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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: Base class for all nodes in the TextContainer.
//
//
using System;
using MS.Internal;
namespace System.Windows.Documents
{
#if INT_EDGE_REF_COUNT
// A container for position reference counts on a node edge.
// Since typically a node won't have any references, we
// lazy allocate an EdgeReferenceCounts only when necessary
// to save a little space on tree nodes.
internal class EdgeReferenceCounts
{
internal int BeforeStartReferenceCount
{
get { return _beforeStartReferenceCount; }
set { _beforeStartReferenceCount = value; }
}
internal virtual int AfterStartReferenceCount
{
get { return 0; }
set { Invariant.Assert(false, "Text/Object nodes have no AfterStart edge!"); }
}
internal virtual int BeforeEndReferenceCount
{
get { return 0; }
set { Invariant.Assert(false, "Text/Object nodes have no BeforeEnd edge!"); }
}
internal int AfterEndReferenceCount
{
get { return _afterEndReferenceCount; }
set { _afterEndReferenceCount = value; }
}
private int _beforeStartReferenceCount;
private int _afterEndReferenceCount;
}
// Element reference counts adds AfterStart/BeforeEnd counts.
internal class ElementEdgeReferenceCounts : EdgeReferenceCounts
{
internal override int AfterStartReferenceCount
{
get { return _afterStartReferenceCount; }
set { _afterStartReferenceCount = value; }
}
internal override int BeforeEndReferenceCount
{
get { return _beforeEndReferenceCount; }
set { _beforeEndReferenceCount = value; }
}
private int _afterStartReferenceCount;
private int _beforeEndReferenceCount;
}
#endif // INT_EDGE_REF_COUNT
// This is the base class for all TextContainer nodes. It contains no state,
// but has several abstract properties to derived class state.
//
// The vast majority of tree manipulations work with TextTreeNode rather
// than derived classes. All splay tree balancing code lives in this class.
//
// Nodes in the TextContainer live within two hierarchies. Sibling nodes are
// stored in splay trees, a type of balanced binary tree. Some nodes,
// the TextTreeRootNode and TextTreeTextElementNodes, "contain" other nodes
// which are themselves roots of splay trees. So an individual node is
// always in a splay tree along with its siblings, and it may contain
// a splay tree of its own children.
//
// For example,
//
// <Paragraph>Hi!</Paragraph><Paragraph>Fancy <Inline>text</Inline>.</Paragraph>
//
// becomes
//
// [TextTreeRootNode]
// ||
// [TextTreeTextElementNode]
// || \
// || \
// || \
// [TextTreeTextNode "Hi!"] [TextTreeTextElementNode]
// ||
// [TextTreeTextElementNode]
// / || \
// / || \
// / || \
// / || \
// / || \
// / || \
// [TextTreeTextNode "Fancy "] [TextTreeTextNode "text"] [TextTreeTextNode "."]
//
// "||" is a link from tree to tree, "|" is a link between nodes in a single tree.
//
// The splay tree algorithm relies on a balancing operation, Splay(), performed
// after each node access. It's very important to continue splaying the tree
// as nodes are accessed, or we'll have an unbalanced binary tree. If you're
// trying to figure out why the tree perf has regressed and you see deep trees,
// read up on the splay tree algorithm in your reference book of choice and
// then consider whether or not Splay() is being called appropriately from any
// new code.
internal abstract class TextTreeNode : SplayTreeNode
{
//------------------------------------------------------
//
// Protected Methods
//
//------------------------------------------------------
#region Protected Methods
#if INT_EDGE_REF_COUNT
// Sets the count of TextPositions referencing the node's left
// edge.
