Locking...

***Never*** use a locked surface pointer after the Unlock(),

While it works on *your* hardware, it definately will not work on certain other hardware configurations.

There''s nothing slow about the Lock()/Unlock() calls themselves -they''re there for safety reasons. The main reason why a Lock can take a while is when something else (e.g. the graphics chip) may be using the surface - the CPU cannot write to the surface while this is happening (contention issues, result often == machine freeze/blue screen).
Another thing which often takes place inside the Lock() is "swizzling" - graphics hardware usually stores surfaces in a different way than you thing, i.e. not linear - the pixels are rearranged for faster hardware access. When you lock, you expect linear RGB pixels, the Lock call converts from the internal format into this. The unlock call does the reverse.

In short, don''t use the pointer after the lock!

--
Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com