The new book "Practical UML Statecharts in C/C++, Second Edition" will provide almost 700 pages of detailed documentation. The book is in English, but already some people expressed interest in translating it into Chinese (similarly as the first edition). I have not heard yet about plans of a Spanish translation.
Independently, all versions of the source code are coming with the reference manuals generated from the source code by Doxygen. This documentation will be offered in English only, because different language versions would require proliferating source code versions, which is unmanageable.