVisual = hostVisual;
            _connected = false;
            MediaContext.RegisterICompositionTarget(Dispatcher, this);
        } 

        ///  
        /// This function gets called when VisualTarget is created on the channel 
        /// i.e. from CreateUCEResources.
        ///  
        private void BeginHosting()
        {
            Debug.Assert(!_connected);
            try 
            {
                // 
                // Initiate hosting by the specified host visual. 
                //
                _hostVisual.BeginHosting(this); 
                _connected = true;
            }
            catch
            { 
                //
                // If exception has occurred after we have registered with 
                // MediaContext, we need to unregister to properly release 
                // allocated resources.
                // NOTE: We need to properly unregister in a disconnected state 
                //
                MediaContext.UnregisterICompositionTarget(Dispatcher, this);
                throw;
            } 
        }
 
 
        internal override void CreateUCEResources(DUCE.Channel channel, DUCE.Channel outOfBandChannel)
        { 
            Debug.Assert(channel != null);
            Debug.Assert(outOfBandChannel != null);

            if (!channel.IsLayeredWindowChannel) 
            {
 
                _outOfBandChannel = outOfBandChannel; 

                // create visual target resources 
                base.CreateUCEResources(channel, outOfBandChannel);

                // Update state to propagate flags as necessary
                StateChangedCallback( 
                    new object[]
                    { 
                        HostStateFlags.None 
                    });
 
                //
                // Addref content node on the channel. We need extra reference
                // on that node so that it does not get immediately released
                // when Dispose is called. Actual release of the node needs 
                // to be synchronized with node disconnect by the host.
                // 
 
                bool resourceCreated = _contentRoot.CreateOrAddRefOnChannel(outOfBandChannel, s_contentRootType);
                Debug.Assert(!resourceCreated); 
                _contentRoot.CreateOrAddRefOnChannel(channel, s_contentRootType);

                BeginHosting();
            } 
        }
 
 
        #endregion Constructors
 
        //----------------------------------------------------------------------
        //
        //  Public Properties
        // 
        //---------------------------------------------------------------------
 
        #region Public Properties 

        ///  
        /// Returns matrix that can be used to transform coordinates from this
        /// target to the rendering destination device.
        /// 
        public override Matrix TransformToDevice 
        {
            get 
            { 
                VerifyAPIReadOnly();
                Matrix m = WorldTransform; 
                m.Invert();
                return m;
            }
        } 

        ///  
        /// Returns matrix that can be used to transform coordinates from 
        /// the rendering destination device to this target.
        ///  
        public override Matrix TransformFromDevice
        {
            get
            { 
                VerifyAPIReadOnly();
                return WorldTransform; 
            } 
        }
 
        #endregion Public Properties

        //----------------------------------------------------------------------
        // 
        //  Public Methods
        // 
        //---------------------------------------------------------------------- 

        #region Private Fields 

        /// 
        /// Dispose cleans up the state associated with HwndTarget.
        ///  
        /// 
        ///     Critical: Sets RootVisual to null 
        ///     PublicOK: This code has the same affect as removing elements in a window 
        /// 
        [SecurityCritical] 
        public override void Dispose()
        {
            try
            { 
                VerifyAccess();
 
                if (!IsDisposed) 
                {
                    if (_hostVisual != null && _connected) 
                    {
                        RootVisual = null;

                        // 
                        // Unregister this CompositionTarget from the MediaSystem.
                        // 
                        // we need to properly unregister in a disconnected state 
                        MediaContext.UnregisterICompositionTarget(Dispatcher, this);
                    } 
                }
            }
            finally
            { 
                base.Dispose();
            } 
        } 

        ///  
        /// This function gets called when VisualTarget is removed on the channel
        /// i.e. from ReleaseUCEResources.
        /// 
        private void EndHosting() 
        {
            Debug.Assert(_connected); 
            _hostVisual.EndHosting(); 
            _connected = false;
        } 

        /// 
        /// This method is used to release all uce resources either on Shutdown or session disconnect
        ///  
        internal override void ReleaseUCEResources(DUCE.Channel channel, DUCE.Channel outOfBandChannel)
        { 
            if (!channel.IsLayeredWindowChannel) 
            {
                EndHosting(); 

                _contentRoot.ReleaseOnChannel(channel);

                if (_contentRoot.IsOnChannel(outOfBandChannel)) 
                {
                    _contentRoot.ReleaseOnChannel(outOfBandChannel); 
                } 

                base.ReleaseUCEResources(channel, outOfBandChannel); 
            }
        }

        #endregion Public Methods 

        #region Internal Properties 
 

        ///  
        /// The out of band channel on our the MediaContext this
        /// resource was created.
        /// This is needed by HostVisual for handle duplication.
        ///  
        internal DUCE.Channel OutOfBandChannel
        { 
            get 
            {
                return _outOfBandChannel; 
            }
        }

 
        #endregion Internal Properties
 
        //--------------------------------------------------------------------- 
        //
        //  Private Fields 
        //
        //----------------------------------------------------------------------

        #region Private Fields 

        DUCE.Channel _outOfBandChannel; 
        private HostVisual _hostVisual; 

        // Flag indicating whether VisualTarget-HostVisual connection exists. 
        private bool _connected;

        #endregion Private Fields
    } 
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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