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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// Description: The root node of a TextBlock splay tree.
//
using MS.Internal;
namespace System.Windows.Documents
{
// The root node of a TextBlock splay tree.
internal class TextTreeRootTextBlock : SplayTreeNode
{
//------------------------------------------------------
//
// Constructors
//
//------------------------------------------------------
#region Constructors
// Creates a TextTreeRootTextBlock instance.
internal TextTreeRootTextBlock()
{
TextTreeTextBlock block;
// Allocate an initial block with just two characters -- one for
// each edge of the root node. The block will grow when/if
// additional content is added.
block = new TextTreeTextBlock(2);
block.InsertAtNode(this, ElementEdge.AfterStart);
}
#endregion Constructors
//------------------------------------------------------
//
// Public Methods
//
//------------------------------------------------------
#region Public Methods
#if DEBUG
// Debug-only ToString override.
public override string ToString()
{
return ("RootTextBlock Id=" + this.DebugId);
}
#endif // DEBUG
#endregion Public Methods
//------------------------------------------------------
//
// Internal Properties
//
//------------------------------------------------------
#region Internal Properties
// The root node never has a parent node.
internal override SplayTreeNode ParentNode
{
get
{
return null;
}
set
{
Invariant.Assert(false, "Can't set ParentNode on TextBlock root!");
}
}
// Root node of a contained tree, if any.
internal override SplayTreeNode ContainedNode
{
get
{
return _containedNode;
}
set
{
_containedNode = (TextTreeTextBlock)value;
}
}
// The root node never has sibling nodes, so the LeftSymbolCount is a
// constant zero.
internal override int LeftSymbolCount
{
get
{
return 0;
}
set
{
Invariant.Assert(false, "TextContainer root is never a sibling!");
}
}
// Count of unicode chars of all siblings preceding this node.
// This property is only used by TextTreeNodes.
internal override int LeftCharCount
{
get
{
return 0;
}
set
{
Invariant.Assert(value == 0);
}
}
// The root node never has siblings, so it never has child nodes.
internal override SplayTreeNode LeftChildNode
{
get
{
return null;
}
set
{
Invariant.Assert(false, "TextBlock root never has sibling nodes!");
}
}
// The root node never has siblings, so it never has child nodes.
internal override SplayTreeNode RightChildNode
{
get
{
return null;
}
set
{
Invariant.Assert(false, "TextBlock root never has sibling nodes!");
}
}
// The tree generation. Not used for TextTreeRootTextBlock.
internal override uint Generation
{
get
{
return 0;
}
set
{
Invariant.Assert(false, "TextTreeRootTextBlock does not track Generation!");
}
}
// Cached symbol offset. The root node is always at offset zero.
internal override int SymbolOffsetCache
{
get
{
return 0;
}
set
{
Invariant.Assert(false, "TextTreeRootTextBlock does not track SymbolOffsetCache!");
}
}
// Not used for TextTreeRootTextBlock.
internal override int SymbolCount
{
get
{
return -1;
}
set
{
Invariant.Assert(false, "TextTreeRootTextBlock does not track symbol count!");
}
}
// Count of unicode chars covered by this node and any contained nodes.
// This property is only used by TextTreeNodes.
internal override int IMECharCount
{
get
{
return 0;
}
set
{
Invariant.Assert(value == 0);
}
}
#endregion Internal Properties
//------------------------------------------------------
//
// Private Fields
//
//------------------------------------------------------
#region Private Fields
// Root node of a contained tree, if any.
private TextTreeTextBlock _containedNode;
#endregion Private Fields
}
}
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