HostedElements.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / MS / Internal / documents / HostedElements.cs / 1 / HostedElements.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
// File: HostedElements.cs 
//
// Enumerator class for returning descendants of TextBlock and FlowDocumentPage 
// 
// History:
//  01/17/2005 : [....] - created. 
//
//---------------------------------------------------------------------------

using System.Collections; 
using MS.Internal.Documents;
using System.Collections.Generic; 
using System.Collections.ObjectModel; 
using System;
using System.Diagnostics; 

#pragma warning disable 1634, 1691  // suppressing PreSharp warnings

namespace System.Windows.Documents 
{
    ///  
    ///  Enumerator class for implementation of IContentHost on TextBlock and FlowDocumentPage. 
    ///  Used to iterate through descendants of the content host
    ///  
    internal class HostedElements : IEnumerator
    {
        //-------------------------------------------------------------------
        // 
        //  Constructors
        // 
        //------------------------------------------------------------------- 

        #region Constructors 

        internal HostedElements(ReadOnlyCollection textSegments)
        {
            _textSegments = textSegments; 
            _currentPosition = null;
            _currentTextSegment = 0; 
        } 

        #endregion Constructors 


        //--------------------------------------------------------------------
        // 
        // IDisposable Methods
        // 
        //------------------------------------------------------------------- 

        #region IDisposable Methods 

        void IDisposable.Dispose()
        {
            _textSegments = null; 
        }
 
        #endregion IDisposable Methods 

        //-------------------------------------------------------------------- 
        //
        // Private Methods
        //
        //-------------------------------------------------------------------- 

        #region Private Methods 
 
        public bool MoveNext()
        { 
            // If _textSegments has been disposed, throw exception
            if (_textSegments == null)
            {
                throw new ObjectDisposedException("HostedElements"); 
            }
 
            if (_textSegments.Count == 0) 
                return false;
 
            // Verify that current position matches with current text segment, and set it if it's null.
            if (_currentPosition == null)
            {
                // We should be at the start 
                Debug.Assert(_currentTextSegment == 0);
                // Type check that we can create _currentPosition here 
                if (_textSegments[0].Start is TextPointer) 
                {
                    _currentPosition = new TextPointer(_textSegments[0].Start as TextPointer); 
                }
                else
                {
                    // We cannot search, return false 
                    _currentPosition = null;
                    return false; 
                } 
            }
            else if (_currentTextSegment < _textSegments.Count) 
            {
                // We have not yet reached the end of the container. Assert that our position matches with
                // our current text segment
                Debug.Assert(((ITextPointer)_currentPosition).CompareTo(_textSegments[_currentTextSegment].Start) >= 0 && 
                             ((ITextPointer)_currentPosition).CompareTo(_textSegments[_currentTextSegment].End) < 0);
 
                // This means that we are in the middle of content, so the previous search would have returned 
                // something. We want to now move beyond that position
                _currentPosition.MoveToNextContextPosition(LogicalDirection.Forward); 
            }

            // Search strarting from the position in the current segment
            while (_currentTextSegment < _textSegments.Count) 
            {
                Debug.Assert(((ITextPointer)_currentPosition).CompareTo(_textSegments[_currentTextSegment].Start) >= 0); 
                while (((ITextPointer)_currentPosition).CompareTo(_textSegments[_currentTextSegment].End) < 0) 
                {
                    if (_currentPosition.GetPointerContext(LogicalDirection.Forward) == TextPointerContext.ElementStart || 
                        _currentPosition.GetPointerContext(LogicalDirection.Forward) == TextPointerContext.EmbeddedElement)
                    {
                        return true;
                    } 
                    else
                    { 
                        _currentPosition.MoveToNextContextPosition(LogicalDirection.Forward); 
                    }
                } 

                // We have reached the end of a segement. Update counters
                _currentTextSegment++;
                if (_currentTextSegment < _textSegments.Count) 
                {
                    // Move to the next segment 
                    if (_textSegments[_currentTextSegment].Start is TextPointer) 
                    {
                        _currentPosition = new TextPointer(_textSegments[_currentTextSegment].Start as TextPointer); 
                    }
                    else
                    {
                        // This state is invalid, set to null and return false 
                        _currentPosition = null;
                        return false; 
                    } 
                }
            } 
            // We have reached the end without finding an element. Return false.
            return false;
        }
 
        #endregion Private Methods
 
        //------------------------------------------------------------------- 
        //
        // Private Properties 
        //
        //--------------------------------------------------------------------

        #region Private Properties 

        object IEnumerator.Current 
        { 
            get { return this.Current; }
        } 

        void IEnumerator.Reset()
        {
            throw new NotImplementedException(); 
        }
 
        public IInputElement Current 
        {
            get 
            {
                // Disable PRESharp warning 6503: "Property get methods should not throw exceptions".
                // HostedElements must throw exception if Current property is incorrectly accessed
                if (_textSegments == null) 
                {
                    // Collection was modified 
                    #pragma warning suppress 6503 // IEnumerator.Current is documented to throw this exception 
                    throw new InvalidOperationException(SR.Get(SRID.EnumeratorCollectionDisposed));
                } 

                if (_currentPosition == null)
                {
                    // Enumerator not started. Call MoveNext to see if we can move ahead 
                    #pragma warning suppress 6503 // IEnumerator.Current is documented to throw this exception
                    throw new InvalidOperationException(SR.Get(SRID.EnumeratorNotStarted)); 
                } 

                IInputElement currentElement = null; 
                switch (_currentPosition.GetPointerContext(LogicalDirection.Forward))
                {
                    case TextPointerContext.ElementStart:
                        Debug.Assert(_currentPosition.GetAdjacentElementFromOuterPosition(LogicalDirection.Forward) is IInputElement); 
                        currentElement = _currentPosition.GetAdjacentElementFromOuterPosition(LogicalDirection.Forward);
                        break; 
                    case TextPointerContext.EmbeddedElement: 
                        Debug.Assert(_currentPosition.GetAdjacentElement(LogicalDirection.Forward) is IInputElement);
                        currentElement = (IInputElement)_currentPosition.GetAdjacentElement(LogicalDirection.Forward); 
                        break;
                    default:
                        // Throw exception because this function should only be called after MoveNext, and not
                        // if MoveNext returns false 
                        Debug.Assert(false, "Invalid state in HostedElements.cs");
                        break; 
                } 
                return currentElement;
            } 
        }

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

        #region Private Fields

        ReadOnlyCollection _textSegments; 
        TextPointer _currentPosition;
        int _currentTextSegment; 
 
        #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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