HostedElements.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / MS / Internal / documents / HostedElements.cs / 1305600 / 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; 
            GC.SuppressFinalize(this);
        } 
 
        #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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