/// <summary>
/// Perform the Unicode Bidi algorithm.
/// </summary>
/// <param name="text">The text that the Bidi algorithm will be performed on</param>
/// <param name="paraLevel">Specifies the default level for the text; it is typically 0 (LTR) or 1 (RTL)</param>
/// <param name="embeddingLevels">May be used to preset the embedding and override levels, ignoring characters like LRE and PDF in the text;
/// a level overrides the directional property of its corresponding (same index) character if the level has the UBIDI_LEVEL_OVERRIDE bit set</param>
/// <remarks>
/// This function takes a piece of plain text containing one or more paragraphs, with or without externally specified embedding levels from styled
/// text and computes the left-right-directionality of each character.
///
/// If the entire text is all of the same directionality, then the function may not perform all the steps described by the algorithm, i.e.,
/// some levels may not be the same as if all steps were performed.This is not relevant for unidirectional text.
///
/// For example, in pure LTR text with numbers the numbers would get a resolved level of 2 higher than the surrounding text according to the
/// algorithm.This implementation may set all resolved levels to the same value in such a case.
///
/// The text can be composed of multiple paragraphs. Occurrence of a block separator in the text terminates a paragraph, and whatever comes
/// next starts a new paragraph.The exception to this rule is when a Carriage Return (CR) is followed by a Line Feed (LF). Both CR and LF are
/// block separators, but in that case, the pair of characters is considered as terminating the preceding paragraph, and a new paragraph will
/// be started by a character coming after the LF.
/// </remarks>
public void SetPara(string text, byte paraLevel, byte[] embeddingLevels)
{
if (_para != IntPtr.Zero)
{
Marshal.FreeHGlobal(_para);
_para = IntPtr.Zero;
}
if (text == null)
{
throw new ArgumentNullException(nameof(text));
}
// icu BiDi expects the para pointer to live for the life of the structure, so we have to stash it
_para = Marshal.StringToHGlobalUni(text);
NativeMethods.ubidi_setPara(_biDi, _para, text.Length, paraLevel, embeddingLevels, out var errorCode);
ExceptionFromErrorCode.ThrowIfError(errorCode, "BiDi analysis failed! " + errorCode);
}
