/// <summary>
/// Returns a moving position and the suggestedX value for it.
/// </summary>
/// <param name="This">TextEditor</param>
/// <param name="innerMovingPosition">Inner moving position if it has valid layout, otherwise null.</param>
/// <returns>Returns suggestedX when moving position has valid layout, Double.NaN otherwise.</returns>
private static Double GetSuggestedX(TextEditor This, out ITextPointer innerMovingPosition)
{
// When getting moving position, we need to take care of end-of-line case
// and adjust moving position according to its orientation.
innerMovingPosition = TextEditorSelection.GetMovingPositionInner(This);
// We need a non-dirty layout to walk pages.
if (!innerMovingPosition.ValidateLayout())
{
innerMovingPosition = null;
return Double.NaN; // This value is not supposed to be used by a caller.
}
if (Double.IsNaN(This._suggestedX))
{
This._suggestedX = GetAbsoluteXOffset(This.TextView, innerMovingPosition);
// If the original moving position is on the other side of a line break,
// add in the pixel width of the line break visualization.
// Note this logic implicitly only modifies suggested x when the
// selection is non-empty.
if (This.Selection.MovingPosition.CompareTo(innerMovingPosition) > 0)
{
double breakWidth = (double)innerMovingPosition.GetValue(TextElement.FontSizeProperty) * CaretElement.c_endOfParaMagicMultiplier;
FlowDirection paragraphFlowDirection = GetScopingParagraphFlowDirection(innerMovingPosition);
FlowDirection controlFlowDirection = This.UiScope.FlowDirection;
if (paragraphFlowDirection != controlFlowDirection)
{
// Adjust for X-axis flip on Paragraphs with non-default flow direction.
breakWidth = -breakWidth;
}
This._suggestedX += breakWidth;
}
}
return This._suggestedX;
}
