Implications of changing locale through native code

Question

We have a Java application that uses a native Win32 based C++/COM library. This native library uses Win32 APIs (_wsetlocale, SetThreadUILanguage, etc) to set the locale for the current process, thread, etc. Clients are allowed to use tools to establish their locale preferences for the native library, which could conceivable be different from the locale used for the JVM. For example, the JVM could start with EN-US but the COM library could then set the locale to FR-CA based on what clients have configured the locale for the COM library to be.
My question is, what are the implications of going beneath the JVM and modifying different aspects of the locale (in cases overriding it) using native APIs (I know that it is best to avoid doing this, but at this point, I just want to get a sense of what things could wrong). Based on information presented at http://java.sun.com/j2se/1.5.0/docs/guide/intl/locale.doc.html it is not clear to me as to what degree the JVM relies on the Windows OS for localization.
Since the COM library can potentially change the process wide locale using the _wsetlocale and change the UI locale using SetThreadUILanguage, etc, will it affect the results of CRT functions called by the JVM, captions of AWT UI components, and inputting text into Text fields, etc.
Any guidance is appreciated.
Ranjit

Answer 1

I have tried a few simple programs where I set the JVM's locale to FR-CA and let the COM library override it with EN-US. However, the captions on the JOptionPane still display in French and the Date object continues to print itself in French as well. I am also in the process of acquiring an MUI pack for Windows 7 to try out more experiments with different display languages.
However, since I am new to this subject I wouldn't know of corner cases to test that could be affected by mixing locales, like functionality that depends on the OS, etc, and I am hoping the group could guide me in this matter.
Thank you,
Ranjit