mediaclock.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / System / Windows / Media / mediaclock.cs / 2 / mediaclock.cs
                        
                        
                            //------------------------------------------------------------------------------ 
//  Microsoft Avalon
//  Copyright (c) Microsoft Corporation, 2003
//
//  File:       mediaclock.cs 
//
//----------------------------------------------------------------------------- 
using System; 
using System.Diagnostics;
using System.ComponentModel; 
using MS.Internal;
using MS.Win32;
using System.Windows.Media.Animation;
using System.Windows.Media; 
using System.Windows.Media.Composition;
using System.Windows.Markup; 
using System.Security.Permissions; 
using System.Security;
using MS.Internal.PresentationCore;                   // SecurityHelper 
using System.Windows.Threading;

using System.Runtime.InteropServices;
using System.IO; 

using SR=MS.Internal.PresentationCore.SR; 
using SRID=MS.Internal.PresentationCore.SRID; 
using UnsafeNativeMethods=MS.Win32.PresentationCore.UnsafeNativeMethods;
 
namespace System.Windows.Media
{
    #region MediaClock
 
    /// 
    /// Maintains run-time timing state for media (audio/video) objects. 
    ///  
    public class MediaClock :
        Clock 
    {
        #region Constructors and Finalizers

        ///  
        /// Creates a MediaClock object.
        ///  
        ///  
        /// The MediaTimeline to use as a template.
        ///  
        /// 
        /// The returned MediaClock doesn't have any children.
        /// 
        protected internal MediaClock(MediaTimeline media) 
            : base(media)
        {} 
 
        #endregion
 
        #region Properties

        /// 
        /// Gets the MediaTimeline object that holds the description controlling the 
        /// behavior of this clock.
        ///  
        ///  
        /// The MediaTimeline object that holds the description controlling the
        /// behavior of this clock. 
        /// 
        public new MediaTimeline Timeline
        {
            get 
            {
                return (MediaTimeline)base.Timeline; 
            } 
        }
 
        #endregion

        #region Clock Overrides
 
        /// 
        /// Returns True because Media has the potential to slip. 
        ///  
        /// True
        protected override bool GetCanSlip() 
        {
            return true;
        }
 
        /// 
        /// Get the actual media time for slip synchronization 
        ///  
        protected override TimeSpan GetCurrentTimeCore()
        { 
            if (_mediaPlayer != null)
            {
                return _mediaPlayer.Position;
            } 
            else  // Otherwise use base implementation
            { 
                return base.GetCurrentTimeCore(); 
            }
        } 

        /// 
        /// Called when we are stopped. This is the same as pausing and seeking
        /// to the beginning. 
        /// 
        protected override void Stopped() 
        { 
            // Only perform the operation if we're controlling a player
            if (_mediaPlayer != null) 
            {
                _mediaPlayer.SetSpeedRatio(0);
                _mediaPlayer.SetPosition(TimeSpan.FromTicks(0));
            } 
        }
 
        ///  
        /// Called when our speed changes. A discontinuous time movement may or
        /// may not have occurred. 
        /// 
        protected override void SpeedChanged()
        {
            Sync(); 
        }
 
        ///  
        /// Called when we have a discontinuous time movement, but no change in
        /// speed 
        /// 
        protected override void DiscontinuousTimeMovement()
        {
            Sync(); 
        }
 
        private void Sync() 
        {
            // Only perform the operation if we're controlling a player 
            if (_mediaPlayer != null)
            {
                double? currentSpeedProperty = this.CurrentGlobalSpeed;
                double currentSpeedValue = currentSpeedProperty.HasValue ? currentSpeedProperty.Value : 0; 

                TimeSpan? currentTimeProperty = this.CurrentTime; 
                TimeSpan currentTimeValue = currentTimeProperty.HasValue ? currentTimeProperty.Value : TimeSpan.Zero; 

                // If speed was potentially changed to 0, make sure we set media's speed to 0 (e.g. pause) before 
                // setting the position to the target frame.  Otherwise, the media's scrubbing mechanism would
                // not work correctly, because scrubbing requires media to be paused by the time it is seeked.
                if (currentSpeedValue == 0)
                { 
                    _mediaPlayer.SetSpeedRatio(currentSpeedValue);
                    _mediaPlayer.SetPosition(currentTimeValue); 
                } 
                else
                { 
                    // In the case where speed != 0, we first want to set the position and then the speed.
                    // This is because if we were previously paused, we want to be at the right position
                    // before we begin to play.
                    _mediaPlayer.SetPosition(currentTimeValue); 
                    _mediaPlayer.SetSpeedRatio(currentSpeedValue);
                } 
            } 
        }
 

        /// 
        /// Returns true if this timeline needs continuous frames.
        /// This is a hint that we should keep updating our time during the active period. 
        /// 
        ///  
        internal override bool NeedsTicksWhenActive 
        {
            get 
            {
                return true;
            }
        } 

        ///  
        /// The instance of media that this clock is driving 
        /// 
        internal MediaPlayer Player 
        {
            get
            {
                return _mediaPlayer; 
            }
            set 
            { 
                MediaPlayer oldPlayer = _mediaPlayer;
                MediaPlayer newPlayer = value; 

                // avoid inifite loops
                if (newPlayer != oldPlayer)
                { 
                    _mediaPlayer = newPlayer;
 
                    // Disassociate the old player 
                    if (oldPlayer != null)
                    { 
                        oldPlayer.Clock = null;
                    }

                    // Associate the new player 
                    if (newPlayer != null)
                    { 
                        newPlayer.Clock = this; 

                        Uri baseUri = ((IUriContext)Timeline).BaseUri; 

                        Uri toPlay = null;

                        // ignore pack URIs for now (see work items 45396 and 41636) 
                        if (baseUri != null
                         && baseUri.Scheme != System.IO.Packaging.PackUriHelper.UriSchemePack 
                         && !Timeline.Source.IsAbsoluteUri) 
                        {
                            toPlay = new Uri(baseUri, Timeline.Source); 
                        }
                        else
                        {
                            // 
                            // defaults to app domain base if Timeline.Source is
                            // relative 
                            // 
                            toPlay = Timeline.Source;
                        } 

                        // we need to sync to the current state of the clock
                        newPlayer.SetSource(toPlay);
 
                        SpeedChanged();
                    } 
                } 
            }
        } 

        #endregion

        #region Private Data members 

        ///  
        /// MediaPlayer -- holds all the precious resource references 
        /// 
        private MediaPlayer _mediaPlayer; 

        #endregion
    }
 
    #endregion
}; 
 

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