// Returns the symbol type preceding thisPosition.
internal static TextPointerContext GetPointerContextBackward(TextTreeNode node, ElementEdge edge)
{
TextPointerContext symbolType;
TextTreeNode previousNode;
TextTreeNode lastChildNode;
switch (edge)
{
case ElementEdge.BeforeStart:
previousNode = (TextTreeNode)node.GetPreviousNode();
if (previousNode != null)
{
symbolType = previousNode.GetPointerContext(LogicalDirection.Backward);
}
else
{
// The root node is special, there's no ElementStart/End, so test for null parent.
Invariant.Assert(node.GetContainingNode() != null, "Bad position!"); // Illegal to be at root BeforeStart.
symbolType = (node.GetContainingNode() is TextTreeRootNode) ? TextPointerContext.None : TextPointerContext.ElementStart;
}
break;
case ElementEdge.AfterStart:
// The root node is special, there's no ElementStart/End, so test for null parent.
Invariant.Assert(node.ParentNode != null || node is TextTreeRootNode, "Inconsistent node.ParentNode");
symbolType = (node.ParentNode != null) ? TextPointerContext.ElementStart : TextPointerContext.None;
break;
case ElementEdge.BeforeEnd:
lastChildNode = (TextTreeNode)node.GetLastContainedNode();
if (lastChildNode != null)
{
symbolType = lastChildNode.GetPointerContext(LogicalDirection.Backward);
}
else
{
goto case ElementEdge.AfterStart;
}
break;
case ElementEdge.AfterEnd:
symbolType = node.GetPointerContext(LogicalDirection.Backward);
break;
default:
Invariant.Assert(false, "Unknown ElementEdge value");
symbolType = TextPointerContext.Text;
break;
}
return symbolType;
}
internal static TextPointerContext GetPointerContextForward(TextTreeNode node, ElementEdge edge)
{
TextTreeNode nextNode;
TextTreeNode firstContainedNode;
TextPointerContext symbolType;
switch (edge)
{
case ElementEdge.BeforeStart:
symbolType = node.GetPointerContext(LogicalDirection.Forward);
break;
case ElementEdge.AfterStart:
if (node.ContainedNode != null)
{
firstContainedNode = (TextTreeNode)node.GetFirstContainedNode();
symbolType = firstContainedNode.GetPointerContext(LogicalDirection.Forward);
}
else
{
goto case ElementEdge.BeforeEnd;
}
break;
case ElementEdge.BeforeEnd:
// The root node is special, there's no ElementStart/End, so test for null parent.
Invariant.Assert(node.ParentNode != null || node is TextTreeRootNode, "Inconsistent node.ParentNode");
symbolType = (node.ParentNode != null) ? TextPointerContext.ElementEnd : TextPointerContext.None;
break;
case ElementEdge.AfterEnd:
nextNode = (TextTreeNode)node.GetNextNode();
if (nextNode != null)
{
symbolType = nextNode.GetPointerContext(LogicalDirection.Forward);
}
else
{
// The root node is special, there's no ElementStart/End, so test for null parent.
Invariant.Assert(node.GetContainingNode() != null, "Bad position!"); // Illegal to be at root AfterEnd.
symbolType = (node.GetContainingNode() is TextTreeRootNode) ? TextPointerContext.None : TextPointerContext.ElementEnd;
}
break;
default:
Invariant.Assert(false, "Unreachable code.");
symbolType = TextPointerContext.Text;
break;
}
return symbolType;
}
