VisualBrush.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / Windows / Media / VisualBrush.cs / 1305600 / VisualBrush.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
// File: VisualBrush.cs 
//
// Description: This file contains the implementation of VisualBrush. 
//              The VisualBrush is a TileBrush which defines its tile content 
//              by use of a Visual.
// 
// History:
//
//---------------------------------------------------------------------------
 
using System;
using System.ComponentModel; 
using System.Diagnostics; 
using System.Runtime.InteropServices;
using System.Security; 
using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Media3D;
using System.Windows.Media.Animation; 
using System.Windows.Media.Composition;
using System.Windows.Threading; 
using MS.Internal; 

namespace System.Windows.Media 
{
    /// 
    /// VisualBrush - This TileBrush defines its content as a Visual
    ///  
    public sealed partial class VisualBrush : TileBrush, ICyclicBrush
    { 
        #region Constructors 

        ///  
        /// Default constructor for VisualBrush.  The resulting Brush has no content.
        /// 
        public VisualBrush()
        { 

        } 
 
        /// 
        /// VisualBrush Constructor where the image is set to the parameter's value 
        /// 
        ///  The Visual representing the contents of this Brush. 
        public VisualBrush(Visual visual)
        { 
            if (this.Dispatcher != null)
            { 
                MediaSystem.AssertSameContext(this, visual); 
                Visual = visual;
            } 
        }
        #endregion Constructors

        void ICyclicBrush.FireOnChanged() 
        {
            // Simple loop detection to avoid stack overflow in cyclic VisualBrush 
            // scenarios. This fix is only aimed at mitigating a very common 
            // VisualBrush scenario.
 
            bool canEnter = Enter();

            if (canEnter)
            { 
                try
                { 
                    _isCacheDirty = true; 
                    FireChanged();
 
                    // Register brush's visual tree for Render().
                    RegisterForAsyncRenderForCyclicBrush();
                }
                finally 
                {
                    Exit(); 
                } 
            }
        } 

        /// 
        /// Calling this will make sure that the render request
        /// is registered with the MediaContext. 
        /// 
        private void RegisterForAsyncRenderForCyclicBrush() 
        { 
            DUCE.IResource resource = this as DUCE.IResource;
 
            if (resource != null)
            {
                if ((Dispatcher != null) && !_isAsyncRenderRegistered)
                { 
                    MediaContext mediaContext = MediaContext.From(Dispatcher);
 
                    // 
                    // Only register for a deferred render if this visual brush
                    // is actually on the channel. 
                    //
                    if (!resource.GetHandle(mediaContext.Channel).IsNull)
                    {
                        // Add this handler to this event means that the handler will be 
                        // called on the next UIThread render for this Dispatcher.
                        ICyclicBrush cyclicBrush = this as ICyclicBrush; 
                        mediaContext.ResourcesUpdated += new MediaContext.ResourcesUpdatedHandler(cyclicBrush.RenderForCyclicBrush); 
                        _isAsyncRenderRegistered = true;
                    } 
                }
            }
        }
 
       void ICyclicBrush.RenderForCyclicBrush(DUCE.Channel channel, bool skipChannelCheck)
       { 
 
            Visual vVisual = Visual;
 
            // The Visual may have been registered for an asynchronous render, but may have been
            // disconnected from the VisualBrush since then.  If so, don't bother to render here, if
            // the Visual is visible it will be rendered elsewhere.
            if (vVisual != null && vVisual.CheckFlagsAnd(VisualFlags.NodeIsCyclicBrushRoot)) 
            {
                // ----------------------------------------------------------------------------------- 
                // 1) Prepare the visual for rendering. 
                //
                // Updates bounding boxes. 
                //

                vVisual.Precompute();
 

                // ----------------------------------------------------------------------------------- 
                // 2) Prepare the render context. 
                //
 
                RenderContext rc = new RenderContext();

                rc.Initialize(channel, DUCE.ResourceHandle.Null);
 

                // ------------------------------------------------------------------------------------ 
                // 3) Compile the scene. 

                if (channel.IsConnected) 
                {
                    vVisual.Render(rc, 0);
                }
                else 
                {
                    // We can issue the release here instead of putting it in queue 
                    // since we are already in Render walk. 
                    ((DUCE.IResource)vVisual).ReleaseOnChannel(channel);
                } 
            }

            _isAsyncRenderRegistered = false;
        } 

 
        // Implement functions used to addref and release resources in codegen that need 
        // to be specialized for Visual which doesn't implement DUCE.IResource
        internal void AddRefResource(Visual visual, DUCE.Channel channel) 
        {
            if (visual != null)
            {
                visual.AddRefOnChannelForCyclicBrush(this, channel); 
            }
        } 
 
        internal void ReleaseResource(Visual visual, DUCE.Channel channel)
        { 
            if (visual != null)
            {
                visual.ReleaseOnChannelForCyclicBrush(this, channel);
            } 
        }
 
        ///  
        /// Implementation of DependencyObject.OnPropertyInvalidated.
        /// If the property is the Visual or the AutoLayoutContent property, we re-layout the Visual if 
        /// possible.
        /// 
        protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
        { 
            base.OnPropertyChanged(e);
 
            if (e.IsAValueChange || e.IsASubPropertyChange) 
            {
                if ((e.Property == VisualProperty) || (e.Property == AutoLayoutContentProperty)) 
                {
                    // Should we initiate a layout on this Visual?
                    // Yes, if AutoLayoutContent is true and if the Visual is a UIElement not already in
                    // another tree (i.e. the parent is null) or its not the hwnd root. 
                    if (AutoLayoutContent)
                    { 
                        Debug.Assert(!_pendingLayout); 
                        UIElement element = Visual as UIElement;
 
