I realized that our nsTextStore methods check read lock flag with nsTextStore::IsReadLocked(). This means that nsTextStore allows them to work with read-write lock. However, MSDN documents said they should work with read-ONLY lock. This means that our code could become simpler than current one. IsReadLocked() is checked by: * nsTextStore::GetSelection() > http://msdn.microsoft.com/en-us/library/ms538429%28v=vs.85%29.aspx * nsTextStore::GetText() > http://msdn.microsoft.com/en-us/library/ms538433%28v=vs.85%29.aspx (see the return value's document) * nsTextStore::GetEndACP(LONG *pacp) > http://msdn.microsoft.com/en-us/library/ms538424%28v=vs.85%29.aspx (see the return value's document) * nsTextStore::GetACPFromPoint(TsViewCookie vcView, const POINT *pt, DWORD dwFlags, LONG *pacp) > http://msdn.microsoft.com/en-us/library/ms538418%28v=vs.85%29.aspx (not documented, but http://msdn.microsoft.com/en-us/library/windows/desktop/ms538780%28v=vs.85%29.aspx documents the specifying cookie must be read-only locked) * nsTextStore::GetTextExt(TsViewCookie vcView, LONG acpStart, LONG acpEnd, RECT *prc, BOOL *pfClipped) > http://msdn.microsoft.com/en-us/library/ms538435%28v=vs.85%29.aspx * nsTextStore::InsertTextAtSelection(DWORD dwFlags, const WCHAR *pchText, ULONG cch, LONG *pacpStart, LONG *pacpEnd, TS_TEXTCHANGE *pChange) > http://msdn.microsoft.com/en-us/library/ms538441%28v=vs.85%29.aspx (not documented, but http://msdn.microsoft.com/en-us/library/windows/desktop/ms628599.aspx documents it should request read-only lock before calling this with TF_IAS_QUERYONLY) So, I think that these methods should check whether (TS_LF_READ == (aLock & TS_LF_READWRITE)) or not.

InsertTextAtSelection() is not true. I misunderstand the document. The document says "read-only lock is sufficient". So, it should allow read-write lock too. However, both MS-IME and ATOK access other methods with read-write lock. If we return TS_E_NOLOCK error at that time, they won't work :-( So, I'm marking this as WONTFIX.