DrawingAttributesDefaultValueFactory.cs source code in C# .NET

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Code:

                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / MS / Internal / Ink / DrawingAttributesDefaultValueFactory.cs / 1 / DrawingAttributesDefaultValueFactory.cs
                        

                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: DefaultValueFactory for DrawingAttributes 
// 
// History:
//  2005/11/08 : [....] - Created 
//
//---------------------------------------------------------------------------

using System; 
using System.Diagnostics;
using System.Windows; 
using System.Windows.Controls; 
using System.Windows.Ink;
 
namespace MS.Internal.Ink
{
    internal class DrawingAttributesDefaultValueFactory : DefaultValueFactory
    { 
        internal DrawingAttributesDefaultValueFactory()
        { 
        } 

        ///  
        ///     Returns an "immutable" default value. Since we can't make the default value
        ///     read only we'll return a new one every time.
        /// 
        internal override object DefaultValue 
        {
            get 
            { 
                return new DrawingAttributes();
            } 
        }

        /// 
        ///     Creates a mutable default value 
        /// 
        internal override object CreateDefaultValue(DependencyObject owner, DependencyProperty property) 
        { 
            // Instantiate our default value instance.
            DrawingAttributes defaultValue = new DrawingAttributes(); 

            // Add event handlers for tracking the changes on the default value instance.
            DrawingAttributesDefaultPromoter promoter = new DrawingAttributesDefaultPromoter((InkCanvas)owner);
 
            defaultValue.AttributeChanged += new PropertyDataChangedEventHandler(promoter.OnDrawingAttributesChanged);
            defaultValue.PropertyDataChanged += new PropertyDataChangedEventHandler(promoter.OnDrawingAttributesChanged); 
 
            return defaultValue;
        } 

        /// 
        /// A tracking class which monitors the sub-property changes on DrawingAttributes
        ///  
        private class DrawingAttributesDefaultPromoter
        { 
            ///  
            /// Constructor
            ///  
            /// 
            internal DrawingAttributesDefaultPromoter(InkCanvas owner)
            {
                _owner = owner; 
            }
 
            ///  
            /// A handler for both AttributeChanged and PropertyDataChanged.
            ///  
            /// 
            /// 
            internal void OnDrawingAttributesChanged(object sender, PropertyDataChangedEventArgs e)
            { 
                DrawingAttributes value = (DrawingAttributes)sender;
 
                // The current instance will be promoted to the local value other than the default value. 
                // Then we could just remove our handlers to stop tracking.
                value.AttributeChanged -= new PropertyDataChangedEventHandler(OnDrawingAttributesChanged); 
                value.PropertyDataChanged -= new PropertyDataChangedEventHandler(OnDrawingAttributesChanged);

                //
 
                if (_owner.ReadLocalValue(InkCanvas.DefaultDrawingAttributesProperty) == DependencyProperty.UnsetValue)
                { 
                    // Promote the instance to the local value. 
                    _owner.SetValue(InkCanvas.DefaultDrawingAttributesProperty, value);
                } 

                // Remove this value from the DefaultValue cache so we stop
                // handing it out as the default value now that it has changed.
                PropertyMetadata metadata = InkCanvas.DefaultDrawingAttributesProperty.GetMetadata(_owner.DependencyObjectType); 
                metadata.ClearCachedDefaultValue(_owner, InkCanvas.DefaultDrawingAttributesProperty);
            } 
 
            private readonly InkCanvas _owner;
        } 
    }
}

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

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