/// <summary>
/// Returns a TextPointer at a new position by a specified symbol
/// count.
/// </summary>
/// <param name="offset">
/// Number of symbols to advance. offset may be negative, in which
/// case the TextPointer is moved backwards.
/// </param>
/// <param name="direction">
/// LogicalDirection desired for a returned TextPointer.
/// </param>
/// <returns>
/// TextPointer located at requested position in case if requested position
/// does exist, otherwize returns null. LogicalDirection of the TextPointer
/// returned is as specified by a <paramref name="direction"/>.
/// </returns>
/// <remarks>
/// <para>This method, like all other TextPointer methods, defines a symbol
/// as one of:</para>
/// <para>- 16 bit Unicode character.</para>
/// <para>- opening or closing tag of a <see cref="TextElement"/>.</para>
/// <para>- the whole <see cref="UIElement"/> as atomic embedded object.</para>
/// <para>See examples in <seealso cref="TextPointer.GetPositionAtOffset(int)"/> method with one parameter.</para>
/// </remarks>
public TextPointer GetPositionAtOffset(int offset, LogicalDirection direction)
{
TextPointer position = new TextPointer(this, direction);
int actualCount = position.MoveByOffset(offset);
if (actualCount == offset)
{
position.Freeze();
return position;
}
else
{
return null;
}
}
// Notify our TextContainer that a typographic property has changed
// value on this TextElement.
// This has the side effect of invalidating layout.
internal void NotifyTypographicPropertyChanged(bool affectsMeasureOrArrange, bool localValueChanged, DependencyProperty property)
{
if (!this.IsInTree) // No work to do if no one's listening.
{
return;
}
TextContainer tree;
TextPointer beforeStart;
tree = EnsureTextContainer();
// Take note that something layout related has changed.
tree.NextLayoutGeneration();
// Notify any external listeners.
if (tree.HasListeners)
{
// Get the position before the start of this element.
beforeStart = new TextPointer(tree, _textElementNode, ElementEdge.BeforeStart, LogicalDirection.Forward);
beforeStart.Freeze();
// Raise ContentAffected event that spans entire TextElement (from BeforeStart to AfterEnd).
tree.BeginChange();
try
{
tree.BeforeAddChange();
if (localValueChanged)
{
tree.AddLocalValueChange();
}
tree.AddChange(beforeStart, _textElementNode.SymbolCount, _textElementNode.IMECharCount,
PrecursorTextChangeType.PropertyModified, property, !affectsMeasureOrArrange);
}
finally
{
tree.EndChange();
}
}
}
/// <summary>
/// Returns a TextPointer at the start of line after skipping
/// a given number of line starts in forward or backward direction.
/// </summary>
/// <param name="count">
/// Offset of the destination line. Negative values specify preceding
/// lines, zero specifies the current line, positive values specify
/// following lines.
/// </param>
/// <param name="actualCount">
/// The offset of the line moved to. This value may be less than
/// requested if the beginning or end of document is encountered.
/// </param>
/// <returns>
/// TextPointer positioned at the begining of a line requested
/// (with LogicalDirection set to Forward).
/// If there is no sufficient lines in requested direction,
/// returns a position at the beginning of a farthest line
/// in this direction. In such case out parameter actualCount
/// gets a number of lines actually skipped.
/// Unlike the other override in this case the returned pointer is never null.
/// </returns>
/// <remarks>
/// If this TextPointer is at an otherwise ambiguous position, exactly
/// between two lines, the LogicalDirection property is used to determine
/// current position. So a TextPointer with backward LogicalDirection
/// is considered to be at the end of line, and calling MoveToLineBoundary(0)
/// would reposition it at the start of the preceding line. Making the
/// same call with forward LogicalDirection would leave the TextPointer
/// positioned where it started -- at the start of the following line.
/// </remarks>
public TextPointer GetLineStartPosition(int count, out int actualCount)
{
this.ValidateLayout();
TextPointer position = new TextPointer(this);
if (this.HasValidLayout)
{
actualCount = position.MoveToLineBoundary(count);
}
else
{
actualCount = 0;
}
position.SetLogicalDirection(LogicalDirection.Forward);
position.Freeze();
return position;
}