// Since nodes don't usually have any references, we demand allocate
// storage when needed.
protected static void SetBeforeStartReferenceCount(ref EdgeReferenceCounts edgeReferenceCounts, int value)
{
if (edgeReferenceCounts != null)
{
if (value == 0 &&
edgeReferenceCounts.AfterStartReferenceCount == 0 &&
edgeReferenceCounts.BeforeEndReferenceCount == 0 &&
edgeReferenceCounts.AfterEndReferenceCount == 0)
{
edgeReferenceCounts = null;
}
else
{
edgeReferenceCounts.BeforeStartReferenceCount = value;
}
}
else if (value != 0)
{
edgeReferenceCounts = new EdgeReferenceCounts();
edgeReferenceCounts.BeforeStartReferenceCount = value;
}
}
// Sets the count of TextPositions referencing the node's AfterStart edge.
// Since nodes don't usually have any references, we demand allocate
// storage when needed.
protected void SetAfterStartReferenceCount(ref EdgeReferenceCounts edgeReferenceCounts, int value)
{
EdgeReferenceCounts originalCounts;
if (edgeReferenceCounts != null)
{
if (value == 0 &&
edgeReferenceCounts.BeforeStartReferenceCount == 0 &&
edgeReferenceCounts.BeforeEndReferenceCount == 0 &&
edgeReferenceCounts.AfterEndReferenceCount == 0)
{
edgeReferenceCounts = null;
}
else
{
if (!(edgeReferenceCounts is ElementEdgeReferenceCounts))
{
// We need a slightly bigger object, which tracks the inner edges.
Invariant.Assert(this is TextTreeTextElementNode, "Non-element nodes should never have inner edge references!");
originalCounts = edgeReferenceCounts;
edgeReferenceCounts = new ElementEdgeReferenceCounts();
edgeReferenceCounts.BeforeStartReferenceCount = originalCounts.BeforeStartReferenceCount;
edgeReferenceCounts.AfterEndReferenceCount = originalCounts.AfterEndReferenceCount;
}
edgeReferenceCounts.AfterStartReferenceCount = value;
}
}
else if (value != 0)
{
edgeReferenceCounts = new ElementEdgeReferenceCounts();
edgeReferenceCounts.AfterStartReferenceCount = value;
}
}
// Sets the count of TextPositions referencing the node's BeforeEnd edge.
// Since nodes don't usually have any references, we demand allocate
// storage when needed.
protected void SetBeforeEndReferenceCount(ref EdgeReferenceCounts edgeReferenceCounts, int value)
{
EdgeReferenceCounts originalCounts;
if (edgeReferenceCounts != null)
{
if (value == 0 &&
edgeReferenceCounts.BeforeStartReferenceCount == 0 &&
edgeReferenceCounts.AfterStartReferenceCount == 0 &&
edgeReferenceCounts.AfterEndReferenceCount == 0)
{
edgeReferenceCounts = null;
}
else
{
if (!(edgeReferenceCounts is ElementEdgeReferenceCounts))
{
// We need a slightly bigger object, which tracks the inner edges.
Invariant.Assert(this is TextTreeTextElementNode, "Non-element nodes should never have inner edge references!");
originalCounts = edgeReferenceCounts;
edgeReferenceCounts = new ElementEdgeReferenceCounts();
edgeReferenceCounts.BeforeStartReferenceCount = originalCounts.BeforeStartReferenceCount;
edgeReferenceCounts.AfterEndReferenceCount = originalCounts.AfterEndReferenceCount;
}
edgeReferenceCounts.BeforeEndReferenceCount = value;
}
}
else if (value != 0)
{
edgeReferenceCounts = new ElementEdgeReferenceCounts();
edgeReferenceCounts.BeforeEndReferenceCount = value;
}
}
// Sets the count of TextPositions referencing the node's right
// edge.
// Since nodes don't usually have any references, we demand allocate
// storage when needed.
protected static void SetAfterEndReferenceCount(ref EdgeReferenceCounts edgeReferenceCounts, int value)
{
if (edgeReferenceCounts != null)
{
if (value == 0 &&
edgeReferenceCounts.BeforeStartReferenceCount == 0 &&
edgeReferenceCounts.AfterStartReferenceCount == 0 &&
edgeReferenceCounts.BeforeEndReferenceCount == 0)
{
edgeReferenceCounts = null;
}
else
{
edgeReferenceCounts.AfterEndReferenceCount = value;
}
}
else if (value != 0)
{
edgeReferenceCounts = new EdgeReferenceCounts();
edgeReferenceCounts.AfterEndReferenceCount = value;
}
}
#endif // INT_EDGE_REF_COUNT
#endregion Protected Methods
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
// Returns a shallow copy of this node.
