HPDFUnicodeGraphemeBoundaries
function HPDFUnicodeGraphemeBoundaries(const Text: UnicodeString;
CancellationToken: THPDFCancellationToken = nil;
MaximumCodeUnits: Integer = 65535): THPDFUnicodeTextBoundaries;
以零基 UTF-16 位移回傳 Unicode 17.0.0 的所有預設延伸字素邊界,含起點與終點
MaximumCodeUnits 必須在 1 到 1048576 之間;格式不正確的 UTF-16 或預算用盡會擲出 EArgumentException,取消則擲出 EHPDFOperationCancelled