internal static int GetTextInRun(TextContainer textContainer, int symbolOffset, TextTreeTextNode textNode, int nodeOffset, LogicalDirection direction, char[] textBuffer, int startIndex, int count)
{
int skipCount;
int finalCount;
if (textBuffer == null)
{
throw new ArgumentNullException("textBuffer");
}
if (startIndex < 0)
{
throw new ArgumentException(SR.Get(SRID.NegativeValue, "startIndex"));
}
if (startIndex > textBuffer.Length)
{
throw new ArgumentException(SR.Get(SRID.StartIndexExceedsBufferSize, startIndex, textBuffer.Length));
}
if (count < 0)
{
throw new ArgumentException(SR.Get(SRID.NegativeValue, "count"));
}
if (count > textBuffer.Length - startIndex)
{
throw new ArgumentException(SR.Get(SRID.MaxLengthExceedsBufferSize, count, textBuffer.Length, startIndex));
}
Invariant.Assert(textNode != null, "textNode is expected to be non-null");
textContainer.EmptyDeadPositionList();
if (nodeOffset < 0)
{
skipCount = 0;
}
else
{
skipCount = (direction == LogicalDirection.Forward) ? nodeOffset : textNode.SymbolCount - nodeOffset;
symbolOffset += nodeOffset;
}
finalCount = 0;
// Loop and combine adjacent text nodes into a single run.
// This isn't just a perf optimization. Because text positions
// split text nodes, if we just returned a single node's text
// callers would see strange side effects where position.GetTextLength() !=
// position.GetText() if another position is moved between the calls.
while (textNode != null)
{
// Never return more textBuffer than the text following this position in the current text node.
finalCount += Math.Min(count - finalCount, textNode.SymbolCount - skipCount);
skipCount = 0;
if (finalCount == count)
break;
textNode = ((direction == LogicalDirection.Forward) ? textNode.GetNextNode() : textNode.GetPreviousNode()) as TextTreeTextNode;
}
// If we're reading backwards, need to fixup symbolOffset to point into the node.
if (direction == LogicalDirection.Backward)
{
symbolOffset -= finalCount;
}
if (finalCount > 0) // We may not have allocated textContainer.RootTextBlock if no text was ever inserted.
{
TextTreeText.ReadText(textContainer.RootTextBlock, symbolOffset, finalCount, textBuffer, startIndex);
}
return finalCount;
}