// The clone is a local root with no children.
internal abstract TextTreeNode Clone();
// Returns the TextContainer containing this node.
internal TextContainer GetTextTree()
{
SplayTreeNode node;
SplayTreeNode containingNode;
node = this;
while (true)
{
containingNode = node.GetContainingNode();
if (containingNode == null)
break;
node = containingNode;
}
return ((TextTreeRootNode)node).TextContainer;
}
// Returns the closest DependencyObject scoping a given node.
// This includes the node itself and TextContainer.Parent.
internal DependencyObject GetDependencyParent()
{
SplayTreeNode node;
DependencyObject parent;
SplayTreeNode containingNode;
TextTreeTextElementNode elementNode;
node = this;
while (true)
{
elementNode = node as TextTreeTextElementNode;
if (elementNode != null)
{
parent = elementNode.TextElement;
Invariant.Assert(parent != null, "TextElementNode has null TextElement!");
break;
}
containingNode = node.GetContainingNode();
if (containingNode == null)
{
parent = ((TextTreeRootNode)node).TextContainer.Parent; // This may be null.
break;
}
node = containingNode;
}
return parent;
}
// Returns the closest Logical Tree Node to a given node, including the
// node itself and TextContainer.Parent.
internal DependencyObject GetLogicalTreeNode()
{
TextTreeObjectNode objectNode;
TextTreeTextElementNode textElementNode;
SplayTreeNode node;
SplayTreeNode containingNode;
DependencyObject logicalTreeNode;
objectNode = this as TextTreeObjectNode;
if (objectNode != null)
{
if (objectNode.EmbeddedElement is FrameworkElement)
{
return objectNode.EmbeddedElement;
}
}
node = this;
while (true)
{
textElementNode = node as TextTreeTextElementNode;
if (textElementNode != null)
{
logicalTreeNode = textElementNode.TextElement;
break;
}
containingNode = node.GetContainingNode();
if (containingNode == null)
{
logicalTreeNode = ((TextTreeRootNode)node).TextContainer.Parent;
break;
}
node = containingNode;
}
return logicalTreeNode;
}
// Returns the TextPointerContext of the node.
// If node is TextTreeTextElementNode, this method returns ElementStart
// if direction == Forward, otherwise ElementEnd if direction == Backward.
internal abstract TextPointerContext GetPointerContext(LogicalDirection direction);
// Increments the reference count of TextPositions referencing a
// particular edge of this node.
//
// If this node is a TextTreeTextNode, the increment may split the node
// and the return value is guaranteed to be the node containing the referenced
// edge (which may be a new node). Otherwise this method always returns
// the original node.
internal TextTreeNode IncrementReferenceCount(ElementEdge edge)
{
return IncrementReferenceCount(edge, +1);
}
internal virtual TextTreeNode IncrementReferenceCount(ElementEdge edge, bool delta)
{
return IncrementReferenceCount(edge, delta ? 1 : 0);
}
// Increments the reference count of TextPositions referencing a
// particular edge of this node.
//
// If this node is a TextTreeTextNode, the increment may split the node
// and the return value is guaranteed to be the node containing the referenced
// edge (which may be a new node). Otherwise this method always returns
// the original node.
internal virtual TextTreeNode IncrementReferenceCount(ElementEdge edge, int delta)
{
Invariant.Assert(delta >= 0);
if (delta > 0)
{
switch (edge)
{
case ElementEdge.BeforeStart:
this.BeforeStartReferenceCount = true;
break;
case ElementEdge.AfterStart:
this.AfterStartReferenceCount = true;
break;
case ElementEdge.BeforeEnd:
this.BeforeEndReferenceCount = true;
break;
case ElementEdge.AfterEnd:
this.AfterEndReferenceCount = true;
break;
default:
Invariant.Assert(false, "Bad ElementEdge value!");
break;
}
}
return this;
}
// Decrements the reference count of TextPositions referencing this
// node.