                        if ((element != null)
                              &&
                              ((VisualTreeHelper.GetParent(element) == null && !(element.IsRootElement))
                               || (VisualTreeHelper.GetParent(element) is Visual3D))) 
                        {
                            // 
                            // We need 2 ways of initiating layout on the VisualBrush root. 
                            // 1. We add a handler such that when the layout is done for the
                            // main tree and LayoutUpdated is fired, then we do layout for the 
                            // VisualBrush tree.
                            // However, this can fail in the case where the main tree is composed
                            // of just Visuals and never does layout nor fires LayoutUpdated. So
                            // we also need the following approach. 
                            // 2. We do a BeginInvoke to start layout on the Visual. This approach
                            // alone, also falls short in the scenario where if we are already in 
                            // MediaContext.DoWork() then we will do layout (for main tree), then look 
                            // at Loaded callbacks, then render, and then finally the Dispather will
                            // fire us for layout. So during loaded callbacks we would not have done 
                            // layout on the VisualBrush tree.
                            //
                            // Depending upon which of the two layout passes comes first, we cancel
                            // the other layout pass. 
                            //
                            element.LayoutUpdated += OnLayoutUpdated; 
                            _DispatcherLayoutResult = Dispatcher.BeginInvoke( 
                                DispatcherPriority.Normal,
                                new DispatcherOperationCallback(LayoutCallback), 
                                element);
                            _pendingLayout = true;
                        }
                    } 
                }
            } 
        } 

        ///  
        /// We initiate the layout on the tree rooted at the Visual to which VisualBrush points.
        /// 
        private void DoLayout(UIElement element)
        { 
            Debug.Assert(element != null);
 
            DependencyObject parent = VisualTreeHelper.GetParent(element); 
            if (!(element.IsRootElement)
                && (parent == null || parent is Visual3D)) 
            {
                //
                // PropagateResumeLayout sets the LayoutSuspended flag to false if it were true.
                // 
                UIElement.PropagateResumeLayout(null, element);
                element.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity)); 
                element.Arrange(new Rect(element.DesiredSize)); 
            }
        } 

        /// 
        /// LayoutUpdate event handler.
        ///  
        /// event sender (not used)
        /// event arguments (not used) 
        private void OnLayoutUpdated(object sender, EventArgs args) 
        {
            Debug.Assert(_pendingLayout); 

            // Visual has to be a UIElement since the handler was added to it.
            UIElement element = (UIElement)Visual;
            Debug.Assert(element != null); 

            // Unregister for the event 
            element.LayoutUpdated -= OnLayoutUpdated; 
            _pendingLayout = false;
 
            //
            // Since we are in this function that means that layoutUpdated fired before
            // Dispatcher.BeginInvoke fired. So we can abort the DispatcherOperation as
            // we will do the layout here. 
            //
            Debug.Assert(_DispatcherLayoutResult != null); 
            Debug.Assert(_DispatcherLayoutResult.Status == DispatcherOperationStatus.Pending); 
            bool abortStatus = _DispatcherLayoutResult.Abort();
            Debug.Assert(abortStatus); 

            DoLayout(element);
        }
 

        ///  
        /// DispatcherOperation callback to initiate layout. 
        /// 
        /// The Visual root 
        private object LayoutCallback(object arg)
        {
            Debug.Assert(_pendingLayout);
 
            UIElement element = arg as UIElement;
            Debug.Assert(element != null); 
 
            //
            // Since we are in this function that means that Dispatcher.BeginInvoke fired 
            // before LayoutUpdated fired. So we can remove the LayoutUpdated handler as
            // we will do the layout here.
            //
            element.LayoutUpdated -= OnLayoutUpdated; 
            _pendingLayout = false;
 
            DoLayout(element); 

            return null; 
        }

        /// 
        /// Enter is used for simple cycle detection in VisualBrush. If the method returns false 
        /// the brush has already been entered and cannot be entered again. Matching invocation of Exit
        /// must be skipped if Enter returns false. 
        ///  
        internal bool Enter()
        { 
            if (_reentrancyFlag)
            {
                return false;
            } 
            else
            { 
                _reentrancyFlag = true; 
                return true;
            } 
        }

        /// 
        /// Exits the VisualBrush. For more details see Enter method. 
        /// 
        internal void Exit() 
        { 
            Debug.Assert(_reentrancyFlag); // Exit must be matched with Enter. See Enter comments.
            _reentrancyFlag = false; 
        }

        /// 
        /// Obtains the current bounds of the brush's content 
        /// 
        ///  Output bounds of content 
        protected override void GetContentBounds(out Rect contentBounds) 
        {
            // Obtain the current visual's outer space bounding box. We return the outer space 
            // bounding box because we want to have the bounding box of the Visual tree including
            // transform/offset at the root.
            if (_isCacheDirty)
            { 
                _bbox = Visual.CalculateSubgraphBoundsOuterSpace();
                _isCacheDirty = false; 
            } 

            contentBounds = _bbox; 
        }

        private DispatcherOperation _DispatcherLayoutResult;
        private bool _pendingLayout; 
        private bool _reentrancyFlag;
 
        private bool _isAsyncRenderRegistered = false; 

        // Whether we need to re-calculate our content bounds. 
        private bool _isCacheDirty = true;

        // Keep our content bounds cached.
        private Rect _bbox = Rect.Empty; 
    }
} 
 

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