//
// Be careful! If this node is a TextTreeTextNode, the decrement may
// cause a merge, and this node may be removed from the tree.
internal virtual void DecrementReferenceCount(ElementEdge edge)
{
#if INT_EDGE_REF_COUNT
switch (edge)
{
case ElementEdge.BeforeStart:
this.BeforeStartReferenceCount--;
Invariant.Assert(this.BeforeStartReferenceCount >= 0, "Bad BeforeStart ref count!");
break;
case ElementEdge.AfterStart:
this.AfterStartReferenceCount--;
Invariant.Assert(this.AfterStartReferenceCount >= 0, "Bad AfterStart ref count!");
break;
case ElementEdge.BeforeEnd:
this.BeforeEndReferenceCount--;
Invariant.Assert(this.BeforeEndReferenceCount >= 0, "Bad BeforeEnd ref count!");
break;
case ElementEdge.AfterEnd:
this.AfterEndReferenceCount--;
Invariant.Assert(this.AfterEndReferenceCount >= 0, "Bad AfterEnd ref count!");
break;
default:
Invariant.Assert(false, "Bad ElementEdge value!");
break;
}
#endif // INT_EDGE_REF_COUNT
}
// Inserts a node at a specified position.
internal void InsertAtPosition(TextPointer position)
{
InsertAtNode(position.Node, position.Edge);
}
internal ElementEdge GetEdgeFromOffsetNoBias(int nodeOffset)
{
return GetEdgeFromOffset(nodeOffset, LogicalDirection.Forward);
}
internal ElementEdge GetEdgeFromOffset(int nodeOffset, LogicalDirection bias)
{
ElementEdge edge;
if (this.SymbolCount == 0)
{
// If we're pointing at a zero-width TextTreeTextNode, we need to make
// sure we get the right edge -- nodeOffset doesn't convey enough information
// for GetEdgeFromOffset to compute a correct value.
edge = (bias == LogicalDirection.Forward) ? ElementEdge.AfterEnd : ElementEdge.BeforeStart;
}
else if (nodeOffset == 0)
{
edge = ElementEdge.BeforeStart;
}
else if (nodeOffset == this.SymbolCount)
{
edge = ElementEdge.AfterEnd;
}
else if (nodeOffset == 1)
{
edge = ElementEdge.AfterStart;
}
else
{
Invariant.Assert(nodeOffset == this.SymbolCount - 1);
edge = ElementEdge.BeforeEnd;
}
return edge;
}
internal int GetOffsetFromEdge(ElementEdge edge)
{
int offset;
switch (edge)
{
case ElementEdge.BeforeStart:
offset = 0;
break;
case ElementEdge.AfterStart:
offset = 1;
break;
case ElementEdge.BeforeEnd:
offset = this.SymbolCount - 1;
break;
case ElementEdge.AfterEnd:
offset = this.SymbolCount;
break;
default:
offset = 0;
Invariant.Assert(false, "Bad ElementEdge value!");
break;
}
return offset;
}
#endregion Internal methods
//------------------------------------------------------
//
// Internal Properties
//
//------------------------------------------------------
#region Internal Properties
// Count of TextPositions referencing the node's BeforeStart edge.
internal abstract bool BeforeStartReferenceCount { get; set; }
// Count of TextPositions referencing the node's AfterStart edge.
internal abstract bool AfterStartReferenceCount { get; set; }
// Count of TextPositions referencing the node's BeforeEnd edge.
internal abstract bool BeforeEndReferenceCount { get; set; }
// Count of TextPositions referencing the node's AfterEnd edge.
internal abstract bool AfterEndReferenceCount { get; set; }
#endregion Internal Properties
}
}
